API 571 Certification (Corrosion & Materials) Practice Test

Which material is highly resistant to carburization?

1. Cast Stainless Steel

2. 300 series Stainless Steel

3. 400 series Stainless Steel

4. Nickel Based Alloys with significant iron content

The correct answer is: Nickel Based Alloys with significant iron content

Nickel-based alloys with significant iron content are highly resistant to carburization due to their unique alloying elements and microstructure. Carburization is a process where carbon diffuses into metals, which can degrade properties like ductility, toughness, and strength. Nickel-based alloys contain a higher concentration of nickel, which enhances their overall corrosion resistance and lauds their ability to withstand high-temperature environments where carburization tends to occur. The resistance to carburization in these alloys stems from their ability to form stable protective layers and the nature of nickel's phase stability, which prevents carbon from diffusing easily into the alloy. Additionally, the presence of iron improves their mechanical properties and stability under various conditions. In contrast, other materials listed, such as cast stainless steels and both the 300 and 400 series stainless steels, lack such robust resistance to carburization. These stainless steels can be more susceptible to carbon uptake under similar conditions, compromising their integrity and performance. Thus, nickel-based alloys are preferred in applications where resistance to carburization is critical.