Coating - substrate bonding after HVOF thermally spraying WC-Co on to a Ti-6%AI-4%V alloy

摘要

In earlier papers the present authors have studied the interfacial structures developing when using the high velocity oxy-fuel (HVOF) technique to thermally spray WC-Co coatings on to a variety of substrates including steel, Al-4%Cu alloy and pure copper [1-3]. The results indicated that in order to obtain good adhesion between the coating and the substrate partial melting or full melting of the substrate was required so that a metallic bond could develop between the liquid phase in the coating and the melted region of the substrate. In order to test the validity of this conclusion a similar experimental approach to that used previously has been adopted, however the substrate material chosen was Ti-6%A1-4%V alloy. It is generally accepted that the highest temperature attained in the liquid phase when thermal spraying WC-Co is of the order of 1550 °C. This is well below the liquidus of the Ti-6%A1-4%V alloy and a few tens of degrees below the solidus, thus it would seem unlikely that melting of the titanium alloy would occur.