A new way to produce Al + Cr coating on Ti alloy by vacuum fusing method and its oxidation resistance

An Al + Cr coating successfully produced by the vacuum fusing method was proposed for improving the oxidation resistance of Ti–6Al–4V alloy specimens. Unlike powder pack cementation, this technique was much more effective and cheap without the need for long time diffusion, and the Al concentration and the thickness of vacuum fusing coating layer could be controlled by adjusting powder mixing ratio and adding the immersed times, respectively. Compared with the specimen with an Cr-modified aluminide coating, the oxidation resistance of the specimens with vacuum fused Al + Cr coating was about two times than that of the specimens with Cr-modified aluminide coating. During oxidation, Cr additions suppressed metastable θ-alumina formation. It is only one phase α-alumina scale that developed on the vacuum fused Al + Cr coating surface, while a single metastable θ-alumina scale formed on the Cr-modified aluminide coating surface.