Filler metal composition and method for overlaying low NOx power boiler tubes

Abstract

An alloy for use as a welding overlay for boiler tubes in a low NOx coal-fired boiler comprising in % by weight: 36 to 43% Cr, 0.2 to 5.0% Fe, 0-2.0% Nb, 0-1% Mo, 0.3 to 1% Ti, 0.5 to 2% Al, 0.005 to 0.05% C, 0.005 to 0.020% (Mg+Ca), 0-1% Mn, 0-0.5% Si, less than 0.01% S, balance substantially Ni and trace additions and impurities. The alloy provides exceptional coal ash corrosion resistance in low partial pressures of oxygen. The alloy also increases in hardness and in thermal conductivity at service temperature over time. The increased hardness improves erosion resistance of the tubes while the increased thermal conductivity improves the thermal efficiency of the boiler and its power generation capabilities.

Dependencies are inferred from the claim text.