Effect of heat treatment on the wet abrasion resistance of WC-10Co4Cr coatings deposited onto stainless steel by HVOF

Abstract

In the present work, the relationship between the cavitation resistance of WC-Co based coatings and the thermal spraying parameters of the HVOF process was studied. The coatings were manufactured using DJH-2600 gun, which works with hydrogen and oxygen as combustion gases. The spraying process was automatized. Three repetitions were obtained for each projection condition to verify the experiments' repeatability. The resistance to cavitation was evaluated by the indirect test of the ASTM G-32 standard. The roughness of the coatings, its surface morphology and microstructure were studied with the aid of contact profilometer, SEM and optical microscopy. The porosity of the coatings was measured by digital image processing and the analysis of the phases present in the coating was carried out by XRD. Subsequently, the data obtained were correlated with the projection parameters to find the best spraying recipe. It was found that the total combustion flux was the parameter that had the strongest effect on every evaluated property, while the combustion ratio (RC) did not have a statistically significant effect on the levels evaluated in the experimental plan. It was possible to improve the cavitation resistance of the WC-Co based coatings using high levels of FTC and a combustion ratio close to the stoichiometric point.

Wear and corrosion behaviour of the cryogenically treated tungsten carbide coatings

“…Asl et al found that after heat treatment, the wear resistance of the coatings decreased as the heat treatment temperature increased from 650°C to 1100°C and concluded that fracture toughness of the coatings has a significant effect on the wear resistance of the coatings [15]. Gallego et al reported that heat-treatment of WC-based coatings at a lower temperature 350°C, provides better wear resistance than at a higher heat treatment temperature due to the microstructural defects related to the oxidation during heat treatment [16]. So, heat treatment should be performed in an inert environment or vacuum to reduce the chances of oxidation that leads to deterioration of the wear resistance of the coatings [2,5,13,16].…”

“…Gallego et al reported that heat-treatment of WC-based coatings at a lower temperature 350°C, provides better wear resistance than at a higher heat treatment temperature due to the microstructural defects related to the oxidation during heat treatment [16]. So, heat treatment should be performed in an inert environment or vacuum to reduce the chances of oxidation that leads to deterioration of the wear resistance of the coatings [2,5,13,16].…”

Reciprocating sliding wear behavior of the heat-treated WC-12Co coatings

“…The microstructural flaws assisted with the oxidation of the coatings deteriorate the wear resistance of the coatings heat-treated above 550 °C. 15 Above 600 °C, the oxidation rate is higher; therefore, heat treatment environments also play a significant role in altering the coating properties. Govande et al 16 heat-treated WC-Co at 750 °C in the argon and air environments, and improved hardness were observed with the coatings heattreated in the argon environment compared to that of the air environment.…”

“…The microstructural flaws assisted with the oxidation of the coatings deteriorate the wear resistance of the coatings heat-treated above 550 °C. 15 Above 600 °C, the oxidation rate is higher; therefore, heat treatment environments also play a significant role in altering the coating properties. Govande et al .…”