Molybdenum is a more effective alloying element than nickel for enhancing hardenability. The addition of molybdenum promotes response to heat treatment and increases hardness, wear resistance, and strength to the required level in applications with highly loaded PM parts such as helical gears.
It has a lower affinity for oxygen and a smaller effect on compressibility compared with nickel. Typical additions range from 0.5 to 1.5%. The addition of molybdenum promotes response to heat treatment and increases hardness, wear resistance, and strength to the required level in applications with highly loaded PM parts such as helical gears.
The figure shows the increase in hardenability with higher nickel (to 4%) and copper (to 2.25%). The effect of these alloying additions is particularly apparent in the tensile strength. Ductility is also improved significantly at all cooling rates tested.
For more information, click on the link below (subscription required). Then scroll to Figure 16.
Joseph W. Newkirk, Heat Treatment of Powder Metallurgy Steels, Heat Treating of Irons and Steels, Vol 4D, ASM Handbook, Edited By Jon L. Dossett, George E. Totten, ASM International, 2014, p 253-273, https://doi.org/10.31399/asm.hb.v04d.9781627081689.
