On corrosion behaviour of HVOF sprayed Ni₃Si intermetallic powders

Abstract

Ni3Si intermetallic powders were deposited onto 420 stainless steel substrate using high velocity oxy-fuel (HVOF) process. In this regard, microstructure properties relationships were evaluated in fabricated coatings. X-ray diffractometery, scanning electron microscopy, microhardness testing, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) measurements were performed to study the phase composition, microstructure and properties of the coatings. The microstructure of coatings was composed of supersaturated Ni(Si) solid solution islands embedded in an Ni5Si2 matrix. The results showed that this microstructure strongly affected properties of coatings. In this regard, the hardness of coatings was found to be 620 HV(50 g) due to presence of Ni5Si2. It was also found that the corrosion rate of HVOF Ni–Si coatings in 70H2SO4 medium was lower than that of stainless steel substrate. Further investigations showed that the microgalvanic corrosion between Ni(Si) and Ni5Si2 phases was a determinant factor in corrosion performance of HVOF Ni–Si coatings.

Microstructure and corrosion behaviour of laser-cladded γ-Ni/Mo2Ni3Si alloy coating

“…Thus, the materials used for the key mechanical parts should possess excellent wear and corrosion resistance to withstand the harsh service environment [3][4][5]. As a significant branch of intermetallic compounds, the metal silicide exhibits a good performance on hardness, high temperature strength and chemical stability, showing potential to be used as anti-wear and corrosion-resistant materials in engineering applications [6][7][8]. However, its serious brittleness (especially at room temperature) is a major obstacle to engineering applications.…”