NiAl-TiO_2/Bi_2O_3纳米复合涂层制备及宽温域摩擦磨损性能

Preparation and Tribological Properties of NiAl-TiO_2/Bi_2O_3 Nanocomposite Coatings in Wide Temperature Range

采用等离子喷涂(APS)技术制备NiAl-TiO_2/Bi_2O_3纳米复合涂层,通过高能球磨及喷雾造粒制备TiO_2/Bi_2O_3纳米复合喂料,考察纳米结构TiO_2/Bi_2O_3的不同配比对复合涂层显微结构、力学及摩擦磨损性能的影响.结果表明:复合涂层组织致密,各相分布均匀,采用TiO_2/Bi_2O_3纳米复合喂料使涂层呈现出典型的双态区域,涂层结合强度均高于40 MPa.单纯TiO_2纳米喂料制备的复合涂层中低温摩擦磨损性能较差,TiO_2/Bi_2O_3的复配改善了涂层中低温的塑性和摩擦学性能,并提高了涂层的高温润滑性能,其复合涂层磨损率均低于7×10-5 mm^3/(N·m),摩擦系数在800℃时可低至0.1左右,但过高的Bi_2O_3含量会导致涂层硬度降低,磨损率增加.高温摩擦促进了Bi_4Ti_3O_(12)、NiTiO_3等三元氧化物润滑相的生成,其与TiO_2、NiO在磨损表面形成光滑连续的摩擦层使涂层具有优异的高温摩擦学性能.

NiAl-TiO2/Bi2O3 nanocomposite coatings were prepared by atmospheric plasma spraying, where nanostructured TiO2/Bi2O3 feedstock powders were prepared by high-energy ball milling and spray drying. The influence of nanostructured TiO2/Bi2O3 with different mass ratios on microstructure, mechanical and tribological properties of composite coatings was investigated. The results show that all composite coatings possessed dense microstructure and uniform distribution of the phases. The coatings by using nanostrctured TiO2/Bi2O3 composite powders performed the typical bimodal microstructure and displayed higher adhesive strength to substrate（40 MPa）.The composite coating with addition of monolithic TiO2 feedstock powders displayed poor tribological properties at low/mid temperatures. The combination of TiO2 and Bi2O3 improved plasticity and tribological properties of the coatings at low/mid temperatures, and further enhanced the lubricious behavior of composite coatings at high temperatures. For its composite coatings, the wear rate were below 7×10-5 mm3/（N·m） in the whole test temperatures and the friction coefficient was about 0.1 at 800 ℃. With the Bi2O3 content increasing, the hardness of composite coating decreased and resulted in higher wear rate.The sliding process promoted the formation of Bi4Ti3O（12） and NiTiO3 at 800℃,which formed a continuous and complete glaze layer together with TiO2 and NiO on worn surfaces and resulted in excellent tribological properties of composite coatings at high temperature.