Experimental study on additive/subtractive hybrid manufacturing of 6511 steel: process optimization and machining characteristics

The additive/subtractive hybrid manufacturing (ASHM) method, which takes the advantages of both additive manufacturing (AM) and precision subtractive machining (SM), is a promising technique for the surface quality improvement of an AMed part. However, machining characteristics and the residual stress evolution during the ASHM process have not been investigated in detail for the materials with phase transformation. In this study, an experimental study is conducted on manufacturing of a 6511 martensitic stainless steel with the ASHM method that combines selective laser melting (SLM) and end milling. The process window of SLM is determined in terms of the relative density. Milling forces, surface roughness, and residual stress of the ASHM samples with different cutting parameters are studied. The phase transformation of the martensitic steel is considered in the analysis of the residual stress. It is found that the surface residual stress state and distribution can be controlled by the milling parameters. This study provides guidance for the optimization of the process parameters for ASHM to manufacture martensitic stainless steel.