Papers by Keyword: Wear Property

Abstract: The effect of DLC film on tribological properties of C/C composites was investigated with a ball-on-disk tribometer in dry air, compared with the result of specimen without DLC film. The DLC film was prepared on the surface of C/C composites substrate by plasma enhanced chemical vapor deposition method (PECVD). After PECVD, structural characterization of the film, adhesion strength of film to substrate, surface morphology and linear wear were studied by Raman spectroscopy, Rockwell-C apparatus, Scanning Electron Microscopy (SEM) and Optical Microscopy (OM), respectively. The result showed that the film deposited on the surface of C/C substrate exhibited typical Raman spectroscopy fingerprints of DLC films and a good adhesion to the substrate surface was found. A stable friction coefficient was observed during the friction tests. With the DLC film, the friction and wear properties of C/C composites were improved significantly. The average friction coefficient of the C/C specimen with DLC film (0.08637) was reduced by 65.56% than that of the one without DLC film (0.2508) and the linear wear was decreased by 84.7% ( from 148.47μm to 22.71 μm) as well.

Abstract: Using the specially designed mechanochemical ball-mill equipment, the ultramicro molybdenum nitride powders were prepared from pure molybdenum powders in ammonia atmosphere at room temperature by high-energy ball milling. The results show that the mass ratio of grinding media to powder was 4:1 and after milling for 30 h, the Mo₂N of fcc structure was obtained, and the average particle size of powders was around 100 nm. It is found that the chemisorption of ammonia onto the fresh molybdenum surfaces created by milling was the predominant process during solid–gas reaction，and the change of Mo electronic undersaturation induced by the grain refining also accelerated the bonding between Mo and N. The coating was formed on the 40Cr steel base using plasma spray method by mix Ni60 alloy powders and ultramicro Mo₂N powders of 5wt%, 10wt% and 15wt%, respectively. Coating abrasion test under the condition of dry-grinding , 2h wear time and 300N test load showed that the wear-resisting property of coating added with ultramicro Mo₂N powders could be improved greatly, and the wear-resisting property of coating increased with the increase of Mo₂N content. In the abrasion process, the evenly distributed ultramicro Mo₂N particles play the dispersion strengthening and self-lubricating role in the coating.

Abstract: The Al/Gr/SiC hybrid composites have attracted a considerable attention owing to their high wear resistance combined with a low friction coefficient. In these composites graphite acts as a solid lubricating agent and lowers the friction coefficient. However, it reduces the mechanical properties of the composite. The presence of hard SiC particles in these hybrid composites increases the hardness and strength and compensates for the weakening effects of graphite. Powder metallurgy (P/M) is an important processing technique for processing of these MMCs but requires a relatively long mixing time for obtaining a uniform distribution of graphite and SiC particles in the matrix alloy. In the present study for the first time a new method, namely "in situ powder metallurgy (IPM)" is applied for preparation of Al/SiC/Gr hybrid composites. In this work, the effects of different contents (0-40 vol.%) of SiC particles on the morphology and size distribution of the IPM produced Al/Gr/SiC powder mixtures containing 9 vol.% of graphite particles was investigated. Then Al/Gr/SiC compacts were prepared by cold pressing of different powder mixtures and after sintering, the effects of SiC content on the density, microstructure, hardness and wear properties of the resultant hybrid composites was investigated.

Abstract: GCr15 alloy produced by hot-forged is subjected to equal channel angular extrusion (ECAE) process at 950°C. The microstructure of GCr15 steel via ECAE and annealed is studied by an optical microscope. The effect of ECAE and annealing on the wear properties of the alloy is also investigated. The results show that the grain size reduced from 50 mm to 10 mm via one pass ECAE, and the hardness of the alloy is increased. The wear mass loss of the alloy is greatly reduced due to the grain-refinement after ECAE and annealing.

Abstract: In this paper, cobalt, tungsten and molybdenum were co-diffused into the surface of T8 steel by double glow discharge technique. A carbide layer with M6C＋MC was formed on T8 steel. Under the carbide layer was a diffusion layer of W,Mo,Co. Hardness of carbide layer is high over 1200~1400 HV_0.025 and can improve to 1400~1600 HV_0.025 after solution and ageing treatment. Hardness of the diffusion layer is only 400~550 HV_0.025, but it can improve to 800~1000 HV_0.025 after solution and ageing treatment. The carbide layer combides with the substrate in metallurgy and can not peel off from the substrate. The carbide layer on T8 steel possess same good tribological properties of M2 steel.

Abstract: The friction and wear properties of AISI 52100 steel and DLC coatings were evaluated while being lubricated with silicone oil, PAO and PAG lubricants by using a reciprocating ball-on-disk sliding UMT tester. The morphologies of original surface and worn surfaces for the DLC and Ti doped DLC coatings were observed by using a scanning electron microscope. The results show that the DLC coatings have better tribological properties than AISI 52100 steel under silicone oil, PAO and PAG lubrication conditions. In addition, the DLC coatings have much better wear resistance than the AISI 52100 steel.

Abstract: Cu-14Al-X alloys was made into powder and then the powder was coated onto the surface of AISI 1045 steel respectively via plasma spraying and laser cladding technologies. Microstructure and phases of the coating were investigated by EPMA, XRD, SEM et al. Friction and wear properties of the two coatings were tested by RFT- friction and wear testing machine. The results indicates that the two coatings all consists of β′, α, K and γ2 phases and the structure of laser cladding is more evenly distributed. Under the condition of boundary lubrication, abrasion mechanism of laser coating remains abrasive grain abrasion. There is also adhesion abrasion under the condition of high load. While abrasion mechanism of plasma coating is slight abrasive grain abrasion and adhesion abrasion under low load. With the load increasing, adhesion abrasion intensifies. In a word, microstructure of laser coating is more even and compact.

Abstract: A new kind of high temperature solid lubricant coating was synthesized by adopting new technique and using graphite, MoS2, Sb2O3 and Al2O3. Its tribological behaviors and lubricate mechanism were studied by means of wear testers. The experiment results show that the friction coefficient of the solid lubricant coating decreases with the increase of load and slightly increases with the raise of temperature. The solid lubricant coating still has good lubrication in 400 .

Abstract: VC coating was prepared on the surface of Cr12MoV cold working die steel by TD process, and its friction and wear properties were researched with HSR-2M type high-speed reciprocating friction and wear tester, the effects of load on friction and wear properties were discussed, and the wear surface morphologies were observed with SEM. The experimental results shown that fatigue wear and adhesive wear are mainly wear mechanism of VC coating, and the different parts have an influence on wear mechanism; When cracks occurs, the crack growth is the combined result of mutual influence of elastic-plastic crack growth and fatigue crack growth; There is no relationship between friction coefficient and load, and the wear rate increases with the load.

Abstract: A friction and wear experiment was carried out at different areas of single crystal silicon under same surface roughness. Friction mechanisms at different area were analyzed by STM and 3D profiler. The result showed that the friction and wear properties were obviously different at different area although they had same surface roughness. The friction and wear properties of the single crystal silicon where closest to inner-cycle internal were best while the farther from the inner-cycle silicon area or closer to crystal silicon cylindrical, the worse friction and wear properties were. Abrasive wear and adhesive wear were the primary wear mechanisms.