FIELD: chemical and heat treatment of steel. SUBSTANCE: method establishing heat stability of steel includes manufacture of samples, chemical and heat treatment of samples together with parts to obtain specified hardness with use of standard technology to form surface diffusion layer, determination of starting hardness of samples in three zones: on surface of diffusive layer, at depth of layer specified by technology and in core of sample without diffusive layer, additional heating at 500 C and repeat determination of hardness in three zones. After this loss of hardness in each zone is found as percentage of starting hardness, relative heat stability of diffusive layer in specified zone is calculated as difference of losses of hardness of core and diffusive layer referenced to losses of hardness of core and diffusive layer expressed in percentage. EFFECT: prediction of heat stability of working parts of tools made of economically alloyed steels with surface alloying and hardening which provides for increased durability of tools. 1 dwg, 2 tbl
