镍基自润滑涂层的制备及拉伸结合强度研究

Synthesis and Tensile Binding Strength of Ni-based Self-lubricating Coatings

采用等离子喷涂与粉末冶金方法分别制备了PS304、PM304镍基自润滑涂层,并对涂层的组织、拉伸结合强度进行了研究。结果表明:采用等离子喷涂制备的PS304涂层组织粗大、孔隙率高、润滑相与强化相分布不均匀。而采用高能球磨与真空烧结技术制备的PM304涂层组织均匀、致密、粒子明显细化。拉伸试验表明:PS304的拉伸结合强度较低,拉伸断口不仅出现在涂层与基底的结合处、也出现在涂层内部;而PM304的拉伸结合强度较高,涂层与基底之间结合良好、结合方式为冶金结合,拉伸断口主要出现在涂层内部。PM304涂层拉伸强度增大的原因主要为:(1)致密度提高;(2)尖锐孔隙数量降低;(3)Ag与Ni Cr之间形成冶金结合;(4)Ni Cr基体中析出粒子的弥散强化作用使得Ni Cr基体强度提高。

The microstructure and tensile binding strength of Ni-based self-lubricating coatings PS304 by plasma spraying and PM304 by powder metallurgy were studied. The result shows that the PS304 coating prepared by plasma-spraying has a coarse microstructure and high porosity. The lubricant phase fluoride and strengthening phase Cr2O3 are distributed unevenly. However, the microstructure of PM304 coating prepared by mechanical milling and vacuum sintering is uniform and dense, and the size of particles is much finer. The tensile test shows that the PS304 coating has a low tensile binding strength. The tensile fracture occurs not only in the interface of coating and substrate, but also appears in the internal of the coating. The PM304 coating has a higher tensile binding strength, and a good metallurgical bonding can be obtained between coating and substrate. The tensile fracture mainly appears in the internal of the coating. The higher tensile binding strength of PM304 coating is mainly due to 4 reasons, including the increase of density, the decrease of the sharp pores number, a metallurgical bonding formed between Ag and Ni Cr, and the dispersion hardening effect of fine particles precipitated from the Ni Cr substrate which increases the strength of the Ni Cr substrate.