Observation of Elevated-Temperature Fatigue Surfaces for Stainless Steel with Dispersed Lead Particles by an AFM/STM Hybrid System

Fatigue threshold for SUS304 stainless steel containing 0.2 weight percent dispersed lead particles was about 40% higher for the host steel at test temperatures above 200°C. This was explained by considering that dispersed lead particles could control or arrest the fatigue crack growth. In this study, using an AFM/STM hybrid system which enables one to obtain topographic and current images at the same time, fatigue surfaces for SUS304 steel with lead particles were examined to clarify the controlling mechanisms in the fatigue crack growth. Topographic and current images showed that the oxide layer spalled at the fatigue crack tip was repaired by the molten lead at test temperatures higher than 200°C. Accordingly, we concluded that dispersed lead particles controlled the fatigue crack growth at elevated temperatures.