Materials subject to temper embrittlement?

Materials subject to temper embrittlement?

• A. Stainless Steel
• B. Nickel Alloys
• C. Low Alloy Chromes
• D. Carbon Steel

Answer: (C)

Temper embrittlement is a degradation of toughness that occurs when a metal is held at intermediate temperatures for long periods, allowing embrittling elements to diffuse to grain boundaries and weaken them. Low-alloy chromium-molybdenum steels are particularly prone to this because their grain boundary chemistry is susceptible to segregation of embrittling species during extended exposure in the tempering range. This makes their notch toughness drop even though the material remains strong. In contrast, austenitic stainless steels and many nickel alloys tend to be less susceptible to temper embrittlement under the same conditions, and carbon steels are not the classic example of this phenomenon. The practical takeaway is to avoid long exposures in the tempering temperature window for Cr-Mo low-alloy steels or to select materials and heat treatments designed to minimize boundary segregation.

Temper embrittlement is a degradation of toughness that occurs when a metal is held at intermediate temperatures for long periods, allowing embrittling elements to diffuse to grain boundaries and weaken them. Low-alloy chromium-molybdenum steels are particularly prone to this because their grain boundary chemistry is susceptible to segregation of embrittling species during extended exposure in the tempering range. This makes their notch toughness drop even though the material remains strong. In contrast, austenitic stainless steels and many nickel alloys tend to be less susceptible to temper embrittlement under the same conditions, and carbon steels are not the classic example of this phenomenon. The practical takeaway is to avoid long exposures in the tempering temperature window for Cr-Mo low-alloy steels or to select materials and heat treatments designed to minimize boundary segregation.