Abstract
Fe-1.8 % C-Cr-Mo-W-V-Co alloys varying in 4 % and 7 % of vanadium content, 0 % and 5 % of cobalt content and 5 % of each alloying element (Cr, Mo and W) were produced by casting. The characteristics of heat treatment with these alloys quenched and tempered were investigated and their rolling contact fatigue strength was studied. The quenching temperature at which the highest matrix hardness was obtained for quenched alloys became higher as the vanadium content was increased. Tempering at about 773 K resulted in the secondary hardening of the alloys. The high vanadium alloy, which contained less plate-like or rod-like M2C carbides and more granular MC carbides, showed excellent rolling contact fatigue characteristics. Since the interface between the carbides and matrix had many defects, binding force between the carbides and matrix was small and cracks propagated along the defective interface. Cracks also passed through plate-like or rod-like brittle M2C carbides which were highly sensitive to notch effects when they intersected the carbides.
