TiC生成方式对激光熔覆镍基涂层组织和性能的影响

分别以TiC粉和Ti+C粉为原料,采用外加法和原位法制备了TiC/Ni激光熔覆涂层,分析了TiC生成方式对涂层物相组成、微观组织、硬度和磨损性能的影响。结果表明,涂层的物相组成不受生成方式的影响;但Ti+C质量分数高于30%时,原位法涂层无法成型,而外加法可获得40%TiC的涂层。外加法涂层中TiC以原料TiC为主,少量溶解析出的结晶TiC;而原位法涂层中TiC全部为结晶析出,分布更加均匀,颗粒细小,枝晶数量增多。原位法涂层的平均硬度和耐磨性均优于相同TiC含量的外加法涂层;涂层中TiC含量(质量分数)由20%增至30%时,涂层硬度升高,耐磨性下降,生成方式引起的磨损性能差异由5%降至0.6%。

Effects of TiC Formation Modes on Microstructure and Performance of Ni-based Laser Cladding Coatings

TiC/Ni laser cladding coatings were fabricated respectively by externally added TiC powders and in-situ formed TiC with Ti+C powders. Effects of TiC formation modes on phase composition, microstructure, microhardness and wear resistance of the coatings were analyzed. Results show that TiC formation modes have little influence on phase composition of the coatings. The TiC/Ni coating is unable to form in-situ when the mass percentages of Ti+C powders in raw materials are above 30%, while the coating with 40% externally added TiC can be obtained successfully. TiC in the ex-situ coating is composed of TiC in raw materials and a small amount of crystalline TiC based on dissolution-precipitation mechanism. While TiC in the in-situ coating is crystalline, which is finer and distributed more uniformly compared with that in the ex-situ coating. Furthermore, more TiC dendrites were observed in the in-situ coating. The average microhardness and wear resistance of the in-situ coating are better than that of the ex-situ coating when the TiC content is the same. With increasing TiC content from 20% to 30%, the hardness of the coating increases, the wear resistance decreases, and the difference in wear resistance caused by the formation method decreases from 5% to 0.6%.