Microstructure and high-temperature wear performance of Zr-Y modified silicide coating deposited on TC4 alloy

Abstract

Zr-Y modified silicide coating was deposited on TC4 alloy by the pack cementation process. The microstructure， friction and wear performance， and wear mechanisms of the coating were investigated. The results show that the Zr-Y modified silicide coating has a multi-layer structure， an outer layer consists of TiSi2 and a small amount of ZrSi2， a thin middle layer is TiSi， and an inner layer is a mixture of Ti5Si4 and Ti5Si3. The micro-hardness of the coating is much higher than that of the TC4 substrate and exhibits an obvious decrease tendency from the surface to the interior. The Zr-Y modified silicide coating possesses good anti-wear performance when wearing against GCr15 and Al2O3 balls at a high-temperature of 600 ℃. When wearing against GCr15， the wear rate of the coating is about 3.59×10-5 mm3/（N·m）， which is about 36.6% of that of the TC4 substrate， and the main wear mechanisms are characterized by the adhesive of GCr15 on the coating surface and oxidation wear. When wearing against the Al2O3 ball， the wear rate of the coating is about 9.75×10-5 mm3/（N·m）， which is about 18.9% of that of the TC4 substrate， and the wear mechanisms are fatigue wear， oxidation wear， and adhesion wear.

Keywords

• tc4 alloy
• zr-y modification
• diffusion cementation
• silicide coating
• high-temperature wear
• wear mechanism