Crack Control and Microstructure Properties of K465/Gh4169 Fabricated by Selective Laser Melting

The K465 nickel-based high-temperature alloy, which contains a high content of Al+Ti elements, tends to form eutectic microstructure (γ+γ′) with a low melting point during the casting process. This leads to the development of significant residual tensile stresses upon rapid cooling, making the prepared specimens highly prone to cracking under these tensile stresses. In this study, crack-free specimens were achieved by incorporating GH4169 alloy into the K465 alloy and fabricating a GH4169/K465 alloy through selective laser melting. It was observed that the occurrence of cracks can be effectively controlled by reducing the content of Al+Ti elements. Additionally, the rapid melting and cooling involved in the selective laser melting process hinder the formation of eutectic microstructure and prevent the occurrence of liquation cracking. The organization and properties of the GH4169/K465 alloy were investigated, revealing that the alloy consists of a matrix phase (γ), white Laves precipitates, and spherical particle precipitates (NbTi4). Mechanical tests were conducted on three specimens, namely 1GH1K, 7GH5K, and 3GH1K, demonstrating elongation values exceeding 20%, tensile strength surpassing 1000 MPa, and a reduction in hardness from 329 HV to 285 HV.