Influence of Stress Relief Annealing on the Hardness and Sliding Wear of Invar and Invar-10wt%TiC Manufactured by Laser Powder Bed Fusion

This study investigates the influence of TiC addition to Invar manufactured using laser powder bed fusion. Stress relief annealing was performed to relieve residual stresses induced during the LPBF process. Preliminary sliding wear tests were conducted before and after the heat treatment. The hardness of the Invar and Invar-10wt%TiC in the as-built state was 170HV10 and 317HV0 respectively. After annealing the hardness of Invar decreased by 8% while that of Invar-10wtTiC decreased by 5%. This decrease is attributed to thermal softening of the Invar as seen from x-ray diffraction which revealed lattice recovery. The wear rates of the Invar and Invar-10wt%TiC in the as-built state were 4.48 x 10-7 mm3|Nmm and 1.78 x 10-7 mm3|Nmm respectively, which increased by 7.3% and 14.8% post annealing. Despite the minor decreases after annealing the TiC had increased the hardness and wear resistance of the Invar significantly.