It is commonly used for surface repair and functional enhancement of mechanical equipment, particularly in mining machinery, metallurgical equipment, construction machinery, agricultural machinery, and the energy industry.

Metallurgical bonding is the core of hardfacing

Principle analysis:

The core principle of hardfacing is to melt the hardfacing material (welding wire, welding rod, or metal powder) through a heat source (such as electric arc, plasma, laser, etc.) and form a metallurgical bond or partial mechanical adhesion with the metal substrate surface to form a reinforced layer with specific functions.

This reinforced layer is usually harder and more wear-resistant than the original base material and can withstand high stress, high temperature, or corrosive environments.

The process flow of hardfacing:

-      Surface preparation: Remove oil, rust, and oxide scale from the surface of the workpiece.

-      Preheating treatment: Some high-carbon steel or alloy steel workpieces need to be preheated to prevent welding cracks.

-      Select the hardfacing method: Common methods include manual arc hardfacing, submerged arc welding, plasma hardfacing (PTA), laser hardfacing, etc.

-      Hardfacing operation: Depending on the wear area of the part, divide the hardfacing into sections and control the weld width and hardfacing layer thickness.

-      Post-heat treatment and cleaning: Reduce stress concentration, grind and shape to ensure dimensional and structural integrity.

Which equipment is suitable for build-up hardfacing repair?

Build-up hardfacing is not only suitable for surface pre-strengthening treatment of new equipment, but also widely used in the repair of worn parts of old equipment. The equipment suitable for build-up hardfacing repair mainly includes the following types:

•  Mining and construction machinery

    Excavator bucket teeth, bucket edges, conveyor scraper blades

    Crusher hammer heads, grinding rollers, screen plates

•  Metallurgy and building materials equipment

    Rolling mills, ball mills, rolling rolls, welding molds

    Rotary kiln support wheels, bearing housings, cutting heads

•  Power and boiler equipment

    Burner nozzles, superheater tubes, fan blades

    Wear-resistant parts in power plant desulfurization equipment

•  Agricultural and food processing machinery

    Plowshares, rotary plow blades, crushing tools, pressing screws

    Through hardfacing repair, the service life of these equipment can be extended by 2–10 times, effectively avoiding production downtime and high expenses caused by frequent replacement.

The Difference Between Hardfacing and Thermal Spraying

Although hardfacing and thermal spraying are both metal surface modification technologies, there are fundamental differences between them in terms of process principles, coating properties, and applicable scenarios.

Hardfacing involves melting metal materials using a heat source and forming a strong metallurgical bond with the substrate. The weld layer is usually thick, reaching several millimeters or even tens of millimeters. The reinforced layer is not only wear-resistant but can also withstand strong impact loads, making it more suitable for heavy-duty equipment operating under harsh conditions with severe part wear.

Thermal spraying involves heating metal or ceramic materials to a semi-molten state and then propelling them onto the workpiece surface via high-speed gas flow to form a thin mechanically bonded coating. The sprayed layer does not form a metallurgical bond with the substrate, and its wear resistance and bonding strength are usually lower than those of hardfacing, but it has less heat impact and deformation, making it more suitable for corrosion protection of precision parts and thin-walled parts.

Simply put, hardfacing is suitable for heavy-duty repair of parts with high wear and high impact, while thermal spraying is more suitable for applications that require precision and corrosion resistance but have relatively light loads.

Comparison of Different Surfacing Materials

Common surfacing materials include:

•  Iron-based alloys

•  Nickel-based alloys

•  Cobalt-based alloys

•  Tungsten carbide

Iron-based alloys are the most commonly used overlay welding materials, offering excellent versatility and low cost, and are suitable for most wear-resistant applications, such as bucket teeth, grinding discs, conveyors, and other components.

Cobalt-based alloys (such as the Stellite series) have excellent resistance to high-temperature erosion and intermetallic wear, and are often used for hardfacing critical surfaces of valves, molds, and cutting tools. However, they are relatively expensive and are suitable for precision and high value-added components.

Nickel-based alloys have excellent corrosion and oxidation resistance and are often used in chemical equipment, boiler tubes, the petroleum industry, and other corrosion-resistant environments.

Tungsten carbide-reinforced alloys, such as tungsten carbide or chromium carbide, are suitable for extreme wear conditions, such as high-speed impact equipment, cement vertical mills, and mining crushing components. They have extremely high hardness but also high brittleness.

When selecting materials, factors such as operating temperature, load type, corrosive medium, welding method, and maintenance budget should be comprehensively considered to avoid blindly selecting high-cost materials, which may lead to overdesign or unnecessary cost waste.

How to choose the appropriate hardfacing process?