Study on microstructure of GH4169 superalloy fabricated by laser coaxial wire deposition

Through the laser-wire coaxial additive manufacturing technology, laser melting deposition experiments of GH4169 superalloy under different offsets were carried out, and the effects of different offsets on the microstructure morphology and microhardness of the deposited layers were systematically analyzed. The results indicate that under different offset conditions, no porosity defects are observed inside the deposited layers, and the forming quality is good. During the forming process of the second pass, the laser heat input partially melts 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 exhibits a typical “W”-shaped fusion line characteristic, indicating that the molten pool flow and heat conduction distribution are uniform. 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 precipitate between the dendrites, which are directionally arranged along the dendrite direction. The microhardness test results show that the hardness of the second pass is slightly higher than that of the first pass, and the overall hardness exhibits 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.