Ni–Cr–B–Si–C coatings were deposite

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.
A wide variety of hardfacing alloys is commercially available
for protection against wear. Deposits with a microstructure
composed by disperse carbides in austenite matrix are
extensively used for abrasion applications [3] and are typically
classified according to the expected hardness. Nevertheless,
the abrasion resistance of a hardfacing alloy depends on many other factors such as the type, shape and distribution
of hard phases, as well as the toughness and strain hardening
behavior of the matrix [4]. Chromium-rich electrodes
are widely used due to low cost and availability; however,
more expensive tungsten or vanadium-rich alloys offer better
performance due to a good combination of hardness and
toughness. Complex carbides electrodes are also used; especially
when abrasive wear is accompanied by other wear
mechanisms [5].
Several welding techniques such as oxyacetylene gas
welding (OAW), gas metal arc welding (GMAW), shielded
metal arc welding (SMAW) and submerged arc welding
(SAW) can be used for hardfacing. The most important differences
among these techniques lie in the welding efficiency,
the weld plate dilution and the manufacturing cost of welding
consumables [6].SMAW, for example, is commonly used
due to the low cost of electrodes and easier application. The
present investigation aims to study three commercial electrodes
in terms of their chemical composition, microstructure,
hardness and abrasive wear resistance.