Wear-resistant Fe68Cr8Mo4Nb4B16 glass former coatings – From powder production by gas atomization to coating build-up by Laser Powder Bed Fusion

Abstract

Fe-based glassy/crystalline alloys are promising cost-effective protective coatings to increase the service life of engineering components operating in a wide array of aggressive environments. In this work, gas-atomized 53–106 μm Fe68Cr8Mo4Nb4B16 (at.%) powders, produced from commercial-grade precursors, were deposited onto an AISI 1020 steel substrate by Laser Powder Bed Fusion (L-PBF). The coatings were thick (500–700 μm), dense (2–3%vol. porosity), hard (> 1000 HV0.5), metallurgically bonded to the substrate with reduced dilution, and their microstructures were composed of M2B-tetragonal and ferrite within the remaining glassy phase. Nevertheless, some cracks were observed. Good wear resistance characterizes the L-PBF coatings, with a specific wear rate of ~8.40 × 10−5 mm3/N·m, much lower than the value obtained from the soft (~114 HV0.5) AISI 1020 substrate, 1.91 × 10−4 mm3/N·m. The wear mechanism observed on the coating surfaces was predominantly abrasive and by fracture originated from preexisting cracks. In addition to abrasive wear, the occurrence of oxidative wear was also observed on the worn surface of the substrate. The protective coatings produced by L-PBF proved to be an interesting approach to protect and to repair the surface of steel substrates from wear, besides highlighting the use of L-PBF for coating production.