Mechanistic evaluation of high velocity air fuel (HVAF) WC-10Co4Cr flash coatings for erosion-corrosion protection of downhole drilling rotors

Electrolytic hard chrome (EHC) coatings have long been the standard for protecting downhole drilling components from extreme wear and corrosion. However, concerns over toxicity, regulatory compliance, and microcrack-induced degradation in hard chrome coatings have created a need for more sustainable alternatives. High velocity air fuel (HVAF) WC-10Co4Cr flash carbide coatings have emerged as a leading candidate, but their long-term performance and degradation under service conditions remain unexplored. This study evaluates the performance of HVAF flash carbide coatings and conventional hard chrome across three representative conditions: static corrosion, pure erosion, and combined erosion-corrosion. Long-term exposure tests were conducted, and the degradation behaviour of both coatings was evaluated through mass loss and microstructural characterization. The results show that while both coatings perform comparably under pure erosion condition, the flash carbide coating offers significantly higher resistance in both corrosive and erosion-corrosion environments. By providing insights into the mechanisms of material degradation in these environments, the work demonstrates the suitability of flash carbide as protective coating for extending the service life of downhole infrastructure.