Coking by metal dusting of nickel-base alloys

Metal dusting of nickel and Ni-base alloys occurs by inward and internal gr owth of graphite in the metal phase, leading to extrusion and ejection of m etal particles, which catalyze carbon deposition, i.e. coking. Compared to metal dusting of iron and steels which occurs via intermediate carbide form ation and lends to much finer metal particles, coking on the Ni-base alloys is much less. This is caused by the larger size and smaller amount of meta l particles formed by metal dusting and also by the clearly smaller rates o f metal wastage on Ni-base alloys.