Hardfacing

The cost of replacing components which become worn or damaged during service has led to the development of a wide range of techniques known as “hardfacing”, which can restore the parts to a reusable condition. Many such repairs have a longer life than the original component because it is possible to deposit coatings more resistant to wear, impact, abrasion or corrosion than the original material. As a result, hardfacing is now widely used on many production components.

Abrasion-resistant alloy has poor impact properties.  Conversely, impact resistant alloys have poor abrasion resistance.  The higher an alloy's abrasion resistance, the lower its ability to withstand impact, and vice versa.  Between these two extremes are numerous wear facing alloys that combine varying degrees of resistance to abrasion with the ability to absorb a fair amount of impact.  The selection of wear facing alloy for a certain application is determined by the requirements of its anticipated service.

Preheating of base metal is sometimes necessary to minimize distortion, to prevent spalling or cracking to avoid thermal shock.  Preheat temperature is influenced by two important factors the carbon content and alloy content of the base metal

There are considerable differences exist between welding materials used to build-up worn equipment / parts and those used for hardfacing overlays.

The common types of wear are Abrasion, Heat, Impact, and Corrosion.  Abrasion is the grinding action caused by abrasive solid sliding, rolling or rubbing against a surface.  Referred to as gouging - when combined with high compressive loads.  Impact refers to a blow or series of blows to a surface, resulting in fracture or gradual deterioration.  Heat softens metallic structures and may accelerate chemical attacks like oxidation and scaling; however it may cause changes that increase hardness and brittleness.  Lastly, Corrosion - The deterioration of metal by chemical or electrochemical reaction with its environment.

Cleaning all areas to be hardfaced with a grinding helps eliminate pin holes and makes easier to apply the hard metal.