Microstructure and mechanical properties of crack - free Ni - based GH3536 superalloy fabricated by laser solid forming

Abstract

Laser solid forming (LSF) was used to fabricate dense and crack-free specimens from solution-strengthened nickel-based superalloy GH3536 in this study. Tensile, and fatigue crack growth (FCG) testing was carried out in both horizontal and vertical build orientations with the condition at 25 °C and 500 °C. Three regions can be detected in the specimen: the additive manufacturing zone (AM), the heat affected zone (HAZ) and the substrate. M23C6 and M6C carbides were found in the specimens, only a small amount of hole defects was observed in the samples, and no cracks were found. The tensile test results show that the specimens have obvious anisotropy, and the horizontal specimens displayed higher strength (up to 855.3 MPa ultimate tensile strength at 25 °C). It is worth noting that there is no obvious anisotropy in the FCG rates of the specimens in different directions, and only when the ΔK is about 45–60 MPa m1/2, the FCG rates of the vertical specimens are higher. The increase in temperature will significantly reduce the tensile performance and increase the FCG rate of the specimens.