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October 22, 2025Open Access

Comparison of Microstructure, Mechanical Properties, and Wear Properties of Cold Sprayed and HVOF WC-10Co4Cr Coatings on 4340 Steel Substrates

JZJiamin ZengSun Yat-sen University XJXiankun JiHefei University of Technology YYYingjing YuanNorthwestern Polytechnical University

Key Points

The cold sprayed WC-10Co4Cr coatings exhibit a porosity of less than 0.1%, significantly lower than the 0.3% of HVOF coatings.
Microhardness of the cold sprayed coatings reached 1617.2 HV0.3, showing a remarkable 50% increase compared to the HVOF coating's hardness.
The sliding wear rate of cold sprayed coatings is only 0.17 × 10−5 μm3/N·m, just 40% of the wear rate seen in HVOF coatings.
Despite higher performance in wear resistance and hardness, the bond strength of the cold sprayed coating was lower at 35 MPa compared to the HVOF's 73.5 MPa.

Abstract

This paper investigates WC-10Co4Cr coatings on 4340 steel prepared by conventional HVOF and novel cold spraying (CS) under optimal process parameters to address low wear resistance. The results show that the CS WC-10Co4Cr coating porosity is less than 0.1%, while the HVOF WC-10Co4Cr coating porosity is about 0.3%. The WC phase in the CS coating did not change, whereas the WC phase in the HVOF coating underwent decarburization and a new W2C phase was formed. The microhardness of the CS WC-10Co4Cr coating reaches 1617.2 HV0.3, which is about 50% higher than that of HVOF WC-10Co4Cr coating of 1061.3 HV0.3. The sliding wear rate of the CS WC-10Co4Cr coatings is 0.17 × 10−5 μm3/N·m, which is 40% of that of the HVOF coatings. The CS coating’s fretting wear rate is 1.28 μm3/N·m, which is 40% faster than that of HVOF coating. However, the bond strength of the CS WC-10Co4Cr coating (35 MPa) is lower than that of the HVOF coating (73.5 MPa). Overall, the WC-10Co4Cr coatings prepared by the CS process have higher hardness, denser coating microstructure, and better sliding wear resistance than those prepared by the conventional HVOF process.

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