The main disadvantage of Monel is its cost. As a group of nickel-based alloys built on up to 67% nickel, Monel relies heavily on one of the most expensive elements used in corrosion-resistant metals, and one whose price can be volatile.
For some applications, super duplex stainless steels can substitute for Monel, offering similar strength at far lower cost with good corrosion resistance in seawater and many acids. Their operating temperature range is more limited, however: below -50degC or above 250degC, they may not be a suitable alternative.
So-called super austenitic stainless steels, such as Alloy 254, can match the low-temperature range of Monel but offer far lower strength. High-strength stainless steels such as Nit50 can match both the strength and the low-temperature range, but without Monel's level of corrosion resistance.
Although stainless steels and some nickel-based grades such as Alloy 825 offer significant cost savings, they cannot match Monel across the full low and high temperature range, or in the most aggressive environments found in chemical processing, oil and gas, and marine applications.
We stock Alloy K-500 as round bar from 5/8"-10" diameter (15.87-254mm).