Abstract

Two kinds of cermet powders; namely WC-10Co4Cr and WC- 20CrC-7Ni; were deposited on an AISI 1040 steel substrate using a high velocity air fuel thermal spraying process (HVAF) to evaluate resistance in cavitation erosion conditions with additional electrochemical effects. The microstructure of the two HVAF WC-based coatings were observed by a scanning electron microscope (SEM); while the phase composition was analyzed using an energy-dispersive microanalysis system (EDS). The microhardness (HV0.5) of the coatings was measured. In addition; the surface topography of the eroded surface layers was observed using a 3D optical profilometer. The results reveal that the cavitation resistance of the WC-20CrC-7Ni coating was approximately 1.3 times greater than that of the WC-10Co4Cr coating. The study of the structure and surface topography allows us to identity the reasons for the differences between the cavitation resistance of two coatings: the WC-20CrC-7Ni coating has a finer grain structure and a lower pore density level. These differences; along with the presence of high Cr and Ni content in the feedstock powder of this coating (responsible for strengthening the matrix); contribute to improving cavitation resistance and reducing material loss.

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