Which statement about molybdenum in steel is true?

Which statement about molybdenum in steel is true?

• A. It decreases high-temperature strength
• B. It increases high-temperature strength
• C. It reduces corrosion resistance
• D. It has no effect on high-temperature properties

Answer: (B)

Molybdenum strengthens steel at high temperatures by hindering dislocation motion and by forming stable carbides that slow diffusion and grain-boundary processes. This combination raises creep resistance and helps maintain strength when the material is exposed to elevated temperatures. In practice, Mo-containing steels resist deformation and long-term creep better than those without Mo, especially under sustained high-temperature loads. It also tends to improve corrosion resistance in many steels, notably stainless steels, by promoting a more protective passive film and improving pitting resistance in chloride environments. Because of these effects, the statement that molybdenum increases high-temperature strength is correct, while claims that it decreases that strength, has no effect, or reduces corrosion resistance are not generally accurate for common Mo-bearing steels.

Molybdenum strengthens steel at high temperatures by hindering dislocation motion and by forming stable carbides that slow diffusion and grain-boundary processes. This combination raises creep resistance and helps maintain strength when the material is exposed to elevated temperatures. In practice, Mo-containing steels resist deformation and long-term creep better than those without Mo, especially under sustained high-temperature loads. It also tends to improve corrosion resistance in many steels, notably stainless steels, by promoting a more protective passive film and improving pitting resistance in chloride environments. Because of these effects, the statement that molybdenum increases high-temperature strength is correct, while claims that it decreases that strength, has no effect, or reduces corrosion resistance are not generally accurate for common Mo-bearing steels.