Improvement in mechanical properties of Rene 104 superalloy during laser additive manufacturing process

Abstract

In this study, laser additive manufacturing (LAM) was used to fabricate Rene 104 superalloy parts. Serious crack defect was found in the LAM Rene 104 superalloy part and there was a large gap between the LAM Rene 104 part and the one by powder metallurgy forming (PM) in mechanical properties such as tensile strength, micro-hardness and density. To improve the mechanical properties of Rene 104 superalloy, several different pre and post processing methods were used in the LAM process. Experiments are conducted to investigate the effects of different processing methods on the crack defect, microstructure evolution and mechanical properties. It is found that there are still many cracks in the LAM Rene 104 part if only preheating is used. Thus, except for preheating, a new cooling strategy is proposed to slow down the cooling rate of both substrate and deposited part. With the slow cooling rate, the cracks in the LAM part are significantly eliminated and only some micro cracks still remain. To further improve the performance of the LAM Rene 104 superalloy, a real-time hammering method is provided on the basis of decreasing cooling rate. The experimental results demonstrate that the proposed method can fabricate LAM parts with excellent mechanical properties comparing to the PM ones.