DETERMINATION OF THE EFFECTIVE THICKNESS OF HARDENED LAYER OF CARBURIZED GEARS

Abstract

The methods are considered for determining the effective thickness of the hardened layer of metal parts listed in the standards STB 2307-2013 and STB ISO 18203-2019. The ambiguity of interpretation of the concept of effective thickness hэф of the hardened layer up to the half-transition zone is established for control of gears after the chemical heat treatment: carburizing and hardening. In practice, hэф is determined by the Vickers hardness distribution under the relevant load. In accordance with the standard ASTM E140-07, the Vickers hardness value of 50 HRC represents the Vickers hardness of 513 HV for non-austenitic structural steels when tested at 294.2 N. When testing Vickers hardness at lower loads, conversion tables or dependencies must be used. It has been shown that such measurements are more inaccurate at lower loads. To eliminate errors and increase accuracy of determining hэф of diffusion thickness of gear wheels after chemical-hardening, techniques are compared to determine hэф three: metallographic, mechanical and chemical. The Vickers hardness values determined during tests of structural non-austenitic steels with different loads correspond to the hardness value of 50 HRC. The values obtained can be applied to determine hэф of diffusion layers of surface-hardened parts corresponding to the half-transition zone.