Effect of ultrafine gradient cemented carbides substrate on the performance of coating tools for titanium alloy high speed cutting

Gradient cemented carbides usually used as substrate for coating tools, and the substrate has different gradient layer thickness and grain size, which would affect the cutting performance of the coating tools. In this study, different contents of Co and cubic carbonitride were added, the ultrafine gradient cemented carbides with different gradient layer thickness and grain size were prepared by one-step sintering, and then the CAT films (films containing Cr, Al and Ti, basically.) were deposited on alloy surface by Arc Ion Plating (AIP) in Ar gas atmosphere for titanium alloy high-speed cutting. The influence of Co and cubic carbonitride content on the microstructure of alloy and the cutting performance of coated tools was studied. The results show that the gradient layer thickness could be controlled by changing the Co and cubic carbonitride contents, and then affected the cutting performance. The coating tools enhanced cutting performance obviously by reducing the flank wear in the high-speed Ti-alloy cutting. A thinner gradient layer can be formed in alloys that with a lower Co addition, thus leading to tools chipping during high-speed cutting Ti-alloy. The wear resistance and the cutting performance of the tools could be improved by adding cubic carbonitride. The Co10Ti3-CAT coated tool has the best cutting performance. And the wear resistance of Co8Ti4-CAT coated tool can be increased by 50% compared to substrate. •The coating tools with ultrafine grain gradient cemented carbides substrate was prepared.•The gradient layer thickness could be obtained by controlling the content of Co and cubic carbonitride.•A thinner gradient layer lead to tool chipping during high-speed cutting Ti-alloy.•The effect of substrate on the cutting performance of coated tools was examined.•The coating could improve the wear resistance compared with the uncoated substrate.