Sintered hard metals

The object of the method described is to increase the hardness of sintered metallic products without changing their composition and without causing any appreciable reduction in strength. It is applied here to carbides of W, Ti, Ta, Nb, Cr, and V with binders of Co or other metals or combination of metals of the Fe group. The object is achieved by irradiation of the product. It is found that the degree of hardness and the depth of hardening depend on the type of radiation and the dose, the heavier particles and the larger the dose the greater the effect. The product may be cooled during irradiation in order to keep it below a temperature at which annealing takes place, and irradiation may be effected in vacuum or inert atmosphere to avoid oxidation. Irradiation with β-rays, protons and 3He+ ions has been used with success, but if a greater depth is required hardening by the fast electrons from an accelerator is preferable. (U.K.)