API 571 Certification (Corrosion & Materials) Practice Test

What material is particularly vulnerable to embrittlement in high temperature applications?

1. Duplex stainless steel

2. 300 series stainless steel

3. 400 series stainless steel

4. Nickel alloys

The correct answer is: 400 series stainless steel

The material that is particularly vulnerable to embrittlement in high-temperature applications is the 400 series stainless steel. This type of stainless steel is primarily made up of martensitic and ferritic structures which can become susceptible to embrittlement at elevated temperatures due to processes such as temper embrittlement and, in some cases, the formation of detrimental microstructures like sigma phase or chromium carbides. In high-temperature environments, the 400 series can undergo changes that negatively affect its mechanical properties, especially its toughness. This is particularly evident when prolonged exposure leads to the precipitation of carbides or intermetallic compounds. Such changes can cause a reduction in ductility and an increase in brittleness, which can be critical in applications where mechanical integrity is paramount. By contrast, duplex stainless steels, 300 series stainless steels, and nickel alloys typically maintain better performance in high-temperature environments, as they are designed with more favorable microstructural characteristics and compositions meant to resist the types of degradation that lead to embrittlement.