The High Velocity Air Fuel (HVAF) thermal spraying process has been used to deposit cermet coatings, represented by WC-CoCr and WC-NiCr, onto a steel 40 substrate. The major objective of this study is to make a comparison between these two coatings to indicate their performance to resist the cavitation erosion-corrosion when tested using ultrasonic vibratory method. Scanning Electron Microscope (SEM) was used to characterize these two coatings. In addition, the profilometry of the substrate and the coated surfaces was conducted to indicate the initial state of the surfaces. The obtained results from the cavitation test showed that the coating by WC-NiCr has exhibited a better performance than that of WC-CoCr coating according to the test conditions. In this regard, total weight loss of WC-NiCr coating reached to 0.66% of the original specimen weight whilst it was about 0.82% for the WC-CoCr coating. SEM micrographs of the eroded surfaces of these three materials, substrate and two coatings, have evidenced that the surface of the WC-CoCr was more damaged than the surface of the WC-NiCr coating. The HVAF thermal spraying process can be effectively used in deposition the two coatings such that improvement of steel 40 up to 2.3 and 1.8 times has been obtained by applying the WC-NiCr and WC-CoCr coatings, respectively.
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