Wear performance of diamond coated WC-Co tools with a CrN interlayer

In this paper we report the wear performance of diamond coated WC-Co cutting tools with a CrN interlayer by machining Al-Si alloys. Diamond films were deposited on both WC-6%Co (Arno) and WC-10%Co (Sandvik) substrates with a CrN interlayer using the hot filament chemical vapor deposition technique. Adhesion assessment by the indentation technique shows that there was no major delamination of diamond coatings on any substrate at a load of 196 N. The stress field image of the region close to the indentation marks using Raman spectral imaging shows the splitting of the first order Raman line as well as a shift in the peak position to a higher frequency. Machining experiments of diamond/CrN/WC-6%Co tools with the Al-Si alloy (AlSi17Cu4Mg) workpiece shows a wear performance of VBmax = 0.1 mm at tc = 960 s, however, their performance in impact tests was not as high. On the other hand, machining experiments of diamond/CrN/WC-10%Co tools with an Al-Si alloy workpiece showed an excellent wear performance (VBmax = 0.17 mm at tc = 960 s), alongside an improved coating-substrate interface fatigue strength. A combined study using indentation, turning and impact tests demonstrates the potential advantage of diamond coatings on WC-10%Co substrates with a CrN interlayer for machining of Al-Si alloys and other high impact applications.