Performance evaluation of HVOF deposited cermet coatings under dry and slurry erosion

• WC-CoCr, Cr3C2-NiCr and Al2O3 coatings were deposited on S355 steel via HVOF.
• Specimens were exposed to solid-liquid impingement and dry erosion testing.
• Wear scar analysis revealed variation in the mechanisms causing coating degradation.
• Cr3C2-NiCr exhibited the highest mass and volume loss out of all examined coatings.
• WC-CoCr specimens recorded minimal volume loss with a 64% drop in wear scar depth.

The present work reports on the examination of three High Velocity Oxy Fuel deposited coatings, Tungsten Carbide, Chromium Carbide and Aluminium Oxide, under slurry erosion and dry erosion conditions. The density and hardness of coatings produced in this manner are typically superior to other thermal spray processes, and are therefore suitable for use in corrosive and highly erosive environments. The primary aim of this investigation was to establish the total mass and volume loss from each coating under dry and slurry erosion testing conditions and compare the level of material loss following the respective testing regimes. The scope of the study incorporated the application of cathodic protection to prohibit the effects of corrosion in the case of slurry erosion testing. This approach ensured that any damage to the surface could be attributed to pure erosion, and as such, be assessed against the dry erosion test data. Subsequent examination of the resulting wear scars facilitated assessment of the level of damage caused by the impinging slurry. Results revealed variation in the level of degradation experienced by each coating type under the respective test conditions. Under both dry erosion and slurry erosion, Tungsten Carbide with a Cobalt binder proved an effective protective coating by exhibiting a reduction in material loss over other assessed coatings.