Evaluation of solid particle erosion and electrochemical corrosion of plasma-sprayed WC/8YSZ coating on SS316

Abstract

Plasma spray coating enhances the corrosion and wear resistance of the stainless steel structures installed in marine applications. Hence, it is imperative to study the effectiveness of various coating combinations on the material's performance. The present work investigates the effects of three different plasma-sprayed coatings on the wear and corrosive resistance of austenitic stainless steel (SS316). The three compositions of the coating were prepared using (i) Tungsten carbide (WC), (ii) 8 wt. % Yttria Stabilized Zirconia (8YSZ), and (iii) 50 wt. % Tungsten carbide (WC) with 50 wt. % Yttria Stabilized Zirconia (8YSZ). Experiments were conducted as per ASTM G76 to determine the erosive wear with a mixture of high-velocity air and Al2O3 abrasive particles. The corrosive medium used in the electrochemical polarisation tests was 3.5 wt.% NaCl. A scanning electron microscope (SEM) was used to examine the surface morphology of the eroded and corroded coatings. Energy Dispersive X-ray Analysis (EDAX) and X Ray Diffractrometry (XRD) analysis were carried out to reveal the phase composition, elemental distribution, and lattice parameters of uncoated and coated samples. The study reveals that the composite coating (WC+8YSZ) have superior wear resistance when exposed to a high-velocity erodent. Due to the robust particle adhesion and cohesiveness of the (WC + 8YSZ) composite coating, crack initiation and propagation are rarely found on the surface of the composite coating, as evidenced by the surface wear morphology analysis. Further investigation reveals that the 8YSZ coating has excellent corrosion resistance. The SEM-based corrosive wear topography analysis reveals that the 8YSZ phase on the coated surface acts as a diffusion barrier to the electrolytic medium and a passive protective layer over the coating. Consequently, the micro-chipping of particles during exposure to the corrosive medium is prevented.

Surface morphology studies and corrosion behaviour of plasma sprayed Cr3C2/8YSZ composite coating on SS316

“…In the coated image, incomplete melting particles are discernible. EDAX analysis reveals the presence of Y, Zr, O, C, Ni, and Cr in the coating, as shown in figure 11(b) [41]. The porosity is measured to be the value of 1.91% area.…”

“…The powders were applied to the substrate as coatings with the necessary range, balance, and consistent process parameters adjusted for each coating. When modifying the powder feed rate, the relative densities of the various powders were considered [34,41].…”