Effect of Heat Temperature on Microstructure and Wear Mechanism of Laser Additive Manufactured Hastelloy C22

Residual stress is easily generated in laser additive manufacturing (LAM) alloys due to high-temperature gradient during preparing, which increases the failure risk of materials. A LAM Hastelloy C22 was prepared by rotating strategy in this study, and the wear mechanism induced by heat treatment was investigated. The microstructural results showed that the columnar structure with the size of 1 similar to 4 mu m and the cellular structures with the size of 0.3 similar to 1 mu m were observed in LAM Hastelloy C22. The samples consist of gamma-Ni solid solution. Cr23C6 and the increase of MoSi2 content were found as the heating temperature increased. The mechanical results presented that compared with the as-received LAM Hastelloy C22, the residual stress and wear-rate of the samples heat treated at 600 degrees C, 750 degrees C, and 900 degrees C were reduced by 14%, 49%, 63% and 39.9%, 68.9%, 92.3%, respectively. The wear mechanism showed that heat treatment enhanced the wear resistance of LAM Hastelloy C22 by the integrated oxide layer and supporting effect of MoSi2 and Cr23C6. This research indicated that the microstructural evolution that enhanced the wear resistance of LAM Hastelloy C22 was predominant rather than the reduced effect from relieving residual stress after heat treatment.