Analysis of processing 40Kh13 martensitic stainless steel billet obtained by wire electron beam additive manufacturing

The authors investigated the microstructure and mechanical properties of the samples obtained by the method of wire electron beam additive manufacturing (WEBAM), and their machinability by milling forces using the Taguchi method. Grains of previous austenite and annealed martensite were observed in the samples in various directions. The grains of the previous austenite grow along the surfacing direction and exhibit a pronounced orientation. On the lateral surface of the sample, the grains of the previous austenite are columnar, their hardness is approximately 505 HV 0.1 . On the upper surface of the sample, the grains of the previous austenite are isometric, their hardness is approximately 539 HV 0.1 . The degree of transformation into martensite varies in different parts of the sample. In the part close to the lateral surface, martensite is shallower and the previous austenitic grain boundaries are not observed. Its hardness is approximately 514 HV 0.1 . In the lower part of the sample, due to multiple thermal cycles, martensite decomposes, while its hardness is low and is approximately 480 HV 0.1 . In the upper part of the sample, martensite and the previous austeni­tic grain boundaries are observed, the hardness is approximately 513 HVelectron beam additive manufacturing, microstructure, hardness, machinability, martensitic stainless steel, Taguchi method. Due to the high hardness of the sample during climb milling, a stronger impact of the cutting edge on the sample leads to an increase in cutting force. Due to the low plasticity of the sample during conventional milling, a decrease in the volume of material pressed into the back surface of the tool leads to a decrease in cutting force. As the feed rate to the tooth increases, deformation of the material increases, the temperature increases, which leads to a decrease in the material strength. Reducing the material strength slows down the growth of cutting force.