The Effect of Tempering Conditions on the Delayed Fracture Characteristics of Carburized Steels

Abstract

<div class="section abstract"><div class="htmlview paragraph">A carburizing is widely applied for many kinds of engine components for motorcycles. On the other hand, a delayed fracture phenomenon of strengthened steel materials occurred under actual usage is a serious concern. The delayed fracture characteristics of surface modified steels such as a carburized steels followed by a tempering have a difficulty being evaluated by only measuring a partial characteristic of the hardened portion due to the existence of an inhomogeneity of a microstructure and a gradient of strength. Therefore, the studies on the characteristics of the delayed fracture of the surface modified steels are not so many.</div><div class="htmlview paragraph">In this paper, the authors evaluated the delayed fracture characteristics of carburized and tempered actual components by comparing hydrogen desorption curves acquired with a thermal desorption spectroscopy using hydrogen-charged specimens with changing tempering conditions. The results from this survey indicates that the delayed fracture characteristics have a relationship with the microstructural transformation of the tempered martensite depending on the tempering conditions for the carburized steels.</div></div>