CN110965058A

CN110965058A - NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating

Info

Publication number: CN110965058A
Application number: CN201811143980.5A
Authority: CN
Inventors: 王洪伟
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-09-29
Filing date: 2018-09-29
Publication date: 2020-04-07

Abstract

A self-lubricating antiwear NiCr/Cr3C2/WS2 coating is prepared from NiCr/Cr3C2 and NiCr/Cr3C2-30% WS on 0Crl8Ni9 stainless steel substrate by laser cladding technique₂The cladding coating of the wear-resistant self-lubricating coating added with WS2 mainly comprises Cr₇C₃A (Cr, W) C carbide reinforcing phase, gamma- (Fe, Ni)/Cr₇C₃Eutectic toughening phase, WS₂And a CrS lubricating phase. Both coatings decrease in friction factor and increase in wear rate with increasing temperature. At room temperature and 300 deg.C, WS is added₂The coating has better antifriction and wear resistance due to the action of the lubricating phase. At 600 c, the wear rate of both coatings increases significantly due to the reduced strength of the carbide hard phase in the coating.

Description

NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating

Technical Field

The invention relates to a surface coating material, in particular to a NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating.

Background

In the advanced technical fields of aviation, aerospace, nuclear energy and the like, a large number of friction kinematic pair parts which operate under severe working condition environments such as high vacuum degree, high temperature, high speed, heavy load and the like exist, such as high-temperature heat insulation engine bearings, piston rings, cylinder sleeves, nuclear valves, turbine blades and the like, common lubricating grease cannot fully meet the use requirements, and a solid self-lubricating coating is one of effective ways for solving the problems. At present, laser cladding is one of effective means for preparing a solid self-lubricating coating, and due to the high energy density of the technology, an additive material and a shallow surface layer of a base material are quickly melted and solidified to form a high-strength coating which is compact in structure, fine in crystal grains and metallurgically bonded with a matrix.

Selecting WS₂As solid lubricants, WS₂The density is higher and is 7.59/cm³And has good wettability with the metal matrix due to the properties of the near metal phase. WS₂The lubricating transfer film is in a hexagonal crystal system and a layered structure, and Van der Waals force acts between layers, so that the shearing strength is low, the lubricating transfer film is easily formed on a contact surface under the action of friction force, the friction factor of a friction pair is reduced, and the abrasion is reduced. NiCr-Cr₃C₂Is a common metal ceramic powder and has the functions ofNiCr alloy and Cr₃C₂The powder has the advantages of excellent comprehensive performances of wear resistance, corrosion resistance, oxidation resistance and the like at high temperature. Austenitic stainless steel is widely used for manufacturing mechanical parts and components in industries such as nitric acid, organic acid, salt, alkali and the like due to good mechanical property and chemical stability. The 0Crl8Ni9 stainless steel is widely used in the fields of building, metallurgy, chemical industry, medical treatment and the like due to the excellent high-temperature oxidation resistance and corrosion resistance. But the high-temperature hardness and the wear resistance are low, so that the application of the high-temperature friction pair part is limited.

Disclosure of Invention

The invention aims to improve the wear resistance of a stainless steel composite material, and designs a NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating is prepared from the following raw materials: a hot rolled 0Crl8Ni9 austenitic stainless steel was selected as the base material, having a hardness of about 200HV, and cut into 50mm by 40mm by 8mm samples. And (3) polishing the surface of the substrate by using sand paper, and cleaning the substrate by using an ethanol solution. The cladding material is Ni80Cr20-Cr₃C₂Cermet powder with NiCr alloy in 30 wt% and solid lubricant WS₂The amount of (B) added is 30%.

The preparation method of the NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating comprises the following steps: weighing by an electronic balance, mixing, and ball milling for 2h in a ball mill (QM-SP 04). The mixed powder was then preplaced on a 0Crl8Ni9 matrix using a methylcellulose binder to a thickness of about 1.5 mm. And finally, placing the mixture in a drying box, heating to 80 ℃, and keeping the temperature and drying for 2 h. GS-TFI-10kW type high-power transverse flow CO is adopted by laser cladding equipment₂The laser and the cladding technological parameters are as follows: the power is 1.5kW, the size of a rectangular light spot is 6mm multiplied by 3mm (length multiplied by width), the scanning speed is 4mm/s, and nitrogen is blown to a molten pool for protection in the cladding process.

The detection steps of the NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating are as follows: the phase composition of the coating was analyzed by XPert-Pro MPD (XRD), the microstructure of the coating cross section was observed by S-4700 field emission Scanning Electron Microscope (SEM), and the microstructure was examined using its attendant energy Spectroscopy System (EDS)The elemental composition of each region in the coating was measured. The microhardness of the coating was measured using a MH-5 type microhardness tester, with a test load of 3009 and a loading time of 10 s. On a HT-1000 high-temperature friction and wear tester, dry sliding friction factors of the two coatings at room temperature, 300 ℃ and 600 ℃ are respectively measured by adopting a ball-disk contact mode, and the relative humidity is 80%. Friction couple of 4mm diameter Si₃And N is added. The hardness of the ceramic ball is 1600HV, and the surface roughness Ra is less than or equal to 0.2 μm.

The invention has the beneficial effects that:

laser cladding NiCr/Cr₃C₂-30%WS₂The coating mainly contains Cr₇C₃γ - (Fe, Ni) and (Cr, W) C, in the presence of a small amount of WS₂CrS lubricating phase. Without addition of WS: the coating layer is made of Cr₇C₃Reinforcing phase and gamma- (Fe, Ni) solid solution. NiCr/Cr₃C₂-30%WS₂The microhardness of the coating is 1000-1240HV_0.3. In between, average 1129HV_0.3About 5 times more than that of the stainless steel matrix and slightly larger than that without the addition of WS₂Coating (1042 HV)_0.3). Both coatings show a decrease in friction factor and an increase in wear rate with increasing temperature (from room temperature to 600 ℃). Adding WS₂The friction factor of the coating was lower than without WS at all temperatures tested₂But the wear rate is only small at 300 c. At room temperature, WS is added₂The wear mechanism of the coating was a slight flaking of the (Cr, W) C phase without addition of WS₂The coating is slightly mixed with abrasive particles and adhesive abrasion; at 300 ℃, WS is added₂The wear mechanism of the coating is the generation and rupture of the lubricating film without the addition of WS₂The coating is adhesive wear; at 600 ℃, WS is added₂The wear mechanism of the coating is abrasive wear without the addition of WS₂The coating is oxidative wear and slight plastic deformation.

Detailed Description

Example 1:

the NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating is prepared from the following raw materials: a hot rolled 0Crl8Ni9 austenitic stainless steel was selected as the base material, having a hardness of about 200HV, and cut into 50mm by 40mm by 8mm samples. Using sandAnd (3) polishing the surface of the substrate by using paper, and cleaning the substrate by using an ethanol solution. The cladding material is Ni80Cr20-Cr₃C₂Cermet powder with NiCr alloy in 30 wt% and solid lubricant WS₂The amount of (B) added is 30%. The preparation method of the NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating comprises the following steps: weighing by an electronic balance, mixing, and ball milling for 2h in a ball mill (QM-SP 04). The mixed powder was then preplaced on a 0Crl8Ni9 matrix using a methylcellulose binder to a thickness of about 1.5 mm. And finally, placing the mixture in a drying box, heating to 80 ℃, and keeping the temperature and drying for 2 h. GS-TFI-10kW type high-power transverse flow CO is adopted by laser cladding equipment₂The laser and the cladding technological parameters are as follows: the power is 1.5kW, the size of a rectangular light spot is 6mm multiplied by 3mm (length multiplied by width), the scanning speed is 4mm/s, and nitrogen is blown to a molten pool for protection in the cladding process. The detection steps of the NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating are as follows: the phase composition of the coating was analyzed by XPert-Pro MPD (XRD), the microstructure of the coating cross section was observed by S-4700 field emission Scanning Electron Microscope (SEM), and the elemental composition of each region in the coating was examined using its attendant Energy Dispersive System (EDS). The microhardness of the coating was measured using a MH-5 type microhardness tester, with a test load of 3009 and a loading time of 10 s. On a HT-1000 high-temperature friction and wear tester, dry sliding friction factors of the two coatings at room temperature, 300 ℃ and 600 ℃ are respectively measured by adopting a ball-disk contact mode, and the relative humidity is 80%. Friction couple of 4mm diameter Si₃And N is added. The hardness of the ceramic ball is 1600HV, and the surface roughness Ra is less than or equal to 0.2 μm.

Example 2:

laser cladding NiCr/Cr₃C₂The coating is mainly made of Cr₇C₃And γ - (Fe, Ni). Joining WS₂Cr removal of coating₇C₃In addition to the main phases of gamma- (Fe, Ni), (Cr, W) C, there is a small amount of WS₂And CrS, due to WS₂Lower decomposition temperature (510 ℃) and oxidation temperature (539 ℃), and most WS₂Decomposed into W and S, part of S reacts with Cr element to form CrS, and W combines with Cr and C to form (Cr, W) C composite carbide. S element does not react with Ni and Fe in the molten pool to generate other sulfides, firstly, because Gibbs free energy of formation of NiS and FeS is far higher than WS₂And CrS, with the highest Cr content in the high-temperature bath and W next, and therefore WS₂And CrS is preferentially precipitated from the molten pool. NiCr/Cr₃C₂-30%WS₂The microhardness of the coating is 1000-1240HV_0.3In between, average 1129HV_0.3About 5 times as much as the stainless steel substrate (200 HV)_0.3) And is slightly larger than without WS₂Coating (1042 HV)_0.3)。

Example 3:

the friction factor of both coatings decreased with increasing temperature and WS was added at all temperatures tested₂The friction factor of the coating is much lower than that of the non-applied coating. This is due to the addition of WS₂In the coating of (A) has WS₂And a CrS lubricating phase, a lubricating transfer film can be formed between the friction pair, the direct high-stress contact between the pair part and the coating is converted into the indirect contact between the pair part and the lubricating film and between the lubricating film and the coating, and the surface of the coating is effectively protected, so that the friction factor is obviously reduced. The wear rate of both coatings increased with increasing temperature, WS was added₂The wear rate of the coating was only less than that of the uncoated coating at 300 ℃. The friction factor and wear rate of the two coatings varied widely, indicating a difference in their wear mechanisms.

Example 4:

NiCr/Cr₃C₂the wear surface of the coating is relatively smooth, without significant pits, scratches and grooves, and is considered to be a slight mixed abrasive and cohesive wear. This is due to the presence of a high volume fraction of (Cr, Fe) in the coating₇C₃The carbide plays a role of a wear-resistant backbone in the wear process, and in addition, due to the connection supporting effect of the gamma- (Fe, Ni) solid solution on the carbide hard phase, the coating has reduced tendency of generating adhesive wear and plastic deformation, and effectively prevents the peeling of carbide particles. However adding WS₂The wear appearance of the coating is more specific and is similar to the structure appearance after chemical corrosion, the chemical corrosion can distinguish the corrosion resistant phase from the easy corrosion phase in the coating, the wear effect is similar to the chemical corrosion, and the hard material in the coating is formedPhases are distinguished from soft phases. EDS analysis identified dark gray hexagonal block areas as (Cr, Fe)₇C₃The light color region is (Cr, W) C. (Cr, Fe)₇C₃. Slightly raised, which mainly plays a role in wear resistance in the coating and protects other soft phases from further wear, while the light-colored (Cr, W) C has a large number of small pits due to the fact that the (Cr, W) C composite carbide is more brittle and the W element is unstable and easily peels off under repeated embedding of the microprotrusions on the surface of the mating part, so that the wear rate of the coating is slightly greater than that of the uncoated WS at room temperature₂The wear mechanism is the micro-spalling of the (Cr, W) C phase.

Example 5:

when the test temperature is raised to 300 ℃, NiCr/Cr₃C₂The wear surface of the coating shows a few relatively large pits, which are due to flaking caused by adhesion, so that the wear mechanism of the coating is mainly expressed as adhesive wear. Adding WS₂The wear surface of the coating is not different from room temperature, but the black lubricating film traces can be seen from the enlarged partial area of the coating, the black lubricating film is positioned in the light-colored (Cr, W) C depression, and the result of EDS analysis shows that the black lubricating film is mainly Cr, W and S elements and is supposed to be WS₂A mixture of CrS. WS in the coating due to the increase in temperature₂The plasticity of the CrS lubricating phase is improved, the CrS lubricating phase is spread on the contact surface under the action of friction force, and simultaneously the CrS lubricating phase is gathered at low-lying (Cr, W) C positions due to uneven surface of the coating, so that the direct high-stress contact part between the mating part and the coating is converted into indirect contact between the mating part and the lubricating film and between the lubricating film and the coating, the effective protection effect is realized on the surface of the coating, and the friction factor and the wear rate of the CrS lubricating phase are far smaller than those of the non-stressed WS₂Coating of (2). The wear mechanism of the coating is manifested by the generation and rupture of a lubricating film.

Example 6:

NiCr/Cr₃C₂the abrasion appearance of the coating at 600 ℃ is greatly changed at room temperature and 300 ℃, and slight plastic deformation and a large amount of fine abrasive dust appear. Wherein Si is selected from Si₃N₄Ceramic ball pair grinding pieceThe transfer is due to the high hardness of the wear parts and the good high temperature stability, and the wear process is mainly the loss of coating material. The high content of O element indicates that the abrasive dust is oxidized violently, and a large number of fine oxide particles form a continuous and uniform oxide transfer film on the friction surface, so that the friction factor can be effectively reduced, the abrasion is reduced, and the abrasion mechanism is oxidation abrasion and slight plastic deformation. WS is added. The abrasion appearance of the coating at 600 ℃, the abrasion surface is slightly scratched, and most of the (Cr, W) C phase with light color is abraded. First, due to WS. Lower decomposition temperature (510 ℃) and oxidation temperature (539 ℃), WS₂Most of the decomposition is oxidized and the lubricating film can not be formed at the temperature; secondly, since (Cr, Fe)₇C₃The hardness of the hard phase is lowered, and (Cr, W) C and the like having relatively low hardness cannot be continuously protected, and together undergo wear of the grinding member, the wear mechanism of which is mainly expressed as abrasive wear.

Claims

1. A NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating is prepared from the following raw materials: selecting hot-rolled 0Crl8Ni9 austenitic stainless steel as a base material, cutting the base material into samples with the hardness of about 200HV and the thickness of 50mm multiplied by 40mm multiplied by 8mm, polishing the surface of the base body by sand paper, and cleaning the base body by using ethanol solution, wherein the cladding material is Ni80Cr20-Cr3C2 metal ceramic powder, the total mass fraction of NiCr alloy is 30%, and the addition amount of solid lubricant WS2 is 30%.

2. The NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating as claimed in claim 1, wherein the preparation steps of the NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating are as follows: weighing by an electronic balance, mixing, putting into a ball mill (QM-SP04) for ball milling for 2h, pre-arranging the mixed powder on a 0Crl8Ni9 matrix by using a methyl cellulose adhesive, keeping the thickness of about 1.5mm, putting into a drying oven, heating to 80 ℃, keeping the temperature and drying for 2h, and adopting GS-TFI-10kW type high-power transverse flow CO laser cladding equipment₂The laser and the cladding technological parameters are as follows: the power is 1.5kW, the size of a rectangular light spot is 6mm multiplied by 3mm (length multiplied by width), the scanning speed is 4mm/s, and nitrogen is blown to a molten pool for protection in the cladding process.

3. The NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating as claimed in claim 1, wherein the detection steps of the NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating are as follows: the phase composition of the coating is analyzed by XPert-Pro MPD (XRD), the microscopic structure of the cross section of the coating is observed by an S-4700 field emission Scanning Electron Microscope (SEM), the element components of each area in the coating are detected by using an attached energy spectrum system (EDS), the microhardness of the coating is determined by using an MH-5 type microhardness tester, the load is tested by 3009, the loading time is 10S, on an HT-1000 high-temperature friction wear testing machine, the dry sliding friction factors of the two coatings at room temperature, 300 ℃ and 600 ℃ are respectively determined by adopting a ball disc contact mode, the relative humidity is 80%, and the friction couple is Si with the diameter of 4mm₃N, the hardness of the ceramic ball is 1600HV, and the surface roughness Ra is less than or equal to 0.2 μm.

4. The NiCr/Cr3C2/WS2 self-lubricating wear-resistant coating as claimed in claim 1, wherein the laser cladding NiCr/Cr3C2-30% WS2 coating mainly contains Cr₇C₃γ - (Fe, Ni) and (Cr, W) C, a small amount of WS2, CrS lubricating phase, no WS added: the coating layer is made of Cr₇C₃The reinforcing phase and the gamma- (Fe, Ni) solid solution, and the micro-hardness of the NiCr/Cr3C2-30% WS2 coating is 1000-1240HV_0.3In between, average 1129HV_0.3About 5 times more than the stainless steel substrate and slightly larger than the coating without added WS2 (1042HV_0.3) The friction factor of both coatings is reduced and the wear rate is increased along with the increase of the temperature (from room temperature to 600 ℃), the friction factor of the coating with the addition of WS2 is lower than that of the layer without the addition of WS2 at all test temperatures, but the wear rate is only lower at 300 ℃, the wear mechanism of the coating with the addition of WS2 is slight stripping of (Cr, W) C phase at room temperature, and the coating without the addition of WS2 is slight mixed abrasive particle and adhesive wear; at 300 ℃, the wear mechanism of the coating with WS2 added is the generation and rupture of the lubricating film, while the wear mechanism of the coating without WS: the coating is adhesive wear; at 600 ℃, the wear mechanism of the added WS2 coating was abrasive wear, while the unadditized WS2 coating was oxidative wear and slight plastic deformation.