What is better than INCONEL?

‍Inconel

Inconel is a class of nickel-chromium-based superalloys with high corrosion resistance, oxidation resistance, high-temperature strength, and creep resistance. Inconel is able to withstand high temperatures and extremely corrosive environments due to two factors.

First, the intermetallic compound Ni3Nb is formed in the gamma bis(ɣ’’) phase. This intermetallic phase acts as the "glue" on the grain boundaries. This "glue" prevents the grains from growing in size when heated to high temperatures (in most cases, smaller grains mean greater strength, larger grains mean greater ductility). Secondly, Inconel is highly resistant to corrosion due to the passivation layer formed when heated. These two factors make Inconel an ideal alloy for applications ranging from hot-section gas turbines to deep-sea drilling. So what are the disadvantages of these alloys? They are expensive, difficult to work with and difficult to process.

Stainless steel

Stainless steel is characterized by a chromium content greater than 10.5% by weight. There are five categories of stainless steel:

austenite
ferrite
martensite
duplex
precipitation hardening

These stainless steels are named after the microstructure formed in these alloys. Duplex stainless steels are a mixture of austenitic and ferritic microstructures, and precipitation hardening means that precipitates can form to increase the strength of this type of stainless steel. The strength and corrosion resistance of stainless steel depend on these microstructures. For example, austenitic stainless steels will be the most ductile stainless steel category, but also the most corrosion-resistant. On the other hand, the martensite type generally has higher strength but less corrosion resistance. Austenitic stainless steel has a larger equiaxed grain structure compared to the smaller lathe structure in martensitic stainless steel, which gives it these properties.

All stainless steels have higher corrosion resistance than traditional steel and are used in everything from kitchenware and structural building applications to biomedical and food preparation applications.

Inconel vs. Stainless Steel: What’s the Difference?

For one thing, Inconel is much more expensive than stainless steel alloys. Inconel also has better corrosion resistance and strength at high temperatures. However, steels such as 17-4PH stainless steel are stronger than Inconel at lower temperatures. When choosing between two different alloys, the main deciding factors are cost, temperature and strength. If a lower-cost but relatively strong component is required, stainless steel may be the best choice. If air critical components require high temperatures, then Inconel is a better alloy for the application.