Heat treatment processes include gas nitriding, stress relieving, annealing, normalising, hardening and tempering, spheroidizing, carburizing, liquid-nitriding, nitro-carburising, carbo-nitriding, tufftriding, marquenching, austempering, martempering, sherardizing, manganese and zinc phosphating, special surface coatings such as ceramic and molybdenum di-sulphide for un-lubricated wear applications and induction hardening.