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At the processing facility, equipped with a fiber laser, produced by LLC NTO "IRE-Polus", is worked-out a laser cladding process. Powder materials based on nickel and welding modes, allowing to increase fatigue resistance are defined.
Теги: corrosion-resistant cover laser cladding surface hardening wear-resistant cover износостойкие покрытия коррозионно-стойкие покрытия лазерная наплавка поверхностное упрочнение
The development of advanced methods of modifying the surfaces of highly loaded parts of working units and mechanisms using concentrated energy sources due to the possibility of formation of surface layers , which have significant advantages as compared to layers produced by conventional methods of surface hardening, spraying and surfacing [1–4] .
In modern engineering production the most important task is to increase the service life of parts and assemblies manufactured friction and introduced earlier in the operation of vehicles. Details such as electrical machinery shafts, rotors for gas pumping stations, crankshafts out of service due to wear of the seating surfaces. Currently, the park operated equipment and machinery has wear similar friction units within 60 – 80 %. Recovery technology work surfaces can extend performance machines. These technologies include the restoration of working part dimensions laser powder cladding. Replacing one rotor gas-pumping station averages 15 million rubles, and the cost of restoring cervical rotor laser cladding is within 100 – 200 thousand rubles, depending on the size of the rotor, which indicates the high efficiency of the process of recovery.
Laser cladding is applied in the case where the heat affected zone should be minimized. Using laser cladding, depending on the operational requirements may be applied to the surface coating composed wear, corrosion, and other components that can satisfy the increasing demands for high wear resistance and toughness in a broad range of operating conditions, including dynamic loading.
In the process of laser cladding with coaxial powder feeding a carrier gas stream forms a weld filler metal, which is melted under the influence of powerful laser radiation. On the surface of a molten pool of the substrate occurs, which after hardening forms a single weld bead [3–6]. Dense cover a large area is obtained by imposing single rollers with overlapping 30 – 50 % of the diameter of the laser beam.
The objectives of the work was to determine the influence of the composition of the powder material and mode of laser cladding on the strength of adhesion of the coating to the base material, increased wear and fatigue resistance of the samples.
Performing experiments on the basis of nickel powder produced at the processing facility HUFFMAN HC- 205 equipped with a fiber laser LS- 3, 5 power 3500 W manufactured by LLC NTO " IRE- Polus" [3,6] . For testing laser cladding process used powder mass flow – 1.5–6 g / min; argon pressure – 2 bar . stream of argon – 3 l / min; powder having a particle size of 40 – 160 µm. Surfacing on steel samples 35 and 38HN3MA produced when radiation power 500 – 1000 W, the velocity of the 5 – 25 mm/s. The microstructure of deposited coatings was investigated using an optical microscope metallographic Neophot – 30 , manufactured by Carl Zeiss JENA increasing to 500 -fold. The microstructure shown in Fig.1.
Microhardness of the samples was measured by Vickers and was deposited layers for 4250 – 5200 MPa.
Test samples for adhesion strength of coating to the substrate were carried out in accordance with the RM250 -87 "Determination of adhesive strength of thermal coating to the base metal. Guidelines "and the methodological recommendations LLC NTO" IRE – Polus."
The technique consists in that a cylindrical specimen of the test material, weld it in the form of an annular girdle layer is extruded through the die . While under the influence of shear stresses occur slice of the deposited layer and the shear stress characterizes the adhesion strength of the deposited layer to the substrate .
Sample was made of the test of the base metal in the form of a cylinder of diameter 24 mm and length 25 mm. The thickness of the deposited layer was 0.8 – 1.3 mm. The width of the weld girdle 10 – 0.5 mm, and symmetrically relative to the bore after the end of the sample 4-0,05 mm. As a result of the tests, the values of adhesion strength of coatings within 295 – 524 MPa, depending on the mode of treatment and composition of the particulate material. For comparison, adhesion strength of the deposition of coatings at high speed does not exceed 80 MPa. Furthermore, the slice identified by the shear stresses of the base material, which amounted to 330 MPa.
Abrasion tests were the following combinations of materials. Wear-resistant coating based on samples of Ni – coated rollers from medium alloyed steel 38ХН3МА (ГОСТ 4543-71 ) in a normalized state, having the following composition: 0.33 – 0.4 % C , 1,2 – 1,5% Cr, 3 – 3,5% Ni, 0,35 – 0,45 % Mo. Investigated four types of laser resurfacing: C.1.; C.2; C.3; and C.4. Also tested samples clips uncoated. Samples – pads made from quality carbon steel 35 in the normalized condition (ГОСТ 1050-88). On work surfaces specimens pad applied babbitt coating. Coating material samples – Pad – Babbit B83 from tin (ГОСТ 1320-74), having a composition of 83 % Sn, 11 % Sb, 6 % Cu. Tested three pairs of each combination of materials. Samples were pre- run-in for 30 minutes by supplying to a zone of friction of the lubricating oil TP – 22C under a load of 125 N. burnishing achieved even distribution of wear on the friction surfaces of both pairs of samples. Further tests were carried out for 2 hours at a pressure of 2.5 MPa in terms of continuous supply of lubricant the friction zone. Results of wear testing are presented in Table.
The tests carried out on the friction machine MI – 1 deposited coating against friction with babbitt B83 showed an improvement in wear resistance 2 – 4 times compared with steels and 38ХН3МА 35 [6, 7]. To assess the effect of the deposited layer on the material to scoring tests were carried out on the machine friction MTU- 01 scheme of mechanical friction. Samples were pre- run-in for 30 minutes at a feed zone of the working oil and the friction load of 150 N at a spindle rotation speed of 200 min-1. Burnishing equal distribution of wear on the friction surfaces of both samples couples. Further tests were carried out to a step change in the speed range of 200 – 900 min-1 in 100 min-1 under continuous supply of oil to the friction zone. During the test, a continuous record of the friction torque in contact. Bullies in the friction pair fixed by an abrupt increase in the frictional torque. As a result of the friction test machine MTU 01 at three samples is set for each type of coating that seizure uncoated samples occurs at a rotational speed of 500 min-1, and the samples deposited on the nickel-based powder with speeds of 600 – 900 min -1.
To determine the optimal surface hardening techniques to improve the performance properties of coatings by fatigue, comparative tests were conducted on the fatigue. Tests were carried out at a bend with rotation in a symmetric loading cycle. Base test was taken as 2.106 cycles. Registration number of cycles carried out with a counter and concomitant fixation test time. With the destruction of the sample occurs automatically stop the machine.
Investigated samples smooth 7.5 mm diameter, made of steel 35 and 38HN3MA. Type specimens for fatigue tests is shown in Fig.2. Parameters fatigue curves were determined using regression analysis. Fatigue curve equation is written as
.
Determination of parameters of fatigue curves and their construction was carried out taking into account the sample without destroying the base to the highest test 2.106 cycles. The results of fatigue tests of specimens of steel 35 deposited powder П 2 shown in Fig.3. [8]. Points with arrows indicate that the samples did not break up the highest base tests. For a given material deposition techniques and conducted tests show a decrease in fatigue resistance fatigue performance after laser cladding (2 and 3) compared to the fatigue curve of the original (1).
Machining and polishing the deposited layer significantly improves the fatigue properties of deposited samples, as was noted earlier in [9]. To improve the fatigue resistance of the samples was carried out optimization technology of laser cladding powder materials. Influence of deposition technologies investigated on samples from four 38HN3MA steel powders based on nickel , characterized by its parameters ( power of the radiation width of the track surfacing unit, movement speed of the beam), build-up zone on the width of the sample was within 30 – 35 mm. The main optimization criterion was the absence of cracks in the deposited layers. After surfacing samples were machined and polished. The resulting fatigue curves shown in Fig. 4.
Analysis of fatigue curves shows that modes 2 and 5, indicated in Fig.4. Exhortation increase fatigue resistance , especially at high loads. At the same time in [10] found that with increasing sample size, made of 45 steel in the initial state and after laser surfacing with a diameter of 7.5 mm to a diameter of 17.5 mm negative impact on the performance of laser cladding fatigue resistance decreases. Therefore, the use of laser cladding on parts having considerable weight and dimensions, such as rotors of electrical machines, gas compressor stations , cam and crankshafts, dramatically increases their fatigue strength compared to samples used for fatigue tests .
Studies suggest that the developed technology of laser cladding increases the wear resistance of the friction pair in 2 – 4 times and can be used to restore the seating surfaces of the rotors of gas pumping units, electrical machinery shafts, crankshafts necks, etc. In addition, for the surfacing of new parts with to increase the reliability and longevity of their work.
Selection of optimal cladding technology can improve the fatigue resistance characteristics. Application after laser cladding subsequent machining characteristics enhances fatigue resistance weld samples.Defined powder materials based on nickel and surfacing modes allow to increase fatigue strength. Adhesion strength of the deposited coating strength of the base material above the shear from which manufactured the machines, under optimal cladding.
This work was financially supported by LLC NTO "IRE – Polus."
In modern engineering production the most important task is to increase the service life of parts and assemblies manufactured friction and introduced earlier in the operation of vehicles. Details such as electrical machinery shafts, rotors for gas pumping stations, crankshafts out of service due to wear of the seating surfaces. Currently, the park operated equipment and machinery has wear similar friction units within 60 – 80 %. Recovery technology work surfaces can extend performance machines. These technologies include the restoration of working part dimensions laser powder cladding. Replacing one rotor gas-pumping station averages 15 million rubles, and the cost of restoring cervical rotor laser cladding is within 100 – 200 thousand rubles, depending on the size of the rotor, which indicates the high efficiency of the process of recovery.
Laser cladding is applied in the case where the heat affected zone should be minimized. Using laser cladding, depending on the operational requirements may be applied to the surface coating composed wear, corrosion, and other components that can satisfy the increasing demands for high wear resistance and toughness in a broad range of operating conditions, including dynamic loading.
In the process of laser cladding with coaxial powder feeding a carrier gas stream forms a weld filler metal, which is melted under the influence of powerful laser radiation. On the surface of a molten pool of the substrate occurs, which after hardening forms a single weld bead [3–6]. Dense cover a large area is obtained by imposing single rollers with overlapping 30 – 50 % of the diameter of the laser beam.
The objectives of the work was to determine the influence of the composition of the powder material and mode of laser cladding on the strength of adhesion of the coating to the base material, increased wear and fatigue resistance of the samples.
Performing experiments on the basis of nickel powder produced at the processing facility HUFFMAN HC- 205 equipped with a fiber laser LS- 3, 5 power 3500 W manufactured by LLC NTO " IRE- Polus" [3,6] . For testing laser cladding process used powder mass flow – 1.5–6 g / min; argon pressure – 2 bar . stream of argon – 3 l / min; powder having a particle size of 40 – 160 µm. Surfacing on steel samples 35 and 38HN3MA produced when radiation power 500 – 1000 W, the velocity of the 5 – 25 mm/s. The microstructure of deposited coatings was investigated using an optical microscope metallographic Neophot – 30 , manufactured by Carl Zeiss JENA increasing to 500 -fold. The microstructure shown in Fig.1.
Microhardness of the samples was measured by Vickers and was deposited layers for 4250 – 5200 MPa.
Test samples for adhesion strength of coating to the substrate were carried out in accordance with the RM250 -87 "Determination of adhesive strength of thermal coating to the base metal. Guidelines "and the methodological recommendations LLC NTO" IRE – Polus."
The technique consists in that a cylindrical specimen of the test material, weld it in the form of an annular girdle layer is extruded through the die . While under the influence of shear stresses occur slice of the deposited layer and the shear stress characterizes the adhesion strength of the deposited layer to the substrate .
Sample was made of the test of the base metal in the form of a cylinder of diameter 24 mm and length 25 mm. The thickness of the deposited layer was 0.8 – 1.3 mm. The width of the weld girdle 10 – 0.5 mm, and symmetrically relative to the bore after the end of the sample 4-0,05 mm. As a result of the tests, the values of adhesion strength of coatings within 295 – 524 MPa, depending on the mode of treatment and composition of the particulate material. For comparison, adhesion strength of the deposition of coatings at high speed does not exceed 80 MPa. Furthermore, the slice identified by the shear stresses of the base material, which amounted to 330 MPa.
Abrasion tests were the following combinations of materials. Wear-resistant coating based on samples of Ni – coated rollers from medium alloyed steel 38ХН3МА (ГОСТ 4543-71 ) in a normalized state, having the following composition: 0.33 – 0.4 % C , 1,2 – 1,5% Cr, 3 – 3,5% Ni, 0,35 – 0,45 % Mo. Investigated four types of laser resurfacing: C.1.; C.2; C.3; and C.4. Also tested samples clips uncoated. Samples – pads made from quality carbon steel 35 in the normalized condition (ГОСТ 1050-88). On work surfaces specimens pad applied babbitt coating. Coating material samples – Pad – Babbit B83 from tin (ГОСТ 1320-74), having a composition of 83 % Sn, 11 % Sb, 6 % Cu. Tested three pairs of each combination of materials. Samples were pre- run-in for 30 minutes by supplying to a zone of friction of the lubricating oil TP – 22C under a load of 125 N. burnishing achieved even distribution of wear on the friction surfaces of both pairs of samples. Further tests were carried out for 2 hours at a pressure of 2.5 MPa in terms of continuous supply of lubricant the friction zone. Results of wear testing are presented in Table.
The tests carried out on the friction machine MI – 1 deposited coating against friction with babbitt B83 showed an improvement in wear resistance 2 – 4 times compared with steels and 38ХН3МА 35 [6, 7]. To assess the effect of the deposited layer on the material to scoring tests were carried out on the machine friction MTU- 01 scheme of mechanical friction. Samples were pre- run-in for 30 minutes at a feed zone of the working oil and the friction load of 150 N at a spindle rotation speed of 200 min-1. Burnishing equal distribution of wear on the friction surfaces of both samples couples. Further tests were carried out to a step change in the speed range of 200 – 900 min-1 in 100 min-1 under continuous supply of oil to the friction zone. During the test, a continuous record of the friction torque in contact. Bullies in the friction pair fixed by an abrupt increase in the frictional torque. As a result of the friction test machine MTU 01 at three samples is set for each type of coating that seizure uncoated samples occurs at a rotational speed of 500 min-1, and the samples deposited on the nickel-based powder with speeds of 600 – 900 min -1.
To determine the optimal surface hardening techniques to improve the performance properties of coatings by fatigue, comparative tests were conducted on the fatigue. Tests were carried out at a bend with rotation in a symmetric loading cycle. Base test was taken as 2.106 cycles. Registration number of cycles carried out with a counter and concomitant fixation test time. With the destruction of the sample occurs automatically stop the machine.
Investigated samples smooth 7.5 mm diameter, made of steel 35 and 38HN3MA. Type specimens for fatigue tests is shown in Fig.2. Parameters fatigue curves were determined using regression analysis. Fatigue curve equation is written as
.
Determination of parameters of fatigue curves and their construction was carried out taking into account the sample without destroying the base to the highest test 2.106 cycles. The results of fatigue tests of specimens of steel 35 deposited powder П 2 shown in Fig.3. [8]. Points with arrows indicate that the samples did not break up the highest base tests. For a given material deposition techniques and conducted tests show a decrease in fatigue resistance fatigue performance after laser cladding (2 and 3) compared to the fatigue curve of the original (1).
Machining and polishing the deposited layer significantly improves the fatigue properties of deposited samples, as was noted earlier in [9]. To improve the fatigue resistance of the samples was carried out optimization technology of laser cladding powder materials. Influence of deposition technologies investigated on samples from four 38HN3MA steel powders based on nickel , characterized by its parameters ( power of the radiation width of the track surfacing unit, movement speed of the beam), build-up zone on the width of the sample was within 30 – 35 mm. The main optimization criterion was the absence of cracks in the deposited layers. After surfacing samples were machined and polished. The resulting fatigue curves shown in Fig. 4.
Analysis of fatigue curves shows that modes 2 and 5, indicated in Fig.4. Exhortation increase fatigue resistance , especially at high loads. At the same time in [10] found that with increasing sample size, made of 45 steel in the initial state and after laser surfacing with a diameter of 7.5 mm to a diameter of 17.5 mm negative impact on the performance of laser cladding fatigue resistance decreases. Therefore, the use of laser cladding on parts having considerable weight and dimensions, such as rotors of electrical machines, gas compressor stations , cam and crankshafts, dramatically increases their fatigue strength compared to samples used for fatigue tests .
Studies suggest that the developed technology of laser cladding increases the wear resistance of the friction pair in 2 – 4 times and can be used to restore the seating surfaces of the rotors of gas pumping units, electrical machinery shafts, crankshafts necks, etc. In addition, for the surfacing of new parts with to increase the reliability and longevity of their work.
Selection of optimal cladding technology can improve the fatigue resistance characteristics. Application after laser cladding subsequent machining characteristics enhances fatigue resistance weld samples.Defined powder materials based on nickel and surfacing modes allow to increase fatigue strength. Adhesion strength of the deposited coating strength of the base material above the shear from which manufactured the machines, under optimal cladding.
This work was financially supported by LLC NTO "IRE – Polus."
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