Subscribe to our newsletter to receive the latest news and events from TWI:

Subscribe >
Skip to content

Establishing Assessment Methods for Determining Safe Service Limits of High-Temperature Materials in Extreme Environments

Project Code: 34742

Start date and planned duration: January 2022, 30 months


  • Determine safe service limits for 347H and Alloy 800, against SRC

Project Outline

High-temperature corrosion and cracking are of concern to TWI’s key clients and can occur in the oil and gas industry, particularly for refineries, as well as for concentrated solar power (CSP), nuclear fusion and fission and for carbon capture use and storage (CCUS). These industries are crucial to achieving Net-Zero targets. High-temperature failure modes can be very complicated, with contributory factors including long-term aging of materials, the particular environment to which materials are exposed, as well as loading on the component. Additionally, high temperature components have design lives of ten’s of years and there are very little data on materials behaviour over such time periods. This is particularly the case for welds and heat-affected zones (HAZs), which are likely regions of failure. 

One example of a complex high-temperature cracking and corrosion failure mode, where loading, microstructure and corrosion interact, is stress relaxation cracking (SRC). SRC is known as a failure mode that can occur over moderate service durations in stainless steels and nickel alloys, which are essentially solid solution strengthened but, nevertheless, undergo significant precipitation reactions, during elevated temperature service. Alloys that are known to have been affected include austenitic stainless steels (e.g. 304H, 316H, 321H and 347H) and nickel alloys (e.g. 800/H/HT and 617). SRC failures have occurred in the chemical and petrochemical processing industries, and the phenomenon has also affected power plants made from these materials.

This project aims to utilise a combined approach of modelling, supported by materials testing, to better understand SRC and enable safe service limits for materials operating in complicated and extreme environments to be determined. Such complexity is not just inherent to SRC, but also to a number of other failure modes, including hydrogen embrittlement, strain age cracking etc. Therefore, this project will be a test bed to demonstrate an integrity assessment pipeline, which can be utilised for other materials challenges in the future.

Industry Sectors

-      Power

-      Oil & Gas

 Benefits to Industry

  • SRC is a long standing issue associated with a significant number of industry failures. A mechanistic understanding of the failure mode has been lacking and this CRP will build on previous project work to better understand the failure mechanism, whilst also providing solutions to avoid failure.  

For more information please email: