Materials of Construction: Stainless Steel Versus Nickel Alloys

Nickel alloys have long been the default choice for demanding applications in the chemical process industries (CPI). A new grade of stainless steel offers an alternative Demanding chemical engineering applications, such as plate heat exchangers (PHEs; Figure 1), tubing, pipes and pumps, call for materials that offer exceptional performance in extremely corrosive environments. That’s why many design engineers regard nickel alloys as their “go-to” choice. A popular selection is Alloy 625 (UNS N06625). This is a nickel-chromium-molybdenum superalloy that possesses both high strength and resistance to elevated temperatures. The alloy is particularly resistant to pitting and crevice corrosion as well as to severely corrosive environments. FIGURE 1. For harsh, corrosive applications, selecting the best material of construction is important for equipment, such as heat exchanger plates[/caption] However, for all the performance benefits that nickel alloys bring, there is also a significant downside. Because as well as being expensive, nickel is subject to extremely volatile pricing. For example, current geopolitical concerns have seen nickel prices fluctuate by a factor of around three in less than a year. The strategic importance…