Microstructure analysis and cracking mechanism of aero-engine hot-end component K4169 superalloy based on in-situ EBSD test

Abstract

In order to comprehensively examine the premature crack sprouting phenomenon of the aero-engine hot-end component, high-temperature tensile along with in-situ EBSD tests had been performed on alloy K4169. The microstructural and mechanical properties of K4169 high-temperature alloy under different temperature working conditions were also conducted. The results revealed that as the stress intensity factor increases, the stress-strain curve exhibits three distinct stages. With an increase in working temperature, the material's mechanical properties significantly deteriorate, the Laves brittle phase precipitates at the grain boundary, and voids begin to sprout. In-situ EBSD date, it has been discovered that the cracks start to sprout at the concentration of tiny voids formed inside the alloy. Subsequently, after the crack is expanded, it will propagate along the grain boundary, demonstrating the characteristics of intergranular cracks. The predominant type of fracture for the K4169 alloy during the tensile tests at 650 °C and 680 °C is ductile fracture. The fracture mechanism transitions from being ductile to a mixed ductile-brittle model at 710 °C, the operating temperature. This research aims to thoroughly reveal the aero-engine's failure cracking process, which significantly impacts how the engine genuinely operates.