Impact of Volume and Surface Heat Treatment on the Structure and Properties of Steel 30HGSA

The work presents the results of a comparative study of volumetric and surface heat treatment impact on the structural-phase states, hardness, and wear resistance of steel 30HGSA. Surface hardening was conducted by the electrolyte-plasma method. Bulk quenching of the samples was carried out by heating to a temperature of 900 °C, followed by cooling in water and oil, and some of the samples after quenching were annealed at a temperature of 510 °C. The structural-phase states of 30HGSA steel samples were studied by metallographic and X-ray structural analysis. There were carried out the microhardness measurements, tribological tests according to the ball-disk scheme, as well as was determined the resistance of the samples to abrasive wear. It was determined that after electrolytic-plasma hardening, fine-acicular martensite with a small content of cementite is formed on the basis of metallographic and X-ray structural analyzes, and coarse-acicular martensite is formed after volume quenching in water and oil. It was determined that the microhardness increased to 400-460 HV after volume quenching, and subsequent annealing leads to a decrease in hardness to 330-360 HV. It was revealed that the electrolyte-plasma surface hardening leads to an increase in microhardness up to 2 times due to the formation of fine-acicular martensite.