Significantly improved weldability in laser welding of additively manufactured haynes 230 superalloys by tailoring microstructure

Abstract

Owing to restrictions on forming dimensions, laser powder bed fusion (LPBF) components will continue to require laser welding in the future. The post-weld thermal cracking of LPBF-Haynes 230 superalloys has become a key issue hindering their assembly in service. In this study, it was found that both the continuous TCP phase and M5Si3 silicides near the crack have a large interface strain with the matrix. Replacing the C and Si atoms with B atoms at the crack reduces the melting point of the carbides and silicides at the grain boundaries (GBs), thereby inducing solidification cracking under the residual tensile stress in the weld waist. The weldability of the alloy is influenced by the grain characteristics of the base metal (BM). Compared to parallel welds, vertical welds are inherited from the BM and exhibit smaller grains. Moreover, by reducing the heat treatment (HT) time and temperature, the grain size and grain misorientation of the BM are reduced and inherited into the weld. The GB area of the weld increases by 37% and the GB energy decreases by 7.3%, increasing the resistance to crack extension. In addition, the decreased HT temperature inhibits the carbide growth at the GBs, thereby reducing the interface strain between the matrix and carbides in the heat-affected zone and correspondingly its cracking sensitivity. This study provides theoretical guidance for improving the laser weldability of LPBF superalloys and will help accelerate the successful application of LPBF superalloy assemblies in engines.

Keywords

• LPBF-Haynes 230
• Welding orientation
• Weldability
• Cracking sensitivity
• Gain morphology
• Grain boundaries