Papers by Keyword: Wear Performance

Abstract: An attempt is made in this work to improve the performance and tool life of the tungsten carbide (WC) coated aluminium chromium nitride (AlCrN) via physical vapor deposition (PVD) method. Various deposition temperatures ranging from 250, 350, 400, and 450 oC were investigated to evaluate the characteristic of coated carbide. Prior to the deposition process, WC surfaces were treated in Murakami’s solution for 15 minutes followed by Caro’s solution for 10 seconds to improve the coating adhesion on WC by the dissolution of cobalt (C); roughened the carbide surface. The thickness of the coated AlCrN increases proportional with higher deposition temperatures (from 1.14 μm to 2.18 μm) and homogenously coated. While XRD analysis observed the presence of AlN and CrN phases attributed to AlCrN coating. The hardness of the coated carbide was highest at 450 oC deposition temperature (1325 HV). The qualitative scratch test following ASTM D 3363 indicated that higher temperature (400 oC and above) provides good adhesion characteristics between AlCrN coating and WC.

Abstract: The copper-molybdenum disulfide composites were prepared by powder metallurgy under argon sintering atmosphere. The effects of nickel plating on the surface of the molybdenum disulfide on the friction and wear properties of the composites were studied. Friction and wear experiments with different frictional speeds and loads were carried out on the surface micromechanical testing system of UNMT-1 material. The microstructure and friction/wear morphology of the materials under different conditions were observed by laser scanning confocal microscopy(LSCM), scanning electron microscopy (SEM) and optical microscopy(OM). The results show that the sintering temperature increased from 720 °C to 920 °C, and the microhardness and wear properties were obviously improved. The reaction products of nickel-plated molybdenum disulfide and nickel-free samples were the same at different sintering temperatures, whereas the product content was the same. There was a significant difference between the micro-morphology and the surface of the molybdenum disulfide. The friction coefficient of the nickel-plated molybdenum on the surface of the molybdenum disulfide was relatively high, the wear was relatively serious, the wear surface was relatively rough, and the unnickel-plated sample exhibited good friction and wear properties.

Abstract: The paper studied the friction and wear performances of n-Na₂B₄O₇/ion nitrocarburized duplex layer at different frequences. It is found that at frequence 10 Hz, 20 Hz, 30 Hz, respectively, the friction factor and volume loss of the duplex layer is 64%, 60%, 50% and 97%, 91%, 95% less than that of the intermediate frequency quenched surface, respectively, which indicates that the n-Na₂B₄O₇/ion nitrocarburized duplex layer has more excellent friction reduction and wear resistance performances than the intermediate frequency quenched surface under CD15W-40 oil lubricating at different frequences. This because that the chemical reaction films including oxide, BN and so on formed on the friction surface play the solid lubrication function, and the n-Na₂B₄O₇ particles on the friction surface play the "Micron nanobearing" function.

Abstract: The cutting performance and wear mechanisms of whisker-toughening ceramic cutting tools synthesized by carbothermal reduction process have been studied when cutting the hardened alloy steel 40Cr. It is indicated that the wear resistance of ceramic tools is affected by the molar ratio of C and N in tool materials. At low cutting speed, the main tool wear mechanisms are abrasive wear and oxidation wear. At middle and high cutting speed, the tool wear mechanisms are controlled by abrasive wear, adhesive wear, diffusion wear and oxidation wear simultaneously. Adding whiskers to the matrix material is one of the effective means to improve the wear resistance of ceramic cutting tools.

Abstract: Influence of arc discharge to the contact strip of carbon-carbon composites was orthogonally studied on the HST-100 tribo-tester under electric current, which simulated working conditions of the pantograph-wire system used in electric railway. The regression equation between specific wear rate and arc discharge were obtained and analyzed through the non-linear regression and orthogonal design. The results of the experiments show that a power function between specific wear rate and arc discharge was obtained. Microstructure and phase composition were observed and analyzed by scanning electron microscope(SEM), energy dispersive X-ray spectrum(EDS) and temperature sensor. The results revealed that the arc discharge dissipation seriously affects tribological characteristics of the carboncarbon composites. The temperature of some local contact points beyond their melting point with the electric arc heat effect, and give rise to the desposite carbon and friber carbon were vaporazated, which form the lubrication film on the wear surface, and with the augmant of the arc discharge, the area of lubrication film of carbon was decrease. Therefore, the main wear form of the arc erosion of the carbon-carbon composites is evaporate erosion and material transfer.

Abstract: Ti and TiN were deposited on mold steel 3Cr2W8V by PVD, then processed with the technology of electron beam surface alloying. The microstructure of modified and the influence of modified layer on wear performance of 3Cr2W8V were studied. The result shows that the section hardness of coating Ti material has increased by 35% at most when the times of treatment reach 25, the distribution of the section hardness is waved, the pick point of section hardness is at depth of 100μm to 200μm, The friction of coating Ti layer is decrease by 50% at most when the times of treatment reach 20, and the abrasion loss is totality descend by about 80%;the section hardness of coating TiN material has increased by 35% at most also when the times of treatment reach 25, the pick point of section hardness is at depth of 150μm to 250μm, the friction factor of material is waving with descend while the times of bombardment increased; the abrasion loss is totality descend by about 90%.

Abstract: Plasma arc, a kind of high energy density beam, is proposed as one kind of surface treatments in this paper to improve the adhesive properties of the chromium coatings to the steel substrate. Scratch tests are used to obtain the critical load (Lc) of the coatings. The wear behaviors are evaluated by a reciprocating ball-on-flat wear machine and the wear tracks of the coating were characterized by scanning electronic microscope (SEM). Results show that plasma arc treatment could promote the adhesive and the wear performances of the chromium coatings. Optimal value of Lc and the wear resistance of the treated coatings could be obtained when the average output energy density of the plasma arc (E) grow to 1.05×105J/m2. The comparative study indicates that the promotion of the adhesion could be attributed to the formation of the inter-diffused alloyed layer and the improved hardness distribution. This promotion then contributes to the improvement of the wear performance, which makes up, even exceeds the loss of it caused by the drop of the coatings hardness.

Abstract: The wear resistance samples of brazed single crystal diamond with Ni-Cr filler alloy were prepared, using high frequency induction brazing and vacuum brazing methods. By wear test of brazed single crystal diamond, the wear performance of the samples with different brazing processes was studied. The test result indicates that the wear performance of the high frequency induction brazed diamond samples is better than that of the vacuum brazed diamond samples. Because of different brazing processes, the wearing pattern of diamond varied; the wear course of the vacuum brazed diamond samples in the initial wear period were abnormal and the failure modes is different.