Tool damage and its effect on the machined surface roughness in high-speed face milling the 17-4PH stainless steel

17-4PH stainless steel is a widely used martensitic precipitation hardening stainless steel, and it is a typical difficult-to-cut material. This paper presents an effort to investigate the insert damage process and its effects on the machined surface roughness during the whole process of high-speed face milling the 17-4PH stainless steel. It was found that although the endurance failure, adhesive wear, and diffusion wear altogether contributed to the insert damage, the insert was more inclined to be damaged by the fatigue breakage at the low cutting speed, and by flaking when the cutting speed increased. Notch wear was found during the cutting process for all the milling tests, and the higher cutting speed could severely accelerate its formation. During the cutting process, the average roughness value and its deviation on the machined surface significantly increased after the notch wear. The spindle vibration and big gap between the cutting edge and the workpiece caused by insert damage could lead to the severe chip winding, and further to the generation of scratches and bulges. In the actual production, it is recommended to periodically monitor the tool wear condition and machined surface roughness during the whole cutting tool life cycle, besides exploring appropriate cutting parameters.