Study on microstructure of laser coaxial fuse GH4169 superalloy

Through wire-fed coaxial additive manufacturing technology, laser melting deposition experiments of GH4169 superalloy under different offset amounts were carried out, and the influence laws of different offset amounts on the microstructure morphology and microhardness of the deposited layers were systematically analyzed. The research results show that under different offset conditions, no porosity defects were observed inside the deposited layers, and the forming quality was good. During the forming process of the second pass, the laser heat input partially melted the deposited layer of the first pass, achieving good metallurgical bonding between the two passes. The melting region at the bonding interface between the deposited layer and the substrate exhibited a typical "W"-shaped fusion line, indicating uniform molten pool flow and heat conduction distribution. There is an obvious grain transition zone between the substrate zone and the additive zone, where the grain size is relatively fine and the microstructure is dense. In the additive zone, a large number of continuously distributed elongated precipitated phases were precipitated between the dendrites, oriented along the dendrite direction. The microhardness test results show that the hardness of the second pass was slightly higher than that of the first pass, and the overall hardness showed an increasing trend, which is mainly closely related to the heat accumulation effect during the pass-by-pass deposition process and the distribution characteristics of the precipitated phases.