Continuous and Pulse TIG Arc Treatment for Surface Hardening of WAAM-MIG Parts

Abstract

Continuous and pulse TIG arc treatment of MIG-based wire arc additive manufactured (WAAM-MIG) parts has been investigated. A hybrid method is proposed for selective surface hardening applications. It presents an opportunity for immediate heat treatment in the WAAM process, thereby enhancing overall workflow effectiveness. The influence of peak current, base current, and pulse frequency was studied on surface hardness, depth of hardened region, and cooling rate. A maximum hardness of 428 HV was achieved, yielding an increase of ~ 71% from ~ 250 HV of as-deposited low alloy steel. As the yielded hardness increased, its depth was observed to decrease, e.g., the depth of the hardened region was limited within the range of 0.2–0.5 mm at maximum hardness. Similarly, a 1 mm hardened depth limited the surface hardness to ~ 350 HV. Hardness improvement could be attributed to martensite microstructure formation and showed a strong dependency on the mode of operation and associated cooling rate. © The Indian Institute of Metals - IIM 2024.