The Investigation On The Microstructure And Wear Mechanism Of In-situ Synthesis TiC-TiB₂ Particulates Reinforce Metal-matrix Composite Coatings By Gas Tungsten Arc Cladding

Fe based metallic ceramic coating reinforced by in-situ synthesized TiC and TiB₂ particulates was prepared by means of gas tungsten arc cladding(GTAC) using Ti, B₄C and Fe powders as the binding materials. The cladding F2(wt.%,40%Fe, Ti/B₄C=3/2) was chosen as the optimal clad materials, and optimal GTAC parameters were obtained. The microstructure, micro-hardness and wear resistance were investigated using SEM, TEM, XRD, Micro-hardness Tester and Friction& Wear Tester respectively.The results showed that TiC and TiB₂ distributed inα-Fe dispersively. Excellent bonding between the coating and the Q235 steel substrate was uniform, continuous and almost defect-free. The microstructural analysis showed that there were three regions in the layer, namely: the clad zone, the dilution zone and heat-affected zone, and a diffusion zone was found in the upper part of heat-affected zone.A kinetic investigation performed allowed us to conclude that solid-state diffusion is the mechanism governing the synthesis process. TiC was the first phase precipitated, while TiB₂ formation occurred afterwards. The TiC particle existed in the form of dendrite flower-like and cubic morphology. The TiB₂ existed in the form of clubbed and hexagonal shape. And the content of TiB₂ was higher than that of TiC.The friction coefficient of GCr15 and coatings in pair with the W₆Mo₅Cr₄V₂ alloys varied with load. The friction coefficient of GCr15 became bigger with the load increasing. In contrast, the friction coefficient of coatings decreased with the increase of the load. The argon arc cladding composite coatings had higher hardness and excellent wear resistance under dry sliding wear test conditions.