Slide 9 of 12
The other major problem associated with overlaying stainless steels is corrosion. Unfortunately, the weld shop or overlay shop cannot determine the extent of this problem until it has occurred in the field. However, the shop can be aware of the effects of welding parameters on the corrosion resistance of the overlay. The above shows a representation of the stainless microstructure with Austenite and Ferrite. The speckled region represents CARBIDE PRECIPITATION. This occurs when the overlay is exposed to excess heat and may be enhanced or retarded by alloy additions. 300 Series Stainless steels get their corrosion resistance from the Chromium Oxide that forms on the surface to the overlay. If the Chromium becomes married to a Carbon atom to form a Carbide, then the Chromium cannot form the needed Oxide for corrosion resistance.