Official Answer
Answer
Quench and Temper (Q&T) produces a tempered martensite structure, which is hard but can be prone to micro-cracking and brittleness if not controlled. Austempering involves quenching the spring into a salt bath held just above the martensite start ($M_s$) temperature, typically around 300°C, and holding it until the austenite transforms into 'Bainite.' This acicular ferrite and cementite structure provides higher impact toughness and greater ductility for a given hardness level. For wave springs, which experience complex bending stresses, a bainitic structure reduces the sensitivity to surface notches and enhances the fatigue life, particularly in dynamic automotive clutch assemblies.
