hardface

Hardfacing deposits a layer of harder, more wear-resistant material onto the surface of a base metal component by welding. The base metal is typically mild steel or ductile iron; the hardface material may be a high-carbon steel, cobalt alloy, tungsten carbide composite, or ceramic particle suspension, chosen to resist abrasion, impact, or corrosion in service. The overlay is usually 1/8 to 3/8 inch thick, built up in multiple passes if needed.

The process is economical because it preserves the toughness and machinability of the base metal while adding a surface that can withstand conditions that would destroy unprotected steel. Equipment like excavator bucket teeth, dredge pump impellers, mill rolls, and wear plates on dump truck beds are routinely hardfaced to extend service life by months or years. Rather than replace a whole component, a worn part can be built back up and re-hardened where it matters.

Technique and metallurgy

Stick (SMAW), wire (GMAW/FCAW), and submerged arc (SAW) processes can hardface, though the choice of process depends on accessibility, required hardness, and base metal thickness. Stick and wire are common in field repairs and small shops. The deposited metal must bond metallurgically with the base, not merely sit on top, so proper preheat, interpass temperature control, and cleaning between passes are critical. If cooling is too fast, the heat-affected zone becomes brittle and cracks; if too slow, the hardness may soften.

Tungsten carbide hardfacing, often applied with oxyacetylene or plasma spray methods, gives the highest wear resistance but is brittle and expensive. Martensitic stainless and cobalt alloys offer a middle ground: good hardness (typically 40 to 65 HRC), toughness, and lower cost. The choice depends on whether the part faces sliding wear, impact, thermal shock, or corrosion.

The name reflects the job itself: you are facing the metal with a harder material. In older usage, hardfacing sometimes referred to flame-hardening as well, but in modern welding terminology it denotes overlay deposition specifically. The term is universal in fabrication, repair shops, and heavy equipment maintenance.