Chrome Molybdenum Steel and High Temperature Applications

Chromium-Molybdenum Alloy Steel (or Chromium-Molybdenum), is an alloy used for high pressure and high temperature applications. It is used in the oil and gas, energy, construction and automotive industries due to its corrosion resistance, high temperature and tensile strength.
Chromium-molybdenum steel-often referred to simply as chrome-molybdenum steel-is a low-alloy steel used in many applications and industries. As the name suggests, two key alloying elements are molybdenum (Mo) and chromium (Cr). These alloys are usually grouped into one main category, and the common names are Chromium Chromium, Chromium Alloy, Molybdenum, and CrMo [1].
Why choose Cr and Mo?
Mo has been a standard alloying element for many years in the production of creep-resistant steels capable of withstanding temperatures up to 530 °C [2]. This is because Mo successfully reduces the creep rate of the steel and also slows down the agglomeration and coarsening of carbides during high temperature use. Furthermore, this high temperature adaptability and creep resistance mean that the main applications for molybdenum-based steels are in power generation and petrochemical plants.
What makes these two alloying elements so effective is their combined properties (minimum 9% Cr and 1% Mo [4]). For example, molybdenum gives steel a higher working temperature and increased strength. In addition, Cr causes abnormal oxidation and helps steel resist corrosion in a more efficient manner [1]. Cr also provides good hardness penetration, and Mo content ensures uniform hardness [3].
This increased strength and corrosion resistance explains the fact that CrMo steel is used when the strength provided by mild steel is not sufficient. These benefits provide added reliability of chrome molybdenum, which is why it is used in so many different applications.