Kytskaj L. Forming a Multilayer Coating on Niobium and Tantalum for Their Protection against Oxidation

A promising trend in protection of niobium and tantalum against oxidation in applying to their surfaces of a multilayer coating in which each layer performs a certain function and as a whole it meets the requirements set to a heat-resistant coating. For the pro duction of a diffusion part of the coating on niobium and tantalum a solid solution of VI-A group metals is used as a base metal. Regularities and the maun factors influencing the process of molybdenising and tungstenising niobium and tantalum have been studied. The process of molybdenising and tungstrnising niobium and tantalum can be internsified by means of applying activating admixtu res, in particular, I-A group metals fluorides (NaF,KF,RbF). Preliminary saturation of niobium, tantalum with molybdenum and then with boron and silicon increases the stability of boride phases, heatresistance and the life of silicide and boride-silicide coatings. Technological principles of the process of production by combined methods of a multila yer coating for the protection of niobium and tungsten against oxidation have been formulated on the basis of the investigation performed.