Dilution effects in laser cladding of Ni-Cr-B-Si-C hardfacing alloys

Ni-Cr-B-Si-C coatings were deposited by laser cladding and effects of additional iron (Fe) as a result of dilution from the steel substrate were investigated. It was found that for Fe contents of up to around 25 wt%, chromium borides with higher Fe fractions could form but further increase of the Fe content to over 40 wt% entirely suppressed the precipitation of primary Cr borides. Similarly, the Ni-Si-B eutectics were diminished as dilution increased. By reducing the amount of chromium borides and Ni-Si-B eutectics, excessive iron contents degraded the hardness of Ni-Cr-B-Si-C coatings from 800 to 500 HV. These findings can be used to explain the role of dilution in evolution of microstructure and properties of Ni-Cr-B-Si-C coatings and to tune the processing parameters to obtain the desirable deposits. (C) 2012 Elsevier B.V. All rights reserved.