Microstructure and Properties of Cr₃C₂-Rich Binary Cr₃C₂-WC-Ni(Co) Hardmetal Coatings

Hardmetal coating compositions containing both WC and Cr₃C₂ are less intensively studied than WC-Co(Cr) and Cr₃C₂-NiCr. In particular, compositions with Cr₃C₂ as the main phase are relatively new in the market. In this contribution, two commercial agglomerated and sintered feedstock powders with similar compositions (42Cr₃C₂-42WC-16Ni and 45Cr₃C₂- 37WC-18NiCoCr) were studied. Both powders differ in their porosity and the melting behavior, as was found by DSC experiments. Coatings were deposited with a liquid-fueled HVOF process (JP 5220). Optimization of the spray conditions was evaluated with five different spray parameter sets. Coating microstructures and phase compositions, as well as microhardness HV_0.3 and abrasion wear resistance were less influenced by the spray parameter sets. At the same time, significant differences in deposition efficiency between the two compositions were observed, which might be related to the differences in the melting behavior of the compositions and the powder porosity. However, coating microhardness and abrasion wear resistance were similar for each of the spray parameter sets. Coating microstructure and phase composition were studied with a focus on the interaction between Cr₃C₂ and WC and will be discussed in detail.