hardfacing

Hardfacing is a material deposition process used to extend the service life of components by applying a wear-resistant surface to a less wear-resistant substrate. The deposited layer, or weld overlay, is designed to resist abrasion, impact, erosion, and sometimes corrosion, while maintaining the strength of the underlying part.

Common hardfacing alloys include iron-, nickel-, and cobalt-based compositions, chromium carbide materials, and alloy mixtures such as Stellite-type cobalt alloys. The deposited surface typically contains hard phases (carbides or martensitic matrices) that provide high hardness and abrasion resistance, while the base metal supports toughness and heat resistance.

Hardfacing uses a variety of deposition methods. Arc welding approaches (shielded metal arc welding, gas metal arc welding, gas tungsten arc welding, and submerged arc welding) are widely used, as are high-energy techniques such as plasma transferred arc, laser cladding, electron beam, and high-velocity oxy-fuel spraying. Process steps include surface preparation, controlled deposition with multiple passes to build up the surface, heat input management to limit dilution and distortion, and post-deposition treatments when required to relieve stress or temper specific alloys.

Applications cover mining and quarry equipment, earthmoving machinery, crushers and mills, pumps and valves, and agricultural implements—any component subject to sliding or abrasive wear. Typical hardfaced layers achieve substantial hardness and wear resistance; layer thickness often ranges from fractions of a millimeter up to several millimeters, depending on service conditions and process used. Bond quality depends on compatibility, surface preparation, and dilution control.

Advantages of hardfacing include extended part life, repairability of worn components, and the ability to tailor surface properties to specific wear modes. Limitations include potential residual stresses and distortion from heat input, the need for skilled application and inspection, possible reduction of toughness at the surface if carbide content is too high, and higher initial cost compared with simple repairs.