Structure and wear resistance of hot-rolled Fe–Cr–B coatings

<jats:p>Introduction. Austenitic steels are widely used in mining, railway, and chemical industries due to their high toughness and corrosion resistance. However, their service life under severe wear conditions is limited, which necessitates the development of effective surface hardening techniques that preserve the ductility of the substrate. The purpose of this study is to investigate the microstructure, mechanical properties, and tribological behavior of Fe–Cr–B-based coatings fabricated by non-vacuum electron beam cladding on AISI 321 steel followed by combined treatment (quenching and hot rolling). Materials and methods. Cladding was performed using two powder mixtures with different boron contents: C1QHR (1 g B) and C2QHR (2 g B). After cladding, the samples were quenched from 1,100 °C and subsequently hot-rolled at 950 °C. The microstructure was examined using scanning electron microscopy, and the phase composition was determined by X-ray diffraction. Mechanical properties were evaluated by microhardness measurements, while tribological characteristics were assessed using a ball-on-flat dry sliding wear test. Results and discussion. The combined treatment was found to promote the precipitation of submicron (Fe,Cr)23C6 carbides within the austenitic matrix and the formation of (Fe,Cr)2(C,B) carboborides. The coating with the higher boron content (C2QHR) exhibited a hardness of 484 ± 20 HV, which is 2.4 times higher than that of AISI 321 steel. The wear resistance of the C2QHR coating is 5.3 times higher than that of the AISI 321 steel substrate. The main mechanisms enhancing the wear resistance of the coatings are precipitation hardening due to carbide precipitation, as well as the formation of borides and carboborides. Conclusions. The combination of quenching and hot rolling of the layers obtained by non-vacuum electron beam cladding forms a wear-resistant protective layer on the surface of AISI 321 steel.</jats:p>