Rolling Contact Fatigue of HVOF-SprayedHardmetal Coatings on Unhardened Substrates

The present paper provides an overview of current work on the performance of thermally sprayed hardmetal coatings in rolling contact fatigue (RCF) conditions. Four different hardmetal compositions were investigated: three WC-based coatings (the two commercially available compositions WC-17%Co and WC-(W,Cr)2C-7%Ni and the experimental composition WC-1%Cr3C2-17%Ni) and Cr3C2-25%NiCr. The roller specimens were made of the unhardened steel 16MnCr5 and were coated using a liquid fuel HVOF system. After the RCF tests the coatings were characterized by examination of metallographically prepared cross sections under an optical microscope and specimen surfaces in an SEM. The RCF tests yielded consistently higher endurable pressures for all coatings of thickness 600 μm than for the uncoated specimens made of case-hardened steel 16MnCr5. The best result was obtained for the WC-1%Cr3C2-17%Ni coating.