Method for Quantitative Evaluation of Carbon and Carbide Loss during HVOF Spraying of Cr₃C₂-NiCr Coating

For high velocity oxy-fuel (HVOF) sprayed Cr₃C₂-NiCr coating, an experimental method to evaluate the carbon and carbide loss of the particles in the stages of both in-flight and impacting on a substrate was proposed. The carbon loss in these two stages was determined by comparing the carbon content in the starting powder, the collected powder sprayed into water and the coating deposited on the substrate. The carbide loss caused by carbide rebounding, dissolving into NiCr matrix and oxidizing in-flight can be determined by evaluating quantitatively the carbide content of the collected powder and the deposited coating. According to the experimental results, it was revealed that the rebounding off of large carbides during particle impact on the substrate is mainly responsible for the carbon loss. The carbide rebounding off and dissolving are two main reasons for the carbide reduction in the coating. The carbon and carbide loss caused by oxidizing during the in-flight of particles is very limited.