THE EFFECT OF CARBON CONTENT ON THE MARTENSITE START TEMPERATURE IN NICKEL-ALLOYED STEELS

Retained austenite is a very important structural component, especially in high-alloy and high-carbon steels. With certain alloying and heat treatment, its amount can be up to 95−98%. Therefore, it is essential to determine the start temperature of the martensitic transformation (martensite point) depending on the chemical composition. At present, there is no definite expression for this dependence. Researchers use numerous calculation models and experimental data. In this paper, the dependence of the martensite point on the carbon content in steels alloyed with a non-carbide-forming element — nickel — is considered. The work uses a structural method for determining the martensite point using a high-temperature metallographic unit. Actually, nickel has the greatest effect on the martensite point in low-carbon steels. With an increase in the carbon content, the effect of nickel weakens, and for steel 143N4, the martensite point is even higher than in carbon steel with a similar carbon content. It was found that at high carbon content, even while rapid cooling, graphitization occurs. It should be considered the reason for the increase in the martensite point. The materials of the article were presented at the International Scientific and Practical Conference «Advanced Engineering Technologies (AET 2024)» held in St. Petersburg on May 13−16, 2024.