ABSTRACT
Calorising is a high-temperature diffusion process using a blend of ferro aluminium, Al2O3, NH4Cl and a number of other alloys. The process creates an Al-rich outer layer which increases the surface hardness of the component (600-650 Brinnel hardness number, BHN) significantly resulting in greatly improved wear resistance. At elevated temperatures, the Al2O3 surface that forms to a depth of 100-150 microns, provides an excellent hightemperature abrasion resistance. The inter-metallic layer seals the base metal improving resistance to oxidation.
