EFFECT OF HEAT TREATMENT DURATION AND COOLING CONDITIONS ON TENSILE PROPERTIES AND HARDNESS OF SELECTIVE-LASER-MELTED...

The mechanical properties of cobalt-chromium (Co-Cr) alloys produced through selective laser melting (SLM) can be enhanced by the application of the post-heat treatment, but it is still unclear how long the heat treatment should last and how the cooling rate affects the tensile properties and hardness of the alloy. Aim of this study - investigate the effects of heat treatment for one hour and six hours, respectively, at 1150 C, and three cooling conditions (AC, FC, and WC), on the tensile strength, elongation, and hardness of SLM Co-Cr alloy specimens. Thirty-five Dumbbell shaped specimens (50×12×2 mm) (ISO 6892-1:2016), and thirty-five rectangular-shaped specimens (34×13×1.5 mm) ISO (22674:2016) were manufactured and divided into seven groups, based on the use of heat or cold and the duration of both. Tensile strength and Vickers hardness tests were performed on the specimens. When it comes to tensile strength, the (FC1) group took the bottom spot with a score of (991.21 MPa) while the control group came out on top, boasting an impressive (1362.41 MPa). When it came to elongation, the control group had the lowest score (4%), while the best-treated group scored (17%). The lowest and highest value of tensile strength was similarly affected. Water-quenched groups showed better tensile properties and hardness than other groups. As a result, increasing the cooling rate is an effective way to improve the ductility and hardness of the SLM Co-Cr alloy.