Innovative coating for Electroplated Hard Chromium replacement in severe environments

The aim of this paper is the study and the characterization of new solutions for the replacement of Electroplated Hard Chromium (EHC) coatings in severe environments. Starting from the failure analysis of hard chromium at high temperature and subjected to severe wear conditions, the phenomena and mechanisms leading to coating failure were investigated and understood. From this preliminary analysis the coating main properties were identified and innovative solutions were considered and studied to check their suitability for the application.Finally, the characterization of the proposed solution was compared to the properties and the failure mechanism of similar type of coatings used in the same environmental conditions.The innovative solutions considered in this paper are electroplated double layer nickel chromium and ceramic coatings obtained by thermal spraying with different techniques, specifically a tungsten carbide in cobalt or cobalt chromium matrix by High Velocity Oxygen Fuel ( HVOF) and High Velocity Air Fuel techniques (HVAF).