Diffusion forming of hard carbide layer is applied for many years, mostly in Japan (TDR- Toyota Diffusion Process) and in USA (TRD- Thermo Reactive Deposition) but not so much in Europe. Carbide layers on constructive parts and tools formed in diffusion process, especial vanadium carbide layer, have excellent tribological properties and some technical and economical advantages in comparison with carbide layers formed by CVD and PVD processes. Diffusion formed layers are thicker with very strong bond to steel substrate and are produced using significantly chipper equipment as for deposition coating. Origin process has one disadvantage: partial decarburization of steel surface beneath the carbide layer reducing hardness and loading capacity of parts surface. These disadvantage are eliminate by developed and patented duplex process introducing previous carburising to prevent decarburization and to form case hardened under layer beneath the carbide layer. New developed process should contribute to widely application of diffusion carbide coating for automotive industry. Mathematical model and program for optimisation of process is presented as well as some examples of application: extruders for medium with very abrasive particles, aluminium die casting moulds etc.

Kemijsko inženjerstvo,Metalurgija,Strojarstvo