γ-TiAl合金激光熔覆高温自润滑耐磨复合材料涂层研究

Laser Cladding for High-Temperature Self Lubrication Wear Resistant Composite Coatings on γ-Tial Intermetallic Alloy

以NiCr-Cr3C2-40%CaF2(wt.%)复合合金粉末为原料,采用Nd:YAG激光熔覆技术,在γ-TiAl合金基体表面成功制备出了高温自润滑耐磨复合材料涂层,在复合粉体准备时,采用Ni-P化学镀包覆原始CaF2颗粒,以减少其在激光熔覆过程中的分解、蒸发和上浮.采用XRD、SEM和EDS等手段对所制备复合材料涂层的显微组织进行了分析,并测试了TiAl合金及所制备的复合材料涂层的室温滑动磨损性能.结果表明:该复合材料涂层由初生发达树枝状TiC和次生块状Al4C3碳化物增强相以及细小弥散分布的CaF2润滑颗粒均匀分布在塑韧性良好的NiCrAlTi(γ)基体中,其平均显微硬度是基体TiAl合金的2倍以上.CaF2颗粒由于采用Ni-P化学镀包覆而大部分得以保留,并且增强了其与NiCrAlTi(γ)金属基体的相容性,使得该复合材料涂层具有良好的自润滑和耐磨效果.

Ni-P electroless plating was adopted to encapsulate the as-received CaF2 in the preparation of precursor mixed powders of NiCr-Cr3C2-40%CaF2（wt.%） with an aim to form high-temperature self lubrication wear resistant composite coatings on -TiAl substrate. The microstructure of the coating was examined using XRD,SEM and EDS and the friction and wear behavior of the composite coatings was evaluated using a block-on-ring wear tester at room temperature. The coating has a unique microstructure consisting of primary dendrite TiC and secondary block Al4C3 carbides reinforcement as well as fine isolated spherical CaF2 solid lubricant particles uniformly dispersed in the ductile and tough NiCrAlTi（γ） matrix. The average microhardness of the composite coatings is approximately twice greater than that of the TiAl substrate. The good self lubrication and wear resistant capabilities of the laser clad composite coating were suggested to the Ni-P electroless plating and the attendant reduction of mass loss and the increasing of its compatibility with the NiCrAlTi（γ） metal matrix during the laser cladding.