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利用Ti与AlN之间的高温化学反应,在TC4钛合金表面激光原位合成了TiN/Ti3Al基金属间化合物复合涂层.借助XRD和SEM分析了涂层的物相组成和显微组织.结果表明,涂层主要由TiN和Ti3Al组成.当Ti与AlN摩尔比为4:2时,涂层中TiN含量随激光功率密度的增大而减小;Ti与AIN摩尔比为4:1时,TiN含量随激光功率密度的增大而增大.TiN增强相点阵常数的精确计算显示,涂层中TiN相出现晶格畸变现象,结合EDS分析表明,TiN固溶的Al含量随功率密度的增加而减小.SEM分析表明,TiN增强体的生长形态随着激光功率密度的增大由棒状逐渐向颗粒状转变.当Ti与AlN的摩尔比为4:1,激光功率密度为15.28 kW·s·cm~(-2)时,涂层表面的宏观形貌较好,微观组织无气孔和裂纹,试样截面显微硬度自基体至涂层表面变化平缓,涂层平均显微硬度达到844 HV_(0.2),约为基体合金的3.4倍.
TiN / Ti3Al-based intermetallic compound coating was synthesized by laser in-situ on the surface of TC4 titanium alloy by the high temperature chemical reaction between Ti and AlN.The phase composition and microstructure of the coating were analyzed by XRD and SEM. The results show that the coating mainly consists of TiN and Ti3Al.When the molar ratio of Ti to AlN is 4: 2, the content of TiN decreases with the increase of laser power density. When the molar ratio of Ti to AIN is 4: 1, The TiN content increases with the increase of the laser power density.The accurate calculation of the lattice constants of the TiN strengthening phase shows that the lattice distortion of the TiN phase in the coating occurs and the EDS analysis shows that the content of Al in the solution of TiN varies with the power density Increase and decrease.SEM analysis showed that the morphology of TiN reinforcements changed from rod to granular gradually with the increase of laser power density.When the molar ratio of Ti to AlN was 4: 1, the laser power density was 15.28 kW · s ~ cm ~ (-2), the macroscopic morphology of the coating surface is good, the microstructure is free of pores and cracks, the microhardness of the cross section of the sample changes gently from the substrate to the coating surface, and the average microhardness of the coating reaches 844 HV_ (0.2), about 3.4 times the base alloy.