Abstract
Austempering, which produces a bainitic microstructure, is widely recognized as the preferred heat treatment when toughness is the primary requirement for a component. The literature contains numerous studies comparing the mechanical properties of tempered martensite with bainite of equivalent hardness. The majority of these findings demonstrate superior properties in bainitic microstructures. Bainite exists in two forms: upper bainite, which forms during isothermal transformation at higher temperatures (typically around 500 °C), and lower bainite, which develops at lower temperatures (approximately 350 °C, depending on the specific alloy steel). Lower bainite exhibits hardness values similar to tempered martensite and is preferred in applications where elastic characteristics are desired.
