On preventing HAZ cracking in laser welded DS Rene 80 superalloy

Abstract

The heat affected zone (HAZ) cracking behaviour in a laser beam directionally solidified (DS) Rene 80 nickel based superalloy subjected to preweld heat treatments was studied. The HAZ cracks in the alloy are grain boundary liquation cracks caused by liquation reaction of both non-equilibrium secondary solidification product, MC carbides and equilibrium solid state reaction product, γ′ precipitates. In contrast to theoretical prediction based a preweld heat treatment that reduced grain boundary liquid film thickness did not result in a lower HAZ cracking, which can be related to concomitant reduction in the ability of the base alloy to relax welding stress. In addition, formation of intergranular M5B3 boride particles in preweld alloy appeared to have aided cracking susceptibility by lowering grain boundary liquation temperature and widening the brittle temperature range in the HAZ during cooling. Based on the analysis of the results, application of a new preweld heat treatment that prevents the formation of the intergranular borides and induces moderate base alloy hardness resulted in a nearly crack free HAZ in laser welded DS Rene 80 superalloy.

Microstructure evolution and grain refinement mechanism of Inconel 601H alloy welded joints under compound physical fields of vibration and rapid cooling

“…According to relevant research, the HAZ liquation cracking has a great relationship with the width and grain size of HAZ. The HAZ liquation cracking was easy to occur in many nickel-based alloys during welding [20][21][22]. Idowu [23] showed a significant relationship between liquation cracking and grain size.…”

Additive Manufacturing and Characterization of René 80 Superalloy Processed Through Scanning Laser Epitaxy for Turbine Engine Hot‐Section Component Repair

“…Larger grain sizes in EQ alloys are beneficial from a creep strength perspective due to the reduction of overall grain boundary area. Under rapid heating, the grain boundary phases are unable to dissolve fully into the surrounding matrix and their partial dissolution leads to the formation of a low melting point eutectic and melting of the grain boundary region . Rush et al showed that an increase in the grain size lowers the ductility and causes more segregation of melting point depressing elements at the grain boundary, resulting in an increase in average crack length in the cold metal transfer process, where material was welded in the solutionized state.…”

Characterization of laser‐treated Rene 41 surface due to B4C and SiC particles at surface prior to laser treatment

“…They showed that laser treatment resulted in different hot crack lengths in the heat‐affected zone, which depended on local microstructural configuration in the close region of the treated region. The prevention of heat‐affected zone cracking in laser‐treated nickel‐based superalloy was examined by Osoba et al . They demonstrated that application of a pre‐weld heat treatment prevented the formation of the intergranular borides while resulting in a nearly crack free heat‐affected zone in the laser‐treated layer.…”

“…Hot cracking in the heat-affected zone of laser-treated nickel-based superalloy was investigated by Matijasevic-Lux et al [13] They showed that laser treatment resulted in different hot crack lengths in the heat-affected zone, which depended on local microstructural configuration in the close region of the treated region. The prevention of heat-affected zone cracking in laser-treated nickel-based superalloy was examined by Osoba et al [14] They demonstrated that application of a pre-weld heat treatment prevented the formation of the intergranular borides while resulting in a nearly crack free heat-affected zone in the laser-treated layer. The age-hardening mechanism of nickelbased superalloy subjected to a laser rapid forming was studied by Xiaoming et al [15] They indicated that tensile strength after the laser treatment process increased considerably as compared to the strength of untreated workpiece.…”