Mechanical and tribological properties of Cr-Nb double-glow plasma coatings deposited on Ti-Al alloy

摘要

Double-glow plasma (DGP) coatings are recommended for metallic components to mitigate the damage induced by complex working conditions in previous studies. In this paper, Nbrich (Cr-Nb_4) and Cr-rich (Cr_4-Nb) -alloyed layers were formed onto the Ti-Al substrate via a DGP process to enhance its wear resistance. Scratch and Nano-indentation tests were used to evaluate the mechanical properties of the coatings. The tribological behaviour of the coatings were investigated using a pin-on-disc tribometer by rubbing against the GCr15 ball. Results from surface analysis techniques showed that the coatings mainly comprised Cr, Nb and Cr_2-Nb phases, and were well bonded to the substrate. The hardness of the Cr-Nb_4 coating was 11.61GPa and the Cr_4-Nb coating was 9.66 GPa which all higher than that of the uncoated Ti-Al which was 5.65 GPa. However, the critical load of the Cr_4-Nb coating ～21.64 was higher than that of the Cr-Nb_4 coating ～17.6. And the specific wear rate of Cr-Nb_4 coating, Cr_4-Nb coating and uncoated Ti-Al were 3.54 × 10~(-4), 0.01 × 10~(-4) and 1.53 × 10~(-4)mm~3 N~(-1) m~(-1) respectively. The low-wear mechanism of the coatings is discussed in detail in this paper.