Wear behavior and surface roughness analysis of carbide tools with varying coating for high-speed milling of compacted graphite cast iron

With stricter emissions regulations and higher engine performance demands, the high-quality processing of Compacted graphite cast iron (CGI) for the automotive industry has received more and more attention. Coated carbide tools are now widely used to cut CGI. The coating material is an essential factor affecting processing efficiency and cost. However, the processing adaptability and wear mechanism of tool coating materials to CGI has yet to be thoroughly studied. CGI milling experiments in this paper were carried out using different coated carbide tools. The effect of coating materials on milling forces, tool wear and surface roughness for coated tools under different cutting parameters were compared and evaluated. It is found that TiAlN/TiN coated tools have the best cutting force, tool wear, and surface roughness, followed by TiAlN/AlCrN coated tools. The analysis of the tool failure process shows that bonding and oxidation are the main wear mechanisms of TiAlN/TiN, TiAlN/AlCrN, and TiCN coated tools, while bonding is the primary wear mechanism of TiN/TiCN/Al 2 O 3 and TiN/MT-TiCN/Al 2 O 3 coated tools. The wear mechanism of the flank is groove and coating wear, and the wear process is removing the coating material on the tool surface and chipping the unprotected cutting edge. When comparing the tool durability, it was found that the tool life of TiAlN/TiN was extended by 17.4 %–28.6 % (v = 150 m/min, f = 0.1 mm/z, ap = 0.4 mm) and 5.3 %–17.6 % (v = 250 m/min, f = 0.2 mm/z, ap = 1 mm), respectively, compared to the rest of the coated tools. Based on the average surface roughness (Ra) values obtained for the same cutting distance, TiAlN/TiN performed better than the rest of the coated tools by 8.1 %–40.1 % (v = 250 m/min, f = 0.1 mm/z, ap = 0.5 mm). In addition, the study of the machined surface roughness shows that the surface roughness is affected by the flank wear width and the cutting fluctuation caused by it.