In situ synthesis of Fe-based alloy clad coatings containing TiB₂-TiN-(h-BN)

Fe-based alloy coatings containing TiB₂-TiN-(h-BN) were synthesized in situ on Q235 steel substrates by a plasma cladding process using the powders of Fe901 alloy, Ti, and h-BN as raw materials. The effects of Ti/h-BN mass ratio on interfacial bonds between the coating and substrate along with the microstructures and microhardnesses of the coatings were investigated. The results show that the Ti/h-BN mass ratio is a vital factor in the formation of the coatings. Free h-BN can be introduced into the coatings by adding an excess amount of h-BN into the precursor. Decreases in the Ti/h-BN mass ratio improve the microstructural uniformity and compactness and enhance the interfacial bonds of the coatings. At a Ti/h-BN mass ratio of 10/20, the coating is free of cracks and micropores, and mainly consists of Fe-Cr, Fe₃B, TiB₂, TiN, Ti₂N, TiB, FeN, FeB, Fe₂B, and h-BN phases. Its average microhardness in the zone between 0.1-2.8 mm from the coating surface is about Hv_0.2 551.5.