Influence of Ni content on the microstructure and reciprocating wear of Fe-based/B4C composite coating by vacuum cladding

Abstract

Fe-based/B4C composite coatings without and with 1–5 wt% Ni (Ni-free and Ni-added, respectively) were fabricated on the surface of ASTM 1045 steel via vacuum cladding. The effects of Ni addition on the microstructure, hardness and reciprocating wear of Fe-based/B4C composite coatings were investigated by optical microscopy (OM), electron probe microanalysis (EPMA) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), hardness tester and reciprocating wear tester. The results showed that all coating composed of α-Fe, γ-Fe, (Fe, Ni) solid solution, M23(C, B)6, and M2B phases, which indicated that Ni addition into the coating had little impact on the composition of the M2B-type borides and M23(C, B)6-type carboborides in the coating. However, with the increase of Ni addition, the hardenability of the coating matrix was improved, and toughness phase of martensite was formed. Meanwhile, the morphology of strengthening phases gradually changed from chrysanthemum-like to intermittent net-like. When Ni addition was 3 wt%, the irregular block and net-like strengthening phases were uniformly distributed in the coating matrix of martensite, which made the microhardness of the coating relatively stable and the average hardness was 920 HV. Under different applied loads, non-significant variations in the coefficient of friction were observed. The wear volume of the coating with 3 wt% Ni addition was the minimum, which was only 2 × 10−3 mm3 under the applied load of 30 N, showing the best sliding wear performance. The wear morphology and elements distribution analysis suggested that the main wear mechanism of dry sliding wear of the coatings with different Ni addition were oxidative, adhesive and abrasive wear.