Study on high speed milling of steam turbine blade materials - Difference in cutting characteristics by alloying elements of stainless steel

In this study, high speed milling of stainless steel was tried for purpose of high efficiency cutting of a steam turbine blade. In the experiment, cutting tool used TiAlN coating radius solid end mill made of cemented carbide. Diameter of end mill is 5mm. Corner radius is 0.2mm. Cutting speed carried out at 100m/s～600m/s. Work pieces was used in the experiment are four kinds of stainless steel which alloy elements differ. Mainly, content of chromium and nickel is different. There are many researches about high speed milling [1, 2]. However, the researches which examined relationship between alloy elements of stainless steel and cutting characteristics on high speed milling using small diameter endmill are few. As the results, in the case of stainless steel containing much nickel, tool life becomes short in high speed cutting area. This reason is nickel has low thermal conductivity. Because the cutting point temperature becomes higher. If the coating removes, wear becomes large rapidly. In other words, maximum limit value of cutting speed was found to be dependent on heat resistance temperature of the coating. On the other hand, Chromium has the effect of improving the abrasion resistant of the workpiece. However, Flank wear was not increased in a low cutting speed area. In the range of this experimental condition, chromium didn't influence tool life. When cutting point temperature is below heat resistant temperature of the coating, it is thought that effect of the coating is maintained. Namely, it was found that appropriate cutting speed followed heat resistant temperature of the coating.