In addition to its high resistance to metal dusting, HAYNES® HR-235® alloy also withstands carburization, a degradation process which occurs at lower carbon activities and which negatively affects many metallic materials, as shown in the following chart. The test involved a gas mixture of Ar – 5% H2 – 2% C3H6 at 1800°F (982°C), with a carbon activity of 1; the test duration was 215 h.
Internal Carburization in Ar– 5% H2 – 2% C3H6 at 1800°F (982ºC)
The samples for 800HT, X, and 556® alloys experienced through thickness carburization, hence the values for these three materials would have been greater, had the samples been thicker.