A novel method to eliminate Laves phases in Ni-based superalloy laser cladding by in-situ theory

Abstract

During the laser cladding of GH4169 superalloy, the high concentration of Nb elements in the interdendritic regions promotes the formation of large, chain-like Laves phases, which significantly deteriorate the mechanical properties of the cladding layer. Traditional methods for eliminating Laves phases usually involve optimizing the solidification conditions of molten pools and applying post-cladding heat treatments. However, solely adjusting the solidification conditions cannot completely eliminate the Laves phases, and post-cladding heat treatment may alter the microstructure of the substrate. This study proposes a new in-situ elimination technology to effectively remove Laves phases by leveraging the reaction between C produced by WC decomposition and Nb segregated in the interdendritic region at high temperatures. Additionally, high-frequency ultrasonic vibration enhances the uniform distribution of WC particles and promote the diffusion of C, further facilitating the in-situ reaction. The results indicate that the in-situ elimination technology effectively eliminated the Laves phase. As WC content increased, more C reacted with Nb at high-temperature, reducing Nb segregation in the interdendritic regions and subsequently decreasing Laves phase content. At 30 % WC content, all Laves phases were transformed into carbide-reinforced phases. Moreover, higher ultrasonic vibration current improved the uniform distribution of unmelted WC particles. The coating with 30 % WC content exhibited optimal wear resistance, with the wear width and wear depth reduced by 22.97 % and 40.45 %, respectively. Furthermore, the hardening ratio of the coating after wear is only 4.48 %, indicating superior performance. The research results indicate that the in-situ elimination theory can effectively eliminate the Laves phase. This provides a new solution approach for eliminating the Laves phase formed during laser cladding of GH4169 Ni-based superalloy.