A method of preparing a mechanical component with an Fe—Cr—C hardfacing weld overlay alloy for improving the resistance of the mechanical component to abrasion, erosion or erosion/corrosion for use in very abrasive, erosion or erosive/corrosive environments by significantly increasing the hardness of the weld overlay is disclosed. To improve the resistance to abrasion, erosion or corrosion, a weld overlay of a Fe—Cr—C hardfacing alloy is applied onto the surface of a metallic component, such as tubes, pipes, or vessels. Welding and cladding methods including gas-metal-arc welding (GMAW), gas-tungsten-arc welding (GTAW), and laser cladding may be utilized. Then, the component is heat-treated at elevated temperatures for a sufficient time, resulting in additional hardening and thus further increasing the weld overlay's resistance to abrasion, erosion, or erosion/corrosion.