Investigation of Surface Stability and Behavior of Diamalloy 2002 Hard Coatings Under High-Temperature Conditions

The high-temperature and hot corrosion behavior of Diamalloy 2002 coatings with a WC/Co–NiCrFeBSiC composite structure applied to a 316 L stainless steel surface using the atmospheric plasma spraying (APS) method was investigated. The coatings were held at 900 °C in air for 5, 25, 50, and 100 h and in a molten salt bath of Na2SO4 + V2O5 at 900 °C for 1, 3, and 5 h. SEM, EDS, and XRD analyses revealed that the oxide layer on the surface thickened with increasing temperature and corrosion duration, forming NiO, Cr2O3, and mixed metal oxides. These oxide phases created a protective barrier effect by limiting diffusion between the coating and the substrate. Despite a slight increase in porosity and minor WC dissolution under long-term oxidation conditions, the coatings maintained their structural integrity up to 900 °C, demonstrating significant resistance to high-temperature oxidation and molten salt corrosion. These results demonstrate that Diamalloy 2002 coatings provide an effective surface protection solution in abrasive and oxidizing high-temperature environments.