Study on the Microstructure and Fatigue Behavior of a Laser-Welded Ni-Based Alloy Manufactured by Selective Laser Melting Method

Low-cycle fatigue and creep-fatigue tests were conducted at 815 °C on laser-welded, selective laser melted (SLM) Inconel 625 test specimens. The results showed that the microstructure of the welding zone was mainly composed of columnar dendrites, which grew epitaxially from the weld line and exhibited better fatigue and durability resistance than the non-welded SLM alloy. The low-cycle fatigue life and creep-fatigue life decreased with increasing test stress. Both fatigue and creep-fatigue properties were better for laser-welded SLM Inconel 625 specimens than non-welded specimens. High-density intergranular cracks formed in the γ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma$$\end{document} matrix at base material, which contained many intergranular precipitates. Precipitation of intermetallic δ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\delta$$\end{document}, γ″\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma^{\prime\prime}$$\end{document}, and the intergranular carbides was responsible for the higher hardness of the fatigue and creep-fatigue specimens.