Cavitation erosion behavior of high velocity oxy fuel (HVOF) sprayed (VC plus CuNi-Cr) based novel coatings on SS316 steel

A well-known hard material (VC) has not been explored as potential candidate for surface modifications to overcome the problem of cavitation erosion (CE) in hydro machinery components. Therefore, in this course of work, VC has been blended with a malleable and soft binder material (CuNi-Cr) in three different proportions (VC, VC + 50%CuNi-Cr, and CuNi-Cr) and coated over SS316 steel with the help of HVOF spraying system. It has been observed that with the increase in VC content in the candidate coatings, the hardness, porosity, and thickness increased. CE tests were carried out with the help of an in-house fabricated cavitation erosion apparatus as per ASTM G134 Standard. The CE resistance of SS316 steel was found to be enhanced with the application of HVOF sprayed VC and CuNi-Cr based coatings. HVOF coating prepared with 100% VC content have showed excellent wear resistive properties owing to its maximum hardness (1023 HV9.81N) and better rebounding properties due to maximum thickness and porosity. CE parameters consisting of highest velocity of jet, intermediate stand-off distance (SOD) and normal impedance were found to be dominating to produce maximum cavitation erosion. Moreover, SS316 steel have showed ductile mode of failure with signatures of material removal as overlapped CE pits and plastic deformation sites. However, the mode of failure for coatings have been changed from ductile to brittle with the increase in VC content in the coating matrix with signatures changes from plastic deformation to cracks and pores in case of CuNi-Cr and VC coatings, respectively.

Automated summary

In this study, a mixture of VC and CuNi-Cr was successfully used to enhance the cavitation erosion resistance of SS316 steel. The increase in VC content in the coatings resulted in higher hardness, porosity, and thickness, and changed the failure mode of the coatings from ductile to brittle.