8620 Case Hardening Steel: Properties, Composition & Applications 

AISI 8620 stands as a premier low-alloy case hardening steel, engineered for components that require exceptional surface wear resistance and robust core toughness. As a nickel-chromium-molybdenum (Ni-Cr-Mo) alloy, 8620 steel is designed for carburizing, a heat treatment process that creates an extremely hard, wear-resistant surface layer while maintaining a ductile and shock-resistant core. Its balanced composition and reliable performance make it a material of choice for demanding industrial applications where strength, durability, and machinability are critical. This guide provides a comprehensive overview of its properties, heat treatment processes, and applications. 

What Is 8620 Case Hardening Steel? 

8620 case hardening steel is a low-carbon alloy steel specifically formulated for surface hardening through carburization. It is part of the nickel-chromium-molybdenum family of steels, which are renowned for their high core strength and excellent toughness. The primary characteristic of 8620 steel is its ability to develop a hard, high-carbon "case" on its surface while the low-carbon "core" remains relatively soft and ductile. 

This dual-property structure is what makes 8620 steel highly valuable. The hard exterior provides superior resistance to wear, abrasion, and fatigue, while the tough interior absorbs shock and prevents catastrophic failure under load. Its excellent response to carburizing and other heat treatments allows manufacturers to achieve precise hardness levels and case depths, making it one of the most widely used carburizing steels in engineering. Compared to other carburizing grades, 8620 offers a reliable balance of cost, machinability, and performance.