Influence of Ni additions on microstructure, non-magnetic properties, and wear resistance of Fe–Mn-Cr alloy deposited by metal-cored arc welding

In this study, we propose Fe–Mn-Cr/Ni as an economical drill collar overlay material applied via metal-cored arc welding (MCAW). A series of Fe–Mn-Cr/Ni overlay alloys with different Ni contents were prepared by MCAW, and their microstructure, non-magnetic, and wear properties were systematically investigated. The results show that the addition of Ni element can effectively improve the austenitization of the Fe–Mn-Cr/Ni overlay alloy and inhibit the formation of ferromagnetic hexagonal martensite (ε) and body-centered ferrite (α), thus improving the non-magnetic properties of the Fe–Mn-Cr/Ni overlay. With the increase of Ni addition from 0.6 to 4.7 wt.%, the average grain size gradually increases from 21.69 to 49.97 µm, and the overlay microstructure gradually evolves from columnar-like ε-martensite to wide ε-martensite band and eventually almost austenite. This change in microstructure as Ni content increases contributes to the reduction of relative permeability from 2.225 to 1.057 due to the increased austenite contents, at the cost of increased wear rate from 2.61 × 10⁻⁵ to 4.55 × 10⁻⁵ mm³·N⁻¹·m⁻¹ due to the decay of wear-resistant ε-martensite skeleton. By controlling the Ni content, this work demonstrates the potential of preparing Fe-based austenitic wear-resistant layers with high Mn content and broadens the scope of austenitic non-magnetic deposited alloys for surface overlay strengthening or repairing of Fe-based non-magnetic drilling tools.