High Chrome A49 Alloy
High chrome A49 is essentially a high chromium-low carbon white cast iron. The microstructure (shown in Figure 1(b)) is hypoeutectic and consists of eutectic chromium carbides in an austenite/martensite matrix.
The carbon content in High chrome A49 is lower than High chrome A05 resulting in less chromium in the carbide phase and more chromium in the matrix. Thus the ferrous matrix of High chrome A49 is richer in dissolved chromium than the ferrous matrix of High chrome A05. As a consequence, High chrome A49 offers greater corrosion resistance than High chrome A05 in mildly acidic environments.
High chrome A49 alloy finds use in moderately corrosive conditions where erosion resistance is also important such as some Flue Gas Desulphurisation (FGD) applications.
Typical erosion and corrosion test results for High chrome alloys
High chrome A49 is designed for slurries containing weak sulphuric acid and/or nitric acid solutions. The most widespread use is in FGD applications with chloride levels up to 50,000 ppm depending on pH. Other applications include mine dewatering where dissolved salts can cause severe corrosion. Solids concentrations are generally less than 20% by weight.