rus
Issue #2/2025
V. P. Birukov, Ya. А. Gorunov, А. N. Miryakha
Determination of Mechanical and Tribotechnical Characteristics of Coatings in Laser Broadband Cladding of Steels
Determination of Mechanical and Tribotechnical Characteristics of Coatings in Laser Broadband Cladding of Steels
DOI: 10.22184/1993-7296.FRos.2025.19.2.130.140
The paper considers the results of metallographic and tribotechnical tests of 20X13 steel samples and 20X13 steel samples with laser broadband cladding with 20X13 powder. The deposited layer had a dendritic differently oriented structure. The microhardness of the coating was 501–575 HV. It was found that the wear rate of the cladded coating is 3.16 times lower than that of the base material. The wear rate of the counter sample made of hardened steel 45 was lower in the friction pair with the cladded sample compared to the base material. The average friction factors for the cladded samples were 0.043, and for the base material was 0.078. The performance of broadband laser cladding is 5–7 times higher than when processing with a defocused beam.
The paper considers the results of metallographic and tribotechnical tests of 20X13 steel samples and 20X13 steel samples with laser broadband cladding with 20X13 powder. The deposited layer had a dendritic differently oriented structure. The microhardness of the coating was 501–575 HV. It was found that the wear rate of the cladded coating is 3.16 times lower than that of the base material. The wear rate of the counter sample made of hardened steel 45 was lower in the friction pair with the cladded sample compared to the base material. The average friction factors for the cladded samples were 0.043, and for the base material was 0.078. The performance of broadband laser cladding is 5–7 times higher than when processing with a defocused beam.
Теги: friction factor laser cladding microhardness wear rate интенсивность изнашивания коэффициент трения лазерная наплавка микротвердость
Determination of Mechanical and Tribotechnical Characteristics of Coatings in Laser Broadband Cladding of Steels
V. P. Birukov 1, Ya. А. Gorunov 1, А. N. Miryakha 2
Mechanical Engineering Research Institute of the RAS (IMASH RAS), Moscow, Russia
RME INJECT LLC, Saratov, Russia
The paper considers the results of metallographic and tribotechnical tests of 20X13 steel samples and 20X13 steel samples with laser broadband cladding with 20X13 powder. The deposited layer had a dendritic differently oriented structure. The microhardness of the coating was 501–575 HV. It was found that the wear rate of the cladded coating is 3.16 times lower than that of the base material. The wear rate of the counter sample made of hardened steel 45 was lower in the friction pair with the cladded sample compared to the base material. The average friction factors for the cladded samples were 0.043, and for the base material was 0.078. The performance of broadband laser cladding is 5–7 times higher than when processing with a defocused beam.
Key words: laser cladding, microhardness, wear rate, friction factor
The article received on: January 13, 2025
The article accepted on February 03, 2025
Introduction
The development of new laser powder cladding technologies is an important task of modern mechanical engineering. The following are the research materials conducted by foreign and domestic authors in the field of developing laser cladding technologies. AISI 1020 steel (0.18–0.23%C) was chosen as the base material for [1] samples with dimensions 76.0 × 25.4 × 10.0 mm. Ni-Cr-B-Si powder with a particle size of 53–150 microns of the 1545–00 grade with a declared hardness of 490 HV30 and a density of 7.1 g/cm3 was used for laser cladding. The samples were cladded using an IPG PHOTONICS fiber laser source at radiation power of 1.05, 1.4, 1.75 kW, beam travel speeds of 5 (C1), 21.7 (C2), 30 (C3) mm/sec, a track overlap coefficient of 30%. The samples were tested for abrasive wear according to the ASTM G65 standard according to the scheme: “annular surface of an elastic circle – a flat sample (base material, coating)” with quartz sand being gravity-fed into the friction zone. The results of the abrasive wear tests showed that samples C1 had maximum abrasive resistance, followed by samples C2 and C3 in descending order of abrasive resistance. Transverse cracks were found on samples C2 and C3, which, according to the authors, could have been prevented by preheating the samples.
For the production of samples [2], 45 steel was chosen, which was widely used in the manufacture of hydraulic cylinders. A standard 316L grade metal powder with a particle size of 53–150 microns was used for laser cladding. The samples were processed using a disk laser (TruDisk 4002, Germany) with a wavelength of 1030 nm in an environment of protective gas, argon with a flow rate of 10 l/min at room temperature, a radiation power of 2600 W, a scanning speed of 10 mm/s and a 50% overlap coefficient of the cladding tracks. Tribotechnical tests were carried out according to the scheme: “a ball (Si3N4, 4 mm in diameter with a hardness of 78 HRC) is a flat sample) at a load of 5 N and a rotational speed of 100 min‑1 with a cycle duration of 30 min. Disc samples with a diameter of 40 mm and a thickness of 10 mm were produced for wear and corrosion resistance tests. The samples were heated in a salt bath at a temperature of 1050 °C for 1 hour in a heat treatment furnace followed by air cooling. The microhardness of the deposited coatings was 170–200 HV, and after heating in a salt bath it was 240–280 HV. The increased corrosion resistance of the deposited layer with 316L powder treated in a salt furnace was explained by an increase in the microhardness of the surface. The typical mechanism of destruction during corrosion wear was abrasive wear and plastic deformation, while the main mechanism of destruction under normal wear conditions was brittle fracture of microzones and abrasive wear. The corrosive environment accelerated the wear process by about 3 times compared to what happened without the corrosive effect.
For experiments [3] on laser cladding, 27SiMn steel samples with a diameter of 150 mm and a thickness of 60 mm were used. An iron-based alloy with Cr, Ni and Si additives (average hardness 51 HRC) with an average particle size of 38 microns of spherical shape was used as a cladding powder, which ensured its better fluidity. The samples were cladded using an RFL–C4000 laser installation (Raycus Fiber Laser, Wuhan, China) – with coaxial argon powder supply, which was also used to protect molten metal at a laser power of 2.7 kW and a track overlap of 80%. Tribotechnical tests were carried out on a multifunctional friction machine (CFT-I, Zhongkekaihua, Lanzhou, China) without lubricant according to the scheme: “ball (Si3N4, diameter 5 mm) – coated sample” at a normal load of 30 N, the rotation speed of 500 min–1, and the cycle time of 30 min. To determine the characteristics of the cladded coating, samples of two types were produced: A (the upper region of the cladded layer, the thickness of which was 1.1 mm) and B (the middle region of the lining layer, the thickness from the substrate after cutting was 0.55 mm). The cladded layer of sample A contained more metal compounds and carbide phases with fine grains, and the structure of sample B consisted mainly of elongated dendrites. The microhardness of sample B was higher than that of sample A. The abrasion resistance of sample B was about 2.7 times higher than that of sample A. The mechanism of wear of sample A consisted in adhesive and abrasive wear, and for sample B in abrasive wear.
An SS316L stainless steel plate with dimensions of 100×20×60 mm was used as a substrate [4].
WC-NiCrMo powder with a spherical particle size of 30–53 microns was used for laser cladding. A diode laser system with flexible fiber LDF400–2000 (1600 W) with a round spot with a diameter of 4 mm and a diode laser system FL-DLight‑3000-976 (2400 W) with a rectangular spot of 12×2 mm were used for cladding. The laser scanning rate was 420 mm/min for the first and 180 mm/min for the second samples, with a powder consumption of 10 g/min for both coatings. 10 tracks were cladded with an overlap factor of 50%. Metallographic tests have established that the width and height of the cladded rollers for a round and rectangular spot were 5 and 0.86 mm, 9.2 and 1.27 mm, respectively. The maximum penetration depth of the substrate when surfaced with a circular beam was 0.62 mm, which is 6 times greater than when treated with a rectangular spot. The hardness for the first and second coatings also differed and amounted to 50 and 60 HRC, respectively. The wear resistance of the coatings was evaluated during wear tests according to the scheme: “ball (Si3N4, 1300 HV0.2) – disc (coated sample) without lubricant at a disk rotation speed of 350 min–1, a normal load of 400 g, and a cycle time of 2 hours. After the experiment was completed, a circular trace of a friction track with a diameter of 6 mm was formed on the surface of the sample. The wear resistance of the coating obtained by cladding with a rectangular spot was higher than after cladding with a circular beam.
Samples [5] made of stainless steel 0Cr17Ni12Mo2 with dimensions of 300×120×10 mm were used for laser cladding. Ni60 nickel-based powder (24–48 microns) and WC powder (16–48 microns) of 5 (1), 7.5 (2) and 10 (3) %wt were used as the charge material. Laser processing was performed on a Raycus RFL–C1000 installation equipped with a manipulator with six degrees of freedom, at laser power 800 W, a spot diameter of 1.8 mm and a scanning speed of 8 mm/s with a powder feed rate of 6.5 g/min, and argon was used to protect the zone from oxidation.
Friction and wear tests were carried out on an MPX‑3 G friction machine at temperatures of 20, 300, and 600 Celsius degrees according to the scheme: “ball (silicon nitride with a diameter of 6.35 mm) - disk” at a load of 50 N, a disk rotation speed of 400 min−1, and a cycle time of 50 minutes. In the field of laser surfacing, solid phases WC, W2C, Mn23C6, Fe3C, and Cr3Ni2SiC were observed, and the microhardness increased with increasing WC content. The friction rates increased with an increase in temperature to 300 Celsius degrees, and their decrease was observed at 600 Celsius degrees. The minimum wear rate was for the cladded coatings (1), and for coatings (2) it increased sharply, and for samples with coatings (3) it was lower than for coatings (2). Increase in temperature led to increase in the wear rate of the samples.
Rectangular samples [6] of W10V5Co4 steel were coated with W10V5Co4 powder and Si: 2%wt and B: 4%wt additives with the help of a diode laser with a radiation power of 1800 W, a 4×4 mm laser spot size, a scanning speed of 8 mm/s, and a 40% track overlap coefficient. Tests for dry sliding friction during reciprocating motion were performed using an Rtec universal tribometer (MFT‑5000) according to the scheme: “flat ladded sample-ball (aluminum oxide)” at a load of 10 N and a double stroke frequency of 200 min‑1 in accordance with the ASTM G132-96 standard. W10V5Co4Si2B4 coatings with a hardness of 908 HV0.2 had the highest wear resistance. The wear rate of these coatings was 1.5×10–8 mm3/(N·mm), which is 2.8 times lower than that of the original alloy steel W10V5Co4.
MSS 410 powders and titanium carbide TiC additives (0, 5%, 10%, 15%) were laser-cladded onto rectangular samples [7] made of Q235 steel. Before cladding, to obtain a uniform distribution, both powders had been mixed using a QM‑3SP04L ball mill with a rotation speed of 120 min‑1 for 2 hours, then dried in an oven at 100 Celsius degrees for 2 hours. TiC powders contained most of the small particles of 7 microns in size and a small number of irregularly shaped particles of 20–50 microns. Laser surfacing was performed at a radiation power of 480 W, a spot diameter of 1.2 mm, a travel speed of 480 mm/min, an energy density of 100 J/mm3, with a 50% cladding track overlap and a powder feed rate of 6.5 g/min. Tribotechnical experiments on coated samples were carried out on a friction machine according to the “ball-disc” scheme at room temperature. A ball made of Si3N4 (1700 HV, with a surface roughness of 0.2 microns) with a diameter of 5 mm was chosen as a counter sample. The tests were carried out at a rotational speed of 840 min‑1, a friction radius of 3 mm, a load of 10 N and a cycle time of 30 min. It was found that the microhardness and wear resistance of the coatings increased with an increase in the titanium carbide content to 10%, and microcracks were found at 15% of the TiC content, which reduced the wear resistance of the samples.
Samples [8] of AISI 1045 steel were cladded with Fe–Cr–N powder with a laser beam at a radiation power of 3 kW and a displacement speed of 5.1 mm/s. Corrosion resistance was assessed by the method of potentiodynamic polarization in a 10% NaCl solution prepared from distilled water at room temperature. The coating was resistant to corrosion, and the polarization resistance was increased six times compared to steel 1045.
Stainless steel powders 316L, 410 and 420 were used as materials for cladding of rollers [9] from wheel steel, while the counter sample rollers were made of rail steel. Laser cladding was performed at a laser beam power of 500 W, a spot diameter of 2.2 mm, a scanning speed of 10 mm/s for 316L stainless steel and 8 mm/s for 410 and 420 steel, a layer thickness of 2.2 mm, a powder feed rate of 1.2 g/min, and a protective gas flow rate of 12 l/min. To study roller wear during rolling, a “roller-roller” test scheme was applied. The rotation speed of the counter sample roller made of rail steel was 500 min‑1, the contact pressure according to Hertz was 1100 MPa, the slip coefficient was 0.75%, and the test duration was 100,000 cycles. All three coatings had low wear compared to the non-cladded rollers made from the original steel. As the hardness of the deposited materials increased, the wear rate decreased. Small surface cracks were found on the surface of individual laser-cladded samples. Deep cracks were found at the boundary between the coating and the substrate. Cracks appeared where the maximum shear stress was formed below the surface, and then they spread along the boundary between the coating and the substrate.
The use of laser cladding [10] in the repair of mining equipment is an urgent task. For laser cladding, samples of 38XMA (0.38%C) and 42XFA (0.42%C) steel and 38XMA, 42XFA and Inconel 718 powders were selected. Laser cladding was performed using the Optomec LENS 450 system, which included a laser and a powder supply system. Cylindrical rods made of 38XMA and 42XFA steel (30 mm long and 10 mm in diameter) were selected as test samples. The tribological properties of the coatings were determined with dry sliding friction according to the scheme: “pin (cladded sample or steel sample) -disc (ZrO2)” at a sliding speed of 0.52 m/s and a load of 160 N on a friction path of 300 m. Inconel 718 alloy had better mechanical and tribological properties compared to other deposited powders. The wear resistance of the cladded coatings with 38XMA and 42XFA powders was 1.7 times lower than that of the Inconel 718 powder-coated samples.
For the production of samples [11], H13 steel with dimensions of 60×50×5 mm was used. A CO2 laser with transverse pumping of gases DL2000, China, was used as equipment for laser cladding at a radiation power of 1300 W, a displacement speed of 240 mm/min, a beam diameter of 3 mm, with a track overlap of 30%. High-entropy FeCoCrNiAl alloy (WEC) powder with a particle size of 50–80 microns was used for the coating. Friction and wear tests of H13 steel samples and WEC coated samples were carried out at elevated temperatures of 623, 723 and 823 K using a reciprocating friction machine according to the scheme: “ball (ZrO2 with a diameter of 6.5) – flat sample” at a load of 20 N, a double stroke frequency of 5 Hz with a stroke length of 3 mm with a cycle time of 30 minutes. The microhardness of the coating was 500 HV0.1, which is 2.5 times higher than that of the substrate (200 HV0.1), due to solid solution hardening, fine crystalline structure and dislocation hardening. The type of wear of H13 steel can be attributed to abrasive, adhesive, fatigue and oxidative one, while the mechanism of wear of the WEC coating was abrasive and oxidative wear. Compared to H13 steel, the degree of coating wear was reduced by 59.20%, 70.79% and 78.20% at test temperatures of 623, 723 and 823 K, respectively.
An ASTM A‑36 carbon steel sheet (0.12%C) with a thickness of 6.35 mm was chosen as the base [12]. AISI 431 (METCO 42C) martensitic stainless steel powder obtained by gas spraying, with particle sizes of 69–101 microns was used for laser cladding. The treatment was performed with a disk laser (TruDisk 6002, Trumpf Inc.) at beam power of 1400 and 1600 W and travel speeds of 9, 14 and 16 mm/s, with a spot of 2.4 mm. A high-precision KUKA KR 60 robot was used to move the optical head. A feeder (GTV PF21) was used to supply the filler metal. A dendritic columnar structure was determined in the cladding tracks, which structure consisted of martensite in the form of dendrites and ferrite in the inter-dendritic zones. The average hardness values in the deposited tracks were 522 ± 4 HV0.5. In the zone of thermal influence, the hardness values were higher than in the substrate.
The purpose of this work is to determine the geometric parameters of the tracks cladded with 20X13 powder, microhardness, and wear resistance of the coating compared with the original 20X13 steel.
Equipment and research methods
To conduct experiments on broadband laser powder cladding, an automated technological complex based on a semiconductor technological laser PLD‑6 manufactured by INJECT RME LLC with a power of 6 kW was used. The cladding was carried out in an argon medium at a laser radiation power of 5.6 kW, a beam scanning speed of 3 mm/s with a powder feed rate of 35 g/min. Rectangular steel samples of 20X13 with dimensions of 40×80×20 mm were chosen as the base material. The cladded samples were cut perpendicular to the track on a 10 mm thick POLYLAB P55 cutting machine for the manufacture of polished sections. The polished sections were made according to a standard procedure using a P12 grinding and polishing machine. The thickness and width of the cladded tracks were determined using an AM413 ML digital microscope (UNICO, United Products and Instruments, USA). The microhardness of the deposited coating and the base material was determined on a PMT‑3 microhardness tester equipped with an MC‑8.3S digital camera at a load of 0.98 N. The structure of the cladding zone was determined using the MC‑1000 optical system.
Friction and wear tests were carried out according to the scheme: “rectangular sample (cladded sample, base)-end face of the annular counter sample of the sleeve (steel 45, HRC49–54)” at a pressure of 2 MPa on the samples when one drop per second of MGE‑10A hydraulic oil is applied to the friction zone.
Experiment tests results
Figure 1 shows a microsection of the sample with the measurement results of the 20X13 powder laser cladding track on 20X13 steel. The width of the cladded track zones was 22–23 mm with a surfacing height of 1.23–1.29 mm. There were no defects in the form of pores and cracks in the cladded tracks. The microhardness of the 20X13 powder cladding zones was 496–561 HV, followed by the 20X13 steel hardening zone with a microhardness of 501–575 HV, below the incomplete hardening zone of 245–485 HV, and then the base material zone of 190–216 HV. The graph of the microhardness change in the thickness of the deposited coating and the base material is shown in Fig. 2. The structure of the cladding zone (Fig. 3) consisted of differently oriented dendrites. The penetration depth of the 20X13 steel base material was 30–65 microns.
The results of the wear intensity tests of the samples are shown in Table No. 1. The average wear rate of 20X13 laser-coated powder samples was 0.199 · 10–9, which was 3.16 times lower than the wear rate of the base material of 20X13 steel. The wear rate of the counter sample made of hardened steel 45 was lower in the friction pair with the cladded sample compared to the base material. The average values of the friction rates for the cladded samples were 0.043, and the base material was 0.078.
Discussion of results
As a result of the work carried out, for the first time in domestic practice, a technology for laser broadband cladded of single tracks with a layer width of 22–23 mm at a height of 1.2–1.3 mm was developed using a slot nozzle for feeding powder material with a powder consumption of 36 g/min, which is 5–7 times higher than when cladding with a circular defocused beam with a diameter of 2–5 mm.
The new technology can find its application in restoring the rolling surfaces of railway wheel sets of passenger and especially freight wagons. In addition, this technology can be used for cladding of worn surfaces of large-sized dies, which for the most part have a hardness of 42–45 HRC.
Ploughshares, cultivator blades, disc harrows and other tillage tools can be another application of this technology.
Conclusion
The technology of broadband laser cladding of 20X13 steel with 20X13 powder has been developed with a surfacing zone width of 22–23 mm and a height of the deposited layers of 1.2–1.3 mm.
The average wear rate of the laser-surfaced samples was 3.16 times lower than the wear rate of the base material of the 20X13 steel. The wear rate of the counter sample made of hardened steel 45 was lower in the friction pair with the cladded sample compared to the base material. The average values of the friction rates for the cladded samples were 0.043, and the base material was 0.078. The performance of broadband laser cladding is 5–7 times higher than surfacing with a defocused laser beam with a diameter of 2–5 mm.
AUTHORS
Vladimir Pavlovich Birukov – Leading Researcher, Candidate of Technical Sciences, Mechanical Engineering Research Institute of the RAS (IMASH RAS), Moscow, Russia; e-mail: laser-52@yandex.ru
ORCID: 0000-0001-9278-6925
Andrey Nikolaevich Miryakha – Head of the Group, RME INJECT LLC, Saratov, Russia
ORCID: 0009-0009-7922-5520
Yaroslav Alekseevich Goryunov – Postgraduate Student, Mechanical Engineering Research Institute of the RAS (IMASH RAS), Moscow, Russia
V. P. Birukov 1, Ya. А. Gorunov 1, А. N. Miryakha 2
Mechanical Engineering Research Institute of the RAS (IMASH RAS), Moscow, Russia
RME INJECT LLC, Saratov, Russia
The paper considers the results of metallographic and tribotechnical tests of 20X13 steel samples and 20X13 steel samples with laser broadband cladding with 20X13 powder. The deposited layer had a dendritic differently oriented structure. The microhardness of the coating was 501–575 HV. It was found that the wear rate of the cladded coating is 3.16 times lower than that of the base material. The wear rate of the counter sample made of hardened steel 45 was lower in the friction pair with the cladded sample compared to the base material. The average friction factors for the cladded samples were 0.043, and for the base material was 0.078. The performance of broadband laser cladding is 5–7 times higher than when processing with a defocused beam.
Key words: laser cladding, microhardness, wear rate, friction factor
The article received on: January 13, 2025
The article accepted on February 03, 2025
Introduction
The development of new laser powder cladding technologies is an important task of modern mechanical engineering. The following are the research materials conducted by foreign and domestic authors in the field of developing laser cladding technologies. AISI 1020 steel (0.18–0.23%C) was chosen as the base material for [1] samples with dimensions 76.0 × 25.4 × 10.0 mm. Ni-Cr-B-Si powder with a particle size of 53–150 microns of the 1545–00 grade with a declared hardness of 490 HV30 and a density of 7.1 g/cm3 was used for laser cladding. The samples were cladded using an IPG PHOTONICS fiber laser source at radiation power of 1.05, 1.4, 1.75 kW, beam travel speeds of 5 (C1), 21.7 (C2), 30 (C3) mm/sec, a track overlap coefficient of 30%. The samples were tested for abrasive wear according to the ASTM G65 standard according to the scheme: “annular surface of an elastic circle – a flat sample (base material, coating)” with quartz sand being gravity-fed into the friction zone. The results of the abrasive wear tests showed that samples C1 had maximum abrasive resistance, followed by samples C2 and C3 in descending order of abrasive resistance. Transverse cracks were found on samples C2 and C3, which, according to the authors, could have been prevented by preheating the samples.
For the production of samples [2], 45 steel was chosen, which was widely used in the manufacture of hydraulic cylinders. A standard 316L grade metal powder with a particle size of 53–150 microns was used for laser cladding. The samples were processed using a disk laser (TruDisk 4002, Germany) with a wavelength of 1030 nm in an environment of protective gas, argon with a flow rate of 10 l/min at room temperature, a radiation power of 2600 W, a scanning speed of 10 mm/s and a 50% overlap coefficient of the cladding tracks. Tribotechnical tests were carried out according to the scheme: “a ball (Si3N4, 4 mm in diameter with a hardness of 78 HRC) is a flat sample) at a load of 5 N and a rotational speed of 100 min‑1 with a cycle duration of 30 min. Disc samples with a diameter of 40 mm and a thickness of 10 mm were produced for wear and corrosion resistance tests. The samples were heated in a salt bath at a temperature of 1050 °C for 1 hour in a heat treatment furnace followed by air cooling. The microhardness of the deposited coatings was 170–200 HV, and after heating in a salt bath it was 240–280 HV. The increased corrosion resistance of the deposited layer with 316L powder treated in a salt furnace was explained by an increase in the microhardness of the surface. The typical mechanism of destruction during corrosion wear was abrasive wear and plastic deformation, while the main mechanism of destruction under normal wear conditions was brittle fracture of microzones and abrasive wear. The corrosive environment accelerated the wear process by about 3 times compared to what happened without the corrosive effect.
For experiments [3] on laser cladding, 27SiMn steel samples with a diameter of 150 mm and a thickness of 60 mm were used. An iron-based alloy with Cr, Ni and Si additives (average hardness 51 HRC) with an average particle size of 38 microns of spherical shape was used as a cladding powder, which ensured its better fluidity. The samples were cladded using an RFL–C4000 laser installation (Raycus Fiber Laser, Wuhan, China) – with coaxial argon powder supply, which was also used to protect molten metal at a laser power of 2.7 kW and a track overlap of 80%. Tribotechnical tests were carried out on a multifunctional friction machine (CFT-I, Zhongkekaihua, Lanzhou, China) without lubricant according to the scheme: “ball (Si3N4, diameter 5 mm) – coated sample” at a normal load of 30 N, the rotation speed of 500 min–1, and the cycle time of 30 min. To determine the characteristics of the cladded coating, samples of two types were produced: A (the upper region of the cladded layer, the thickness of which was 1.1 mm) and B (the middle region of the lining layer, the thickness from the substrate after cutting was 0.55 mm). The cladded layer of sample A contained more metal compounds and carbide phases with fine grains, and the structure of sample B consisted mainly of elongated dendrites. The microhardness of sample B was higher than that of sample A. The abrasion resistance of sample B was about 2.7 times higher than that of sample A. The mechanism of wear of sample A consisted in adhesive and abrasive wear, and for sample B in abrasive wear.
An SS316L stainless steel plate with dimensions of 100×20×60 mm was used as a substrate [4].
WC-NiCrMo powder with a spherical particle size of 30–53 microns was used for laser cladding. A diode laser system with flexible fiber LDF400–2000 (1600 W) with a round spot with a diameter of 4 mm and a diode laser system FL-DLight‑3000-976 (2400 W) with a rectangular spot of 12×2 mm were used for cladding. The laser scanning rate was 420 mm/min for the first and 180 mm/min for the second samples, with a powder consumption of 10 g/min for both coatings. 10 tracks were cladded with an overlap factor of 50%. Metallographic tests have established that the width and height of the cladded rollers for a round and rectangular spot were 5 and 0.86 mm, 9.2 and 1.27 mm, respectively. The maximum penetration depth of the substrate when surfaced with a circular beam was 0.62 mm, which is 6 times greater than when treated with a rectangular spot. The hardness for the first and second coatings also differed and amounted to 50 and 60 HRC, respectively. The wear resistance of the coatings was evaluated during wear tests according to the scheme: “ball (Si3N4, 1300 HV0.2) – disc (coated sample) without lubricant at a disk rotation speed of 350 min–1, a normal load of 400 g, and a cycle time of 2 hours. After the experiment was completed, a circular trace of a friction track with a diameter of 6 mm was formed on the surface of the sample. The wear resistance of the coating obtained by cladding with a rectangular spot was higher than after cladding with a circular beam.
Samples [5] made of stainless steel 0Cr17Ni12Mo2 with dimensions of 300×120×10 mm were used for laser cladding. Ni60 nickel-based powder (24–48 microns) and WC powder (16–48 microns) of 5 (1), 7.5 (2) and 10 (3) %wt were used as the charge material. Laser processing was performed on a Raycus RFL–C1000 installation equipped with a manipulator with six degrees of freedom, at laser power 800 W, a spot diameter of 1.8 mm and a scanning speed of 8 mm/s with a powder feed rate of 6.5 g/min, and argon was used to protect the zone from oxidation.
Friction and wear tests were carried out on an MPX‑3 G friction machine at temperatures of 20, 300, and 600 Celsius degrees according to the scheme: “ball (silicon nitride with a diameter of 6.35 mm) - disk” at a load of 50 N, a disk rotation speed of 400 min−1, and a cycle time of 50 minutes. In the field of laser surfacing, solid phases WC, W2C, Mn23C6, Fe3C, and Cr3Ni2SiC were observed, and the microhardness increased with increasing WC content. The friction rates increased with an increase in temperature to 300 Celsius degrees, and their decrease was observed at 600 Celsius degrees. The minimum wear rate was for the cladded coatings (1), and for coatings (2) it increased sharply, and for samples with coatings (3) it was lower than for coatings (2). Increase in temperature led to increase in the wear rate of the samples.
Rectangular samples [6] of W10V5Co4 steel were coated with W10V5Co4 powder and Si: 2%wt and B: 4%wt additives with the help of a diode laser with a radiation power of 1800 W, a 4×4 mm laser spot size, a scanning speed of 8 mm/s, and a 40% track overlap coefficient. Tests for dry sliding friction during reciprocating motion were performed using an Rtec universal tribometer (MFT‑5000) according to the scheme: “flat ladded sample-ball (aluminum oxide)” at a load of 10 N and a double stroke frequency of 200 min‑1 in accordance with the ASTM G132-96 standard. W10V5Co4Si2B4 coatings with a hardness of 908 HV0.2 had the highest wear resistance. The wear rate of these coatings was 1.5×10–8 mm3/(N·mm), which is 2.8 times lower than that of the original alloy steel W10V5Co4.
MSS 410 powders and titanium carbide TiC additives (0, 5%, 10%, 15%) were laser-cladded onto rectangular samples [7] made of Q235 steel. Before cladding, to obtain a uniform distribution, both powders had been mixed using a QM‑3SP04L ball mill with a rotation speed of 120 min‑1 for 2 hours, then dried in an oven at 100 Celsius degrees for 2 hours. TiC powders contained most of the small particles of 7 microns in size and a small number of irregularly shaped particles of 20–50 microns. Laser surfacing was performed at a radiation power of 480 W, a spot diameter of 1.2 mm, a travel speed of 480 mm/min, an energy density of 100 J/mm3, with a 50% cladding track overlap and a powder feed rate of 6.5 g/min. Tribotechnical experiments on coated samples were carried out on a friction machine according to the “ball-disc” scheme at room temperature. A ball made of Si3N4 (1700 HV, with a surface roughness of 0.2 microns) with a diameter of 5 mm was chosen as a counter sample. The tests were carried out at a rotational speed of 840 min‑1, a friction radius of 3 mm, a load of 10 N and a cycle time of 30 min. It was found that the microhardness and wear resistance of the coatings increased with an increase in the titanium carbide content to 10%, and microcracks were found at 15% of the TiC content, which reduced the wear resistance of the samples.
Samples [8] of AISI 1045 steel were cladded with Fe–Cr–N powder with a laser beam at a radiation power of 3 kW and a displacement speed of 5.1 mm/s. Corrosion resistance was assessed by the method of potentiodynamic polarization in a 10% NaCl solution prepared from distilled water at room temperature. The coating was resistant to corrosion, and the polarization resistance was increased six times compared to steel 1045.
Stainless steel powders 316L, 410 and 420 were used as materials for cladding of rollers [9] from wheel steel, while the counter sample rollers were made of rail steel. Laser cladding was performed at a laser beam power of 500 W, a spot diameter of 2.2 mm, a scanning speed of 10 mm/s for 316L stainless steel and 8 mm/s for 410 and 420 steel, a layer thickness of 2.2 mm, a powder feed rate of 1.2 g/min, and a protective gas flow rate of 12 l/min. To study roller wear during rolling, a “roller-roller” test scheme was applied. The rotation speed of the counter sample roller made of rail steel was 500 min‑1, the contact pressure according to Hertz was 1100 MPa, the slip coefficient was 0.75%, and the test duration was 100,000 cycles. All three coatings had low wear compared to the non-cladded rollers made from the original steel. As the hardness of the deposited materials increased, the wear rate decreased. Small surface cracks were found on the surface of individual laser-cladded samples. Deep cracks were found at the boundary between the coating and the substrate. Cracks appeared where the maximum shear stress was formed below the surface, and then they spread along the boundary between the coating and the substrate.
The use of laser cladding [10] in the repair of mining equipment is an urgent task. For laser cladding, samples of 38XMA (0.38%C) and 42XFA (0.42%C) steel and 38XMA, 42XFA and Inconel 718 powders were selected. Laser cladding was performed using the Optomec LENS 450 system, which included a laser and a powder supply system. Cylindrical rods made of 38XMA and 42XFA steel (30 mm long and 10 mm in diameter) were selected as test samples. The tribological properties of the coatings were determined with dry sliding friction according to the scheme: “pin (cladded sample or steel sample) -disc (ZrO2)” at a sliding speed of 0.52 m/s and a load of 160 N on a friction path of 300 m. Inconel 718 alloy had better mechanical and tribological properties compared to other deposited powders. The wear resistance of the cladded coatings with 38XMA and 42XFA powders was 1.7 times lower than that of the Inconel 718 powder-coated samples.
For the production of samples [11], H13 steel with dimensions of 60×50×5 mm was used. A CO2 laser with transverse pumping of gases DL2000, China, was used as equipment for laser cladding at a radiation power of 1300 W, a displacement speed of 240 mm/min, a beam diameter of 3 mm, with a track overlap of 30%. High-entropy FeCoCrNiAl alloy (WEC) powder with a particle size of 50–80 microns was used for the coating. Friction and wear tests of H13 steel samples and WEC coated samples were carried out at elevated temperatures of 623, 723 and 823 K using a reciprocating friction machine according to the scheme: “ball (ZrO2 with a diameter of 6.5) – flat sample” at a load of 20 N, a double stroke frequency of 5 Hz with a stroke length of 3 mm with a cycle time of 30 minutes. The microhardness of the coating was 500 HV0.1, which is 2.5 times higher than that of the substrate (200 HV0.1), due to solid solution hardening, fine crystalline structure and dislocation hardening. The type of wear of H13 steel can be attributed to abrasive, adhesive, fatigue and oxidative one, while the mechanism of wear of the WEC coating was abrasive and oxidative wear. Compared to H13 steel, the degree of coating wear was reduced by 59.20%, 70.79% and 78.20% at test temperatures of 623, 723 and 823 K, respectively.
An ASTM A‑36 carbon steel sheet (0.12%C) with a thickness of 6.35 mm was chosen as the base [12]. AISI 431 (METCO 42C) martensitic stainless steel powder obtained by gas spraying, with particle sizes of 69–101 microns was used for laser cladding. The treatment was performed with a disk laser (TruDisk 6002, Trumpf Inc.) at beam power of 1400 and 1600 W and travel speeds of 9, 14 and 16 mm/s, with a spot of 2.4 mm. A high-precision KUKA KR 60 robot was used to move the optical head. A feeder (GTV PF21) was used to supply the filler metal. A dendritic columnar structure was determined in the cladding tracks, which structure consisted of martensite in the form of dendrites and ferrite in the inter-dendritic zones. The average hardness values in the deposited tracks were 522 ± 4 HV0.5. In the zone of thermal influence, the hardness values were higher than in the substrate.
The purpose of this work is to determine the geometric parameters of the tracks cladded with 20X13 powder, microhardness, and wear resistance of the coating compared with the original 20X13 steel.
Equipment and research methods
To conduct experiments on broadband laser powder cladding, an automated technological complex based on a semiconductor technological laser PLD‑6 manufactured by INJECT RME LLC with a power of 6 kW was used. The cladding was carried out in an argon medium at a laser radiation power of 5.6 kW, a beam scanning speed of 3 mm/s with a powder feed rate of 35 g/min. Rectangular steel samples of 20X13 with dimensions of 40×80×20 mm were chosen as the base material. The cladded samples were cut perpendicular to the track on a 10 mm thick POLYLAB P55 cutting machine for the manufacture of polished sections. The polished sections were made according to a standard procedure using a P12 grinding and polishing machine. The thickness and width of the cladded tracks were determined using an AM413 ML digital microscope (UNICO, United Products and Instruments, USA). The microhardness of the deposited coating and the base material was determined on a PMT‑3 microhardness tester equipped with an MC‑8.3S digital camera at a load of 0.98 N. The structure of the cladding zone was determined using the MC‑1000 optical system.
Friction and wear tests were carried out according to the scheme: “rectangular sample (cladded sample, base)-end face of the annular counter sample of the sleeve (steel 45, HRC49–54)” at a pressure of 2 MPa on the samples when one drop per second of MGE‑10A hydraulic oil is applied to the friction zone.
Experiment tests results
Figure 1 shows a microsection of the sample with the measurement results of the 20X13 powder laser cladding track on 20X13 steel. The width of the cladded track zones was 22–23 mm with a surfacing height of 1.23–1.29 mm. There were no defects in the form of pores and cracks in the cladded tracks. The microhardness of the 20X13 powder cladding zones was 496–561 HV, followed by the 20X13 steel hardening zone with a microhardness of 501–575 HV, below the incomplete hardening zone of 245–485 HV, and then the base material zone of 190–216 HV. The graph of the microhardness change in the thickness of the deposited coating and the base material is shown in Fig. 2. The structure of the cladding zone (Fig. 3) consisted of differently oriented dendrites. The penetration depth of the 20X13 steel base material was 30–65 microns.
The results of the wear intensity tests of the samples are shown in Table No. 1. The average wear rate of 20X13 laser-coated powder samples was 0.199 · 10–9, which was 3.16 times lower than the wear rate of the base material of 20X13 steel. The wear rate of the counter sample made of hardened steel 45 was lower in the friction pair with the cladded sample compared to the base material. The average values of the friction rates for the cladded samples were 0.043, and the base material was 0.078.
Discussion of results
As a result of the work carried out, for the first time in domestic practice, a technology for laser broadband cladded of single tracks with a layer width of 22–23 mm at a height of 1.2–1.3 mm was developed using a slot nozzle for feeding powder material with a powder consumption of 36 g/min, which is 5–7 times higher than when cladding with a circular defocused beam with a diameter of 2–5 mm.
The new technology can find its application in restoring the rolling surfaces of railway wheel sets of passenger and especially freight wagons. In addition, this technology can be used for cladding of worn surfaces of large-sized dies, which for the most part have a hardness of 42–45 HRC.
Ploughshares, cultivator blades, disc harrows and other tillage tools can be another application of this technology.
Conclusion
The technology of broadband laser cladding of 20X13 steel with 20X13 powder has been developed with a surfacing zone width of 22–23 mm and a height of the deposited layers of 1.2–1.3 mm.
The average wear rate of the laser-surfaced samples was 3.16 times lower than the wear rate of the base material of the 20X13 steel. The wear rate of the counter sample made of hardened steel 45 was lower in the friction pair with the cladded sample compared to the base material. The average values of the friction rates for the cladded samples were 0.043, and the base material was 0.078. The performance of broadband laser cladding is 5–7 times higher than surfacing with a defocused laser beam with a diameter of 2–5 mm.
AUTHORS
Vladimir Pavlovich Birukov – Leading Researcher, Candidate of Technical Sciences, Mechanical Engineering Research Institute of the RAS (IMASH RAS), Moscow, Russia; e-mail: laser-52@yandex.ru
ORCID: 0000-0001-9278-6925
Andrey Nikolaevich Miryakha – Head of the Group, RME INJECT LLC, Saratov, Russia
ORCID: 0009-0009-7922-5520
Yaroslav Alekseevich Goryunov – Postgraduate Student, Mechanical Engineering Research Institute of the RAS (IMASH RAS), Moscow, Russia
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