Analysis of the Effect of Cementation Duration on the Effective Hardened Layer Thickness and Magnetic Parameter of 18ХГТ (18KhGT) Steel after Quenching

Abstract

Highly stressed transmission parts of energy-saturated machines are made of steels subjected to carburization and subsequent hardening. A low-carbon steel product forms a strong, high-carbon surface layer with a soft and viscous core. An important parameter of the hardened layer is its effective thickness hэфф. The article studies the effect of the duration of the cementation process on hэфф of samples from 18ХГТ (18KhGT) steel used for the manufacture of gear wheels of highly loaded transmissions. The possibility of using a magnetic parameter for non-destructive testing hэфф was also investigated. The device “Magnetic Sorter MS-1” was used, which measures the gradient of the normal component of the remanent magnetization field above the point of contact of the magnet pole with the metal surface. To determine hэфф, interpolation of measurements of the distribution of microhardness HV over the layer thickness on manufactured microsections was used. HV microhardness values are converted to HRC hardness values according to the dependence recommended by the international standard. Studies have shown that hэфф of the cemented layer of 18ХГТ (18KhGT) steel after quenching linearly depends on the cementation time. There is a correlation between the hэфф of the samples studied and the readings of the MS-1 device. This is a prerequisite for the development of a non-destructive method for controlling the process of chemical heat treatment of gear wheels of transmissions of mobile machines.

Keywords

• surface hardening
• cementation
• hardness
• effective thickness of the hardened layer
• non-destructive testing
• pole magnetization