Microstructure and Tribological Property of TiC-Mo Composite Coating Prepared by Vacuum Plasma Spraying
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Xiaoqian Guo, Yaran Niu, Liping Huang, Heng Ji, and Xuebin Zheng (Submitted March 4, 2012; in revised form May 4, 2012) TiC-based composite coating using Mo as an additive has been fabricated by vacuum plasma-spraying, and then the phase composition and microstructure of TiC-Mo composite coating were investigated. Wear resistance of the TiC-Mo composite coating was comparatively studied with pure TiC coating. The experimental results showed that the microstructure of the TiC-Mo composite coating was relatively homogeneous and compact, exhibiting typical lamellar structure of plasma-sprayed coating. Orientated columnar grains of TiC can be found in the composite coating, and a (Ti, Mo)C transition phase was also observed. Due to the formation of (Ti, Mo)C transition phase, strong interface between TiC and Mo splats was obtained, which positively influenced the wear performance of the composite coating. As compared with pure TiC coating, the TiC-Mo composite coating exhibited improved wear resistance both at low and high loads. Wear mechanisms for the TiC coatings have been changed by adding Mo element.
Keywords
Mo, titanium carbide coating, tribological behavior, vacuum plasma spray
1. Introduction Titanium carbide (TiC) has been a frequent choice for wear-resistant applications owing to its high hardness (Mohs 9-9.5), high melting point (3433 K), and superior chemical stability (Ref 1-3). However, the inherent brittleness of TiC restricts its wide-range applications, which makes it constantly applied as a coating onto metallic materials to utilize the mechanical strength of metals. TiC coatings/films fabricated by physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques have been studied for engineering applications since the last decade (Ref 4). PVD and CVD coatings/films are popular for their dense microstructure and good bonding to substrates; however, the low deposition rate and extremely thin thickness (normally £ 10 lm) are unavoidable (Ref 5). Plasma-spraying technique has also drawn attention for fabricating TiC coatings (Ref 6, 7). Thick TiC coatings (thickness normally 100-1000 lm) could be successfully deposited by atmospheric plasma spraying (APS) with high deposition rate (Ref 8). However, APS technique also has its limitations. During the spraying process, plasma plume with external air could Xiaoqian Guo, Yaran Niu, Liping Huang, Heng Ji, and Xuebin Zheng, Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, Peoples Republic of China. Contact e-mails: [email protected] and [email protected].
Journal of Thermal Spray Technology
cause serious oxidation of TiC particles, and as a result, the phase composition, microstructure, and preferred properties of TiC could be affected significantly. Vacuum plasmaspraying (VPS) process, which is carried out in controlled atmosphere, especially inert gas environment, sufficiently inhibits the oxidation of powders providing an opportunity to produc
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