Early damage and fatigue crack initiation at ambient and elevated temperatures in heat resistant austenitic steel

Jaroslav Polák,Veronika Mazánová,Roman Petráš,Milan Heczko,G Hénaff

doi:10.1051/matecconf/201816504008

Abstract

Fatigue damage at ambient and at elevated temperature has been studied in advanced heat resistant austenitic steel. Cylindrical specimens were subjected to constant strain rate cycling and cycling with dwell in the tensile part of the cycle with different strain amplitudes. Surface relief evolution and initiation of surface and internal cracks were studied using high resolution SEM, FIB cutting, EBSD analysis, foil preparation and STEM imaging.

Highlights

Austenitic stainless steels are employed for construction of industrial equipment in a wide range of temperatures
Recent studies at room temperature in 300 type steels [13] revealed that the cyclic strain localization is an important factor in the initiation and early growth of fatigue cracks
Cyclic plastic straining at room temperature is localized into persistent slip bands (PSBs) and repeated cyclic straining produces pronounced surface relief in the form of persistent slip markings (PSMs) at the locations where PSBs emerge on the surface [4]

Summary

Introduction

Austenitic stainless steels are employed for construction of industrial equipment in a wide range of temperatures. Due to service loads and temperature variations they are subjected to fatigue damage. The nature of the fatigue damage depends substantially on the temperature. Recent studies at room temperature in 300 type steels [13] revealed that the cyclic strain localization is an important factor in the initiation and early growth of fatigue cracks. Cyclic plastic straining at room temperature is localized into persistent slip bands (PSBs) and repeated cyclic straining produces pronounced surface relief in the form of persistent slip markings (PSMs) at the locations where PSBs emerge on the surface [4]. Intrusions represent crack-like defect from which fatigue cracks were proposed to initiate [4]. Alternative mechanism of crack initiation coming from the observations of the cracks in copper single and bicrystals [5,6] is based on the nucleation of the cracks on the grain boundary or on the PSB/matrix interface by direct condensation of vacancies

Results

Discussion

Conclusion