Effect of hot isostatic pressing on microstructure and properties of high chromium K648 superalloy manufacturing by extreme high-speed laser metal deposition

Abstract

High chromium superalloys have good overall mechanical properties and are widely used in critical hot-end components. The current manufacturing process still faces the problem of low forming efficiency. Extreme high-speed laser metal deposition (EHLMD) is a new and efficient additive manufacturing technology that can quickly and directly shape the direct forming of difficult-to-process materials. However, EHLMD still possesses some inter-layer defects in EHLMD alloy due to its excessively fast scanning speed, implying that there is potential for further improvement in its properties. Hot isostatic pressing (HIP) as a post-heat treatment is primarily used for the removal of defects in additive manufacturing components. In this study, the defects, microstructure, and properties of the EHLMD K648 superalloy using Micro-CT, XRD, SEM and TEM under HIP treatment were investigated. The results show that the porosity of the HIP EHLMD K648 superalloy decreased, and slender needle-shaped α-Cr phase, γ′ phase and coarse M6C carbides were precipitated. The tensile strength of the HIP EHLMD K648 superalloy increased by about 240 MPa. However, its plasticity was reduced. To further improve the plasticity of the HIP EHLMD K648 superalloy, subsequent heat treatment was carried out. The outcomes of this study are expected to promote the manufacturing of high-quality chromium superalloys and the development of EHLMD technology.

Keywords

• Hot isostatic pressing
• Extreme high-speed laser metal deposition
• K648 superalloy
• Microstructure
• Properties