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.

► Dilution from the steel substrate increased Fe content of Ni–Cr–B–Si–C deposits. ► Higher Fe contents reduced the size and content of Cr borides. ► As dilution increased, Cr borides with higher content of Fe became dominant. ► High Fe contents diminished the amount of Ni–Si–B eutectic phases. ► Dilution from the steel substrate degraded the hardness of Ni–Cr–B–Si–C deposits.