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目的：提高等离子喷涂NiCoCrAlY/Al2 O3复合涂层的摩擦性能。方法采用离心喷雾造粒、化学冶金包覆和固相合金化技术制备NiCoCrAlY/Al2 O3和NiCoCrAlY/B4 C复合粉体,通过等离子喷涂技术制备NiCoCrAlY/Al2 O3-B4 C复合涂层。对涂层的显微结构、结合强度和显微硬度进行表征,研究B4 C含量对等离子喷涂NiCoCrAlY/Al2O3-B4C复合涂层力学性能的影响。结果 Al2O3和B4C颗粒包覆了致密的NiCoCrAlY合金层,包覆层厚约3~5μm。等离子喷涂NiCoCrAlY/Al2 O3-B4 C复合涂层呈典型的层状结构,涂层结构致密,各层间结合良好。随着B4 C含量的增加,复合涂层的显微硬度逐渐增大,结合强度逐渐降低,当B4 C质量分数达到30%时,涂层的显微硬度比未添加B4 C时提高了1.4倍,结合强度比未添加B4 C时降低了26%。涂层在拉伸试验中发生了典型的脆性断裂,断裂位置发生在涂层内部。结论向等离子喷涂NiCoCrAlY/Al2 O3复合涂层中添加B4 C,可显著提高涂层的显微硬度,但会使涂层的结合强度有一定程度降低。

ABSTRACT:Objective To improve the tribological properties of NiCoCrAlY/Al2 O composite coating. Methods The NiCoCrAlY/Al2 O3 and NiCoCrAlY/B4 C composite powders were prepared by the technology of spray granulation, chemical and metallurgical coating and solid state alloying. The NiCoCrAlY/Al2 O3-B4 C composite coatings were prepared by atmospheric plasma-spray tech-nology. The microstructure, tensile strength and microhardness were studied in order to investigate the effect of B4 C content on the mechanical properties of atmospheric plasma-sprayed NiCoCrAlY/Al2 O3-B4 C composite coatings. Results The Al2 O3 and B4 C were coated by NiCoCrAlY alloy, respectively, and the thickness of NiCoCrAlY alloy was 3~5μm. The composite coatings consisted of elongated lamellae and they integrated with each other very well. The microhardness of the coatings increased and the tensile strength of the coatings decreased with the increasing B4 C content. The microhardness of the coatings was 1. 4 times higher than that of the coatings without B4 C and the tensile strength of the coatings decreased by 26% as compared with that of the coatings without B4 C, when the B4C content was 30%. Typical brittle fracture occurred in the coatings in the tensile test and the fracture locations were inside the coatings. Conclusion The addition of B4 C into the atmospheric plasma-sprayed NiCoCrAlY/Al2 O3 could improve the microhardness of the coatings, but it also destroyed the tensile strength of the coatings.