| Worn crankshaft journals with an induction-hardened surface layer are difficult to repair by High Velocity Oxy-Fuel (HVOF) powder metal overlays. The problems occur after cladding, and results in the overlays failing at the interface with the hardened surface, since the induction hardening has a deleterious effect on the surface preparation. Conventional tempering and intercritical induction heat treatments were assessed for modifying the surface hardness of the induction-hardened steel. Both processes are effective in reducing the surface hardness in short-time cycles by tempering the martensite. In addition, the intercritical induction heat treatment is then shown to be more effective for lowering surface hardness. The coating properties of the induction heat-treated crankshaft journals are evaluated by SEM. The adhesion strength of HVOF coatings is assessed by a modified ASTM Standard C 633-01 technique. The conclusion is that the crankshaft journals with the induction-hardened surface could be remanufactured by HVOF process after a short-time induction heat treatment process. |
