Hardfacing Weld Overlays That Extend Service Life

Hardfacing (also called weld overlay) is a high-temperature welding process that applies a wear-resistant alloy directly onto a base material. Unlike thermal spray, hardfacing creates a metallurgical bond between the overlay and the substrate, resulting in a homogeneous, fused layer that becomes part of the component. Hardfacing extends equipment life by restoring worn parts to OEM dimensions, protecting new components in wear zones, and resisting abrasion, erosion, corrosion, heat, and impact in severe-duty environments.

Delamination is the separation or loss of bond between a weld overlay and the base material. It might be a process control problem rather than a material problem. Possible causes include improper preheat and interpass temperatures, unmanaged dilution, missing transition or butter layers, and inconsistent post-weld cooling or heat treatment. When these parameters are controlled through documented weld procedures, hardfacing delivers multi-year service life without delamination.

When engineered and applied correctly, hardfacing can deliver multi-year service life in demanding environments. HFW's hardfacing solutions have operated for five or more years on high-temperature valve components in power generation service without delamination. Actual service life depends on the alloy selection, the base material, the operating environment, and the discipline of the weld procedure.

Hardfacing creates a metallurgical bond by welding the overlay material into the base at high temperature, with controlled dilution into the substrate. Thermal spray creates a mechanical bond at much lower temperatures (typically below 300°F) with no melting of the base metal. Hardfacing is preferred for high-heat, high-load, structural, and severe-abrasion applications. Thermal spray is preferred for tight tolerances, fine finishes, and parts that cannot be distorted. HFW offers both so engineers can match the process to the part.

HFW applies nickel-based alloys, cobalt-based alloys including Stellite®, iron-based buildup alloys, carbide-reinforced systems, and specialty alloys for high heat, corrosion, impact, or chemical attack. Materials are supplied in rod, wire, or powder form depending on the welding process. The right material is selected based on the wear mode, operating temperature, chemistry, and finish requirements of the specific application.

Overlay thickness depends on the process, the alloy, and the base material. PTA, TIG, and MIG can deposit thicker overlays than thermal spray, and multiple passes with proper interpass temperature control allow substantial build-up. HFW's weld procedures specify pass sequencing, filler metal size, and finishing methods to achieve the final thickness and tolerance the application requires.