Microstructure and mechanical properties of direct laser metal deposited Haynes 282 superalloy

Abstract

Direct laser metal deposition (LMD) is a directed energy deposition based additive manufacturing process developed for a wide range of applications that are currently employed in aerospace, medical and automotive sectors. In the present study, a 100 mm × 15 mm × 25 mm block of Haynes 282 (HY282) superalloy was fabricated by LMD. The effect of several post-deposition heat-treatments revealed a wide range of strength and ductility of HY282 samples that can be tuned to obtain the best material properties. The microstructure and mechanical properties of the as-deposited and heat-treated specimens are investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray-diffraction (XRD), uniaxial tension test, and micro-hardness measurements. The SEM and XRD investigation revealed the formation of columnar dendrites having [001] growth direction opposite to the heat flow direction during LMD. The as-deposited samples revealed the presence of γ, γ′, Ti and Mo-rich MC, and Mo-rich M6C phases with the strengthening γ′ phase having an average precipitate size of 8.25 nm in the interdendritic region. The EDS investigation revealed the uniform distribution of Ni, Al, Cr, Co in the overall deposit with high segregation of Ti and Mo in the interdendritic regions. The corresponding hardness of 294 HV, yield strength of 633 MPa, and 31.5% elongation was recorded in the as-deposited samples that were better than the as-cast properties. The LMD specimen heat-treated at 788 °C for 16 h revealed a homogeneous distribution of γ′ with an average size of 31 nm with a globular and Chinese script type carbides interconnected in the interdendritic region. The corresponding hardness of 410 HV, yield strength of 894 MPa, ultimate tensile strength of 1200 MPa, and 18% elongation was recorded. These results establish that HY282 is an attractive material for the LMD process.