Effect of corrosion on cavitation erosion behavior of HVOF sprayed cobalt-based coatings

Abstract

Cobalt-based coatings have been widely applied to provide guidance to cavitation erosion (CE) and corrosion resistance since the coatings possessing superior mechanical and anti-corrosion properties. In this study, we prepared cobalt-based alloy (Stellite 21) coating and WC-17Co coating on 1Cr18Ni9Ti by HVOF. The CE resistances were evaluated in deionized water and 3.5 wt.% NaCl solution (NaCl solution), and the anti-corrosion properties were studied using polarization tests. Results show that the WC-17Co coating had superior CE resistance than cobalt-based alloy coating in deionized water because of superior microhardness and fracture toughness characteristics. The WC-17Co coating presented much loose corrosion products (W/Co-oxides) in NaCl solution, which prone to be removed by the mechanical effect of the CE and accelerated the coating damage. On the contrary, the compact Cr oxides formed on cobalt-based alloy coating surface in NaCl solution could seal the pores, preventing to formation of erosion pits, and mitigate the damage of CE. Therefore, the cobalt-based alloy coating exhibited the best CE resistance in NaCl solution and had the potential to prevent CE in seawater.

The effect of process temperature and powder composition on microstructure and mechanical characteristics of low-pressure cold spraying aluminum-based coatings

“…The local gas temperature has a significant effect on the gas flow rate, as can be seen from equation (3). The ratio of the local gas temperature to the stagnation temperature can be represented as…”

“…There are different coating deposition methods which can be applied in order to obtain high characteristics of base material to protect it from corrosion, erosion, wear, ensure some specific properties of surfaces [3][4][5][6] or to increase the service life of parts [7]. Among all methods of thermal coating, cold spraying (CS) has a number of advantages [8], namely the absence of high temperatures, oxidation, phase transformations of coating materials and substrates, and it can be successfully used to form protective and restorative coatings on light alloy parts: magnesium [9], aluminum [10] and titanium [11].…”