Session: MF-24-04 Materials and Fabrication for Refining - 4

Paper Number: 107793

107793 - Stress Relaxation Cracking, A Misunderstood Problem in the Process Industry 

Stress Relaxation Cracking (SRC), also known as reheat cracking (RC) or stress relief cracking, is a high temperature failure mechanism known to occur in austenitic and ferritic creep resistant steels and nickel base alloys. Many root causes have been described in the literature, ranging from grain boundary oxidation to stress relaxation localization and creep ductility exhaustion. Long has it been assumed that SRC/RC is triggered by microstructural degradation, and hence, it was thought that some alloys might be immune. However, research during the last 25 years has conclusively demonstrated that any alloy can succumb to this failure mechanism as it is a creep damage mechanism.

SRC/RC can occur during service in long-term, high-temperature exposure or during fabrication in a stress relief heat treatment. A comprehensive understanding of the causal mechanisms will explain the risk in both cases and can help predicting and preventing these risks. In this paper, the various mechanisms active in relaxation cracking will be separated from those that are not. Some often-quoted characteristics of SRC/RC will need to be acknowledged as non-causal, and circumstantial only. Finally, the reader will be pointed to an empirical modeling procedure that is being used in the nuclear power industry in the UK. This procedure is able to accurately predict the occurrence of SRC/RC in service based on lab characterization of alloys and FEA stress analysis.

Presenting Author: Jan-Willem Rensman Fluor BV

Presenting Author Biography: Jan-Willem is a Welding and Metallurgy Fellow at Fluor. He holds a master’s degree in Mechanical Engineering from the Technical University of Twente in the Netherlands. He graduated with honors from the Utrecht University of Applied Sciences to become a registered International Welding Engineer. Jan-Willem has authored and co-authored more than 30 articles in peer-reviewed journals.
Jan-Willem joined Fluor in 2007 after 10 years in materials research. He focuses on materials performance during fabrication and service, and is therefore interested in materials degradation mechanisms and embrittlement. He has performed failure root cause analyses in the nuclear, construction, and refining industries.

Authors:

Jan-Willem Rensman Fluor BV
Mike W. Spindler EDF Energy
Cathleen Shargay Fluor Corporation