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진공 정밀주조한 Inconel 713C 합금의 조직과 기계적 성질에 미치는 열처리의 영향
유병기,최학규,박흥일,정해용 한국주조공학회 2020 한국주조공학회지 Vol.40 No.2
The effect of a heat treatment on the microstructure and mechanical properties of Inconel 713C alloy vacuum investment castings were investigated. The microstructure of the as-cast state was observed, showing well-developed dendrite structures and distributed carbide particles and solidified massive precipitates in the grain or grain boundary during solidification, in this case the ′phase and MC particles. During a heat treatment, the phase matrix was reinforced by solid solution elements, carbide particles from the film morphology precipitated along the grain boundary, and many micro-precipitates of second ′phases 0.2 m~2 m in size were newly formed in the phase matrix according to SEM-EDS analysis results. The tensile strength at a high temperature (850oC) decreased slightly becoming comparable with the room-temperature result, while the hardness value of the specimen after the vacuum heat treatment increased by approximately 19%, becoming similar to that of the as-cast condition. However, the impact values at room temperature and low temperature (-196oC) were approximated; this alloy was mostly not affected by an impact at a low temperature. In the observations of the fracture surface morphologies of the specimens after the tensile tests, the fractures at room temperature were a mix of brittle and ductile fractures, and an intergranular fracture in the inter-dendrite structure and some dimples in the matrix were observed, whereas the fractures at high temperatures were ductile fractures, with many dimples arising due to precipitation. It was found that a reinforced matrix and precipitates of carbide and the ′phase due to the heat treatment hadsignificant effects, contributing greatly to the excellent mechanical properties.
강민정(Minjung Kang),김철희(Cheolhee Kim),김영민(Young-Min Kim) 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.1
During welding of Ni based superalloy, hot cracking was usually happen in the fusion zone of a weld. In this study, the laser weldability of Inconel 713C alloy for the turbocharger wastegate valve (WGV) was evaluated with various welding conditions, such as laser power, welding speed, shielding gas. Welding conditions were optimized by bead-on-plate (BOP) and butt joint welding. For the evaluation of laser weldability, bead shapes and weld microstructures were investigated and tensile test was conducted. The fracture surfaces were investigated for the understanding the cause of the fracture.