Microstructure and Wear Behavior of Fe-Based Amorphous Metallic Coating by HVOF Thermal Spraying

To manufacture a protective coating with low thermal conductivity and good frictional wear performance, a Fe₅₉Cr₁₂Nb₅B₂₀Si₄ coating was designed and produced by high velocity oxygen fuel (HVOF) spraying; the properties and performance of this coating where then compared with those of a commercially available AISI 316L stainless steel coating. In the as-deposited state, both coatings exhibit dense layered structures with porosity below 1% and slight oxidation. The microstructure of the Fe-based coating has an amorphous matrix and some precipitated nanocrystals. The result is that the designed Fe-based coating has a thermal conductivity (2.66 W/m·K) that is significantly lower than that of the 316L stainless steel coating (5.87 W/m·K). Based on its advantageous structure, the Fe-based coating exhibits higher microhardness, reaching 1258±92 HV. The friction coefficient and wear rate of the Fe-based coating show an increase at 200°C followed by a decrease at 400°C, due to the evolution of the wear mechanism at different temperatures. The dominant wear mechanism of the Fe-based coating at room temperature is fatigue wear accompanied by oxidative wear. At 200°C, due to the existence of “third body” abrasive wear, the wear process was accelerated. The large-area oxide layer is likely responsible for the decrease of friction of the coating at 400°C.