Effect of Microstructure and Hardness on Cavitation Erosion and Dry Sliding Wear of HVOF Deposited CoNiCrAlY, NiCoCrAlY and NiCrMoNbTa Coatings

Abstract

Metallic coatings based on cobalt and nickel are promising for elongating the life span of machine components operated in harsh environments. However, reports regarding the ambient temperature tribological performance and cavitation erosion resistance of popular MCrAlY (where M = Co, Ni or Co/Ni) and NiCrMoNbTa coatings are scant. This study comparatively investigates the effects of microstructure and hardness of HVOF deposited CoNiCrAlY, NiCoCrAlY and NiCrMoNbTa coatings on tribological and cavitation erosion performance. The cavitation erosion test was conducted using the vibratory method following the ASTM G32 standard. The tribological examination was done using a ball-on-disc tribometer. Analysis of the chemical composition, microstructure, phase composition and hardness reveal the dry sliding wear and cavitation erosion mechanisms. Coatings present increasing resistance to both sliding wear and cavitation erosion in the following order: NiCoCrAlY < CoNiCrAlY < NiCrMoNbTa. The tribological behaviour of coatings relies on abrasive grooving and oxidation of the wear products. In the case of NiCrMoNbTa coatings, abrasion is followed by the severe adhesive smearing of oxidised wear products which end in the lowest coefficient of friction and wear rate. Cavitation erosion is initiated at microstructure discontinuities and ends with severe surface pitting. CoNiCrAlY and NiCoCrAlY coatings present semi brittle behavior, whereas NiCrMoNbTa presents ductile mode and lesser surface pitting, which improves its anti-cavitation performance. The differences in microstructure of investigated coatings affect the wear and cavitation erosion performance more than the hardness itself.

Effects of Shot Peening and Cavitation Peening on Properties of Surface Layer of Metallic Materials—A Short Review

“…The test rigs employed for cavitation erosion testing primarily utilise hydrodynamic and vibratory cavitation. Vibratory cavitation erosion resistance tests are mainly conducted under ASTM G32 standard recommendations [ 97 , 98 , 99 ], while hydrodynamic cavitation test rigs usually conform to ASTM G134 standard (cavitating liquid jet) or are not-standard solutions, such as rotation discs or cavitation tunnel rigs [ 100 , 101 , 102 ]. Therefore, optimising the cavitation peening process parameters is necessary to prevent the surface from the erosive action of cavitation and obtain the required peening effects.…”

The Concept of WC-CrC-Ni Plasma-Sprayed Coating with the Addition of YSZ Nanopowder for Cylinder Liner Applications

“…The microstructural and geometrical measurement of the wear area formed during the friction test requires a deeper analysis using microscopic methods. In further research, the other wear tests for the developed coating such as cavitation [ 60 , 61 ] and ball-on disc [ 62 ] might be conducted.…”

Effect of Initial Surface Scratches on the Cavitation Erosion Behavior of 316L Stainless Steel Substrates and 316L Stainless Steel Coatings

“…For the coating specimens, the difference in the erosion rate was mainly observed at the initial stage of the cavitation erosion process ( Figure 4 b). Generally, materials with higher hardness are more resistant to cavitation erosion [ 26 , 27 , 28 ]. Despite the higher average microhardness of the ground coating than that of the coating sample, no significant difference was observed between them ( Figure 3 b).…”