Effect of in situ TiC Generation on the Ambient/High Temperature Wear Resistance of TiC-Ni25 Composite Coatings
To improve the wear resistance of ductile iron,TiC-Ni25 metal composite coatings are prepared by laser fusion coating using in situ generation and direct TiC addition.The effects of different Ti additions on the microstructure,microhardness and friction and wear properties of TiC-Ni25 composite coatings at 25 ℃,200 ℃ and 400 ℃ are respectively investigated.The results show that Ti,which has strong thermal conductivity and promotes graphitization,reduces the generation of lysite in the bonding area between the composite coating and the matrix.And Ti,which is a strong carbide forming element,also promotes the in situ generation of TiC,which plays a role for combination of fine grain strengthening,intergranular strengthening and diffusion strengthening in the coating.The addition of Ti improves the wear resistance of the coating,controlls the porosity and cracks defects of the composite coating.Due to the competition between the hardness enhancement of TiC generated in situ and the toughening effect of enriched Ti,the microhardness of the 5％Ti-10％TiC-Ni composite coating is higher than that of 2％Ti-10％TiC-Ni and 8％Ti-10％TiC-Ni coatings.The friction and wear properties of the 5％Ti-10％TiC-Ni composite coating are excellent at above temperatures because of the formation of dense oxide film,which strengthens the protection of the wear area.The increases in friction coefficient,wear volume and wear rate of the composite coatings at 200 ℃ are due to the formation of rough oxide film,which reduces the wear resistance.The main wear mechanisms of the composite coatings are abrasive wear and slight adhesive wear at 25 ℃,and oxidation wear,fatigue wear and adhesive wear at 200 ℃ and 400 ℃.
laser claddingcomposite coatingTiCfriction and wear
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