What condition primarily leads to temper embrittlement in materials?

Temper embrittlement is primarily associated with long-term exposure of materials, particularly certain alloy steels, at elevated temperatures, such as above 650°F. At these temperatures, especially when coupled with specific alloying elements like phosphorus and other impurities, the microstructure of the material can undergo changes that promote embrittlement. This occurs because the prolonged exposure allows for the diffusion of these harmful elements, which can lead to the formation of brittle phases and significant loss of ductility in the steel.

The impact of this condition is significant in various applications, particularly in pressure vessels and piping systems where structural integrity is crucial. Understanding this relationship helps inspectors and engineers proactively manage material selection and heat treatment processes to avoid the pitfalls of temper embrittlement, ensuring the safety and longevity of pressure vessels in operation.