Metal dusting II - Corrosion defects

Metal dusting II - Corrosion defects

Figure 1: Furnace chain severely attacked by metal dusting. This is an application where RA333 has given the best service life in original equipment.

Defect name: No data.
Record No.: 2387
Type of defect (Internal/Surface): Surface
Defect classification: Corrosion defects
Steel name: Steel
Steel composition in weight %: No data.
Note: A somewhat aggravating problem in carburizing atmospheres is “metal dusting”, a.k.a. “catastrophic carburization”, or “carbon rot”. This occurs at lower temperatures, typically 800—1200°F (430—650°C) in heat treating furnaces. Such temperatures exist in a carburizing furnace (nominal 1750°F/950°C) where alloy tube hangers, atmosphere sampling tubes or electrical leads pass through furnace walls, and in some areas of Ipsen furnace chains. The exact mechanism may be disputed, but the effect is that the metal disappears. A bar may look just like a beaver had chewed away on it. In other cases, the metal literally appears worm-eaten on the surface. In the petrochemical industry, a small amount of sulphur (40—50 ppm H2S) is sometimes added to the process gas stream to “poison” the high temperature chemical reaction that is metal dusting.
Reference: Not shown in this demonstration version.