Study of Cavitation Erosion-Corrosion Resistance of Thermally Sprayed Ni-Based Coatings Prepared by HVAF Process

Abstract

In this study, two Ni-based coating materials, namely NiCrMoNb and NiCrBSi, have been applied using High Velocity Air Fuel (HVAF) thermal spraying process. The performance of the coated surface in resistance to cavitation erosion-corrosion of both coating materials, has been evaluated using an ultrasonic vibratory method. The cumulative material loss and erosion rate curves of the two coatings have been discussed. Surface topography, microhardness, macroscopic images, and scanning electron microscope (SEM) micrographs were used to characterize the coatings before and after the cavitation test. The cavitation results showed that the NiCrMoNb coating surface has exhibited better performance than the NiCrBSi coating surface under the same test conditions. The total cumulative weight loss of the NiCrMoNb coating was about 1/3 that of the NiCrBSi coating. SEM micrographs of the eroded surfaces showed that the surface layer of the NiCrBSi coating was more damaged, compared to layer of the NiCrMoNb coating. Overall, the NiCrMoNb coating can be effectively used against the cavitation wear, due to its superior performance.

High-velocity air fuel coatings for steel for erosion-resistant applications

“…The cavitation erosion resistance of HVAFsprayed 86WC-10Co4Cr [18], WC-10Co4Cr, WC-CoCr [10], Cr3C2-25NiCr [34], FeCrMnSiNi, FeCrMnSiB [35], Cr3C2-50NiCrMoNb, Cr3C2-25NiCr, and Cr3C2-37WC-18NiCoCr [36] coatings were superior to HVOF-coatings due to their lower porosity, higher hardness, higher toughness [18], and lower oxides content [35]. HVAF-sprayed NiCrMoNb coatings also exhibited promising cavitation resistance due to superior microstructural and mechanical features [37]. Varis et al [10] proposed that high compressive stresses of HVAF-coatings inhibit the fatigue crack formation and propagation along the microstructure consisting of lamellae interfaces, thus improving the cavitation resistance of the coating.…”

Cavitation Resistance of Coatings with a Metastable Austenite Structure

“…Employing a new working principle developed by the authors of [11,32], an ultrasonic vibratory tester was used to evaluate the cavitation erosion of the specimens. Figure 2 schematically describes the cavitation test arrangement.…”