Investigating the NiAlCr composite coatings applied on steel substrate of st37, using the HVOF method

Al-Cr intermetallic compounds of Nickel-Aluminum and chromium (Ni-Al-Cr) being a well-known coating for the engineers and industrial designers due their unique properties such as increasing the wear resistance and increasing the corrosion and oxidation resistivity in this study, the morphology and wear behavior of Ni-Al-Cr composite coatings, applied on steel substrate by high velocity oxygen fuel (HVOF) thermal spraying are investigated. For this purpose, aluminum, chromium and nickel powder were used with the stoichiometric ratio of Al50Cr25Ni25. used and after the mechanical alloying process for 50 hours, the powder was applied using the HVOF process on the steel substrate. The microstructural analysis of the samples were investigate via the X-ray diffraction analysis (XRD) and scanning electron microscope (SEM). Results showed that after 50 hours of mechanical alloying process, intermetallic compound of (NiAl) Cr were formed with the crystal size of 10 nm. It was also clarified that after the HVOF process, the grain size of coating is less than 30 nm. The results show that by applying composite coatings, hardness and wear resistance of the samples were increased for 3 and 4 times respectively as compared with conventional coatings. The predominant wear mechanisms were a combination of adhesive, abrasion and scratching with the friction coefficient of about 0.2.