Fabrication and characterization of Fe-based amorphous coatings prepared by high-velocity arc spraying

Fe-based coatings with a high amorphous content were firstly developed by the traditional twin wires arc spray technology. In consideration of empirical rules, including the multi-component system, an optimal concentration of small atoms, negative heat of mixing and an appropriate atom size mismatch among the main components, the cored wires were designed to contain eight elements, which have an optimized atomic volume strain criterion lambda(n), in range of 0.14-0.21, to render the coatings a high glass forming ability. Then the coatings were prepared using the above-designed cored wires through a rapid arc spray melting and solidification process. Crystalline phases could not be identified from the XRD patterns within the XRD resolution limits, suggesting that the as-sprayed coatings were approximately comprised of fully amorphous phases. With a dense structure and a low porosity of only 2%, the amorphous Fe-based coatings exhibited an attractive combination of high hardness (900-1100 HV0.3) and superior bonding strength (44.9-54.8 MPa). The coating at lambda(n) = 0.21 had the lowest Gibbs free energy difference Delta G, exhibited the largest super-cooled liquid region Delta T-x, Lu's criterion factor gamma value and the heat of crystallization (Delta H) values, which indicating the highest GFA. (C) 2015 Elsevier Ltd. All rights reserved.