Fe-based amorphous/nanocrystalline coatings with smooth, compact interior structure and low porosity were fabricated via supersonic plasma spraying (SPS). The coatings showed outstanding corrosion resistance in a 3.5% NaCl solution at room temperature. In order to analyze the effect of annealing treatment on the microstructure, corrosion resistance and microhardness, the as-sprayed coating was annealed for 1 h under different temperatures such as 350, 450, 550 and 650 °C, respectively. The results showed that the number of oxides and cracks in the coatings presented an obvious increase with increasing annealing temperature, and the corrosion resistance of the coatings showed an obvious reduction. However, the microhardness of coatings showed an important increase. The microhardness of the coating could reach 1018 HV when the heat treatment temperature reached 650 °C. The X-ray diffraction (XRD) results showed that there appeared a number of crystalline phases in the coating when the heat treatment temperature was at 650 °C. The crystalline phases led to the increase of the microhardness.

The WC and high chromium cast iron (HCCI) welded layers were prepared on Q235 low carbon steel by hardfacing technique in order to improve high-temperature performance. The microstructure and mechanical properties of the welded layer were investigated. It was found that Fe3W3C is the major strengthening phase of the WC welded layer. Furthermore, a high-temperature three-body abrasive wear experiment was designed and conducted on the welded layers. The results show that the wear resistance of the WC welded layer was much better than that of the HCCI welded layer at both room and high temperatures. During the high-temperature abrasive wear process, the Fe3W3C phase can effectively strengthen the matrix and hence, contribute to improved wear resistance.

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