Microstructure and mechanical property of high velocity oxy-fuel sprayed multimodal WC-Cr3C2–Co–Y2O3 cermet coating

To investigate the effect of Cr3C2 and Y2O3 additions on cermet coatings, agglomerated and sintered multimodal WC-10Cr3C2–12Co and WC-10Cr3C2–12Co–1Y2O3 cermet powders were deposited as new type of WC-based cermet coatings on plain carbon steel substrate by high velocity oxy-fuel flame spraying. Microstructures, phases, and mechanical properties of both WC-10Cr3C2–12Co and WC-10Cr3C2–12Co–1Y2O3 coatings were examined and compared with those of WC-12Co coating. Results showed that WC-10Cr3C2–12Co and WC-10Cr3C2–12Co–1Y2O3 cermet coatings presented homogeneous microstructures with multimodal carbide particles well distributed in binder matrix, and exhibited phases similar to the feedstock without decomposed phase. However, WC-12Co coating showed the existence of some serious decomposed phases including W2C and amorphous Co3W3C. Morphologies of individual splats on WC-Co substrate clearly demonstrated liquid–solid two phase deposition behaviors of three types of powders in which carbide particles were mainly present in solid state and Co in liquid state. Furthermore, fracture toughness, elastic modulus, and wear resistance of WC-10Cr3C2–12Co and WC-10Cr3C2–12Co–1Y2O3 coatings were found to be higher than those of WC-12Co coating owing to synergistic effects of Cr3C2, Y2O3, and multimodal carbides. Surface morphologies of worn out WC-12Co, WC-10Cr3C2–12Co, and WC-10Cr3C2–12Co–1Y2O3 coatings indicated that wear mechanism mainly included gouging and peeling off.