Weld Hard Facing: What is it & How to do it Correctly?

In heavy industry, whether it’s mining, agriculture, or earthmoving—steel doesn’t just “break.” It dies a slow death by abrasion, impact, and erosion.

Hardfacing (or hardsurfacing) is the metallurgical answer to this problem. It is the process of depositing a tough, wear-resistant alloy onto the surface of a softer, cheaper base metal. Instead of building an entire excavator bucket out of expensive wear-plate, you build it out of structural steel and “armor” the critical contact points with hardfacing.

Done correctly, it can extend part life by 300% to 500%. Done incorrectly, it can cause catastrophic under-bead cracking and rapid spalling.

Hard Facing

Hard facing is a type of welding that involves depositing a wear-resistant layer on a less wear-resistant metal. The purpose of hard facing is to extend the life of the base metal by protecting it from wear, abrasion, or corrosion (e.g., mining equipment and construction machinery).

Hard facing can be done with various methods, including welding, thermal spraying, and cladding. The most common method of hard facing is welding. This is because welding offers many benefits over other methods, such as the ability to deposit a variety of materials, control over the thickness of the deposited layer, and low cost.

Thermal spray methods are also commonly used for hard facing, especially when depositing ceramic materials.

Cladding is another option for hardfacing using hardfacing welding rods, but it generally has a lower deposition rate than either welding or thermal spraying.

Identifying Your Wear Type

You cannot select a rod until you know what is killing your part. There is no “universal” hardfacing rod.

Wear Type	Description	The Solution (General)
Abrasion	Grinding, scratching, or rubbing (e.g., sand, coal, gravel).	Chromium Carbide (High hardness, low ductility).
Impact	Pounding or battering forces (e.g., rock crushers, pile drivers).	Austenitic Manganese (Work-hardens under impact).
Metal-to-Metal	Rolling or sliding friction (e.g., rollers, tracks, shafts).	Martensitic Steel (Hard but tough).

Pro Tip: If you use an Impact rod for Abrasion, it will wear away instantly. If you use an Abrasion rod for Impact, it will shatter like glass.

The “Build-Up” vs. “Hardfacing” Rule

One of the most expensive mistakes fabricators make is using hardfacing wire to restore dimension.

• Build-Up Rods (Buffer): These are akin to “low alloy” structural steel (similar to E7018 but slightly tougher). They are designed to restore the shape of a worn part. They have high compressive strength but low abrasion resistance.
• Hardfacing Rods (Overlay): These are high-alloy (Chromium, Tungsten, Cobalt). They are designed for the surface only.

The Golden Rule: Never apply more than 2 to 3 layers of hardfacing. If a part is worn down by 1 inch:

1. Weld 7/8″ with Build-Up wire.
2. Weld the final 1/8″ with Hardfacing wire.

If you weld 1 inch of solid hardfacing, the internal stress will rip the coating off the base metal (Spalling).

What is Hard Facing Welding?

Hardfacing, also known as hardsurfacing, is the application of a wear-resistant material to a base metal. It can provide resistance to abrasion, erosion, or impact.

Hardfacing can extend the service life of a component by depositing a layer of harder material on its surface. This process can be used to repair worn-out or damaged parts, or to strengthen components that are subject to high levels of wear.

During Hardfacing a special filler metal is applied to the base metal to be hard-faced, and then the two metals are fused together. The filler metal must have a higher hardness than the base metal in order to be effective.

There are many different types of hardfacing materials that can be used, including chromium carbide, tungsten carbide and niobium carbide.

Hard Facing Methods

Hardfacing is a process of depositing a wear-resistant layer on the surface of a metal. This process can be done using various methods, including

1. Welding,
2. Thermal Spraying, and
3. Cladding.

• Welding is the most common method of hard facing, and it can be used to deposit both ferrous and non-ferrous metals. A variety of welding processes can be used, including arc welding, gas tungsten arc welding (GTAW), MIG, Metal Cored, Laser and plasma arc welding (PAW).

• Thermal spraying is another popular method, and it can be used to deposit both metals and ceramics. In thermal spraying, molten material is sprayed onto the surface to be coated. The molten material forms a metallurgical bond with the substrate and cools to form a wear-resistant layer.

• Cladding is a less common method, but it has the advantage of being able to deposit very thick layers.

The best hard facing method for a particular application will depend on the specific needs of the industry or company. Factors such as cost, durability, and ease of use must all be considered before making a decision.

Hard-facing Welding Rod

Hard-facing welding rods can be made from a variety of materials, including carbon steel, chromium, and tungsten.

AWS A5.13 Specification covers hard-facing welding rods or Stick welding or SMAW. All surfacing electrodes for shielded metal arc welding are covered in this specification.

Following are the types of hard-facing welding rods:

• Iron Base Hard facing rods. E.g., EFe-1, EFeMn-A, EFeCr-A2, etc.
• Nickel and Cobalt Base Hard facing rods. E.g., ECoCr-A, ENiCr-C, ENiCrMo-5A, etc.
• Copper Base Hard facing rods. E.g., ECuAl-A2, ECuSi, ECuNiAl, etc.

Hard Facing MIG Wire

Surfacing or hard-facing MIG wire is a welding wire used to build up worn-out or damaged parts. It can also be used to protect new parts from wear and tear.

The AWS A5.21 specification covers MIG and TIG hard-facing wires.

Hard-facing MIG wires and TIG wires are available in two forms:

1. Solid Hard facing MIG & TIG Wires,
2. Cored (metal cored & flux cored) Hard facing MIG & TIG Wires.

The commonly used Hard Facing MIG wires are:

1. Iron Base Hard facing Electrodes/ Filler wires: ERFe-1, ERFe-2, ERFeCr-A, etc.
2. Cobalt and Nickel base Bare electrodes for hard facing: ERCoCr-A, ERCoCr-B, ERNICr-A, etc.
3. Cobalt and Nickel base Metal cored & Flux cored electrodes: ERCCoCr-A, ERCNiCr-A, ERCNiCrMo-5A, etc.
4. Solid and Cored Copper base hard facing electrodes: ERCuAl-A2, ERCuSi-A, ERCuSn-D, etc.
5. Tungsten carbides electrodes, WC1, W₂C, WC2, etc.

Techniques & Patterns: Geometry Matters

How you lay the bead is just as important as the rod you use.

A. The “Waffle” (Cross-Hatch) Pattern

• Best For: Earthmoving in soil/dirt.
• Why: You lay beads in a square grid. The dirt gets packed into the “pockets” of the grid. The abrasive soil then rubs against the packed soil (dirt-on-dirt wear) rather than the steel. This is essentially “free” hardfacing.

B. Stringer Beads (Parallel vs. Perpendicular)

• For Sand/Fine Slurry: Weld beads parallel to the flow. This allows material to slide over smoothly without turbulence.
• For Large Rocks: Weld beads perpendicular to the flow. The rocks bounce over the ridges, taking the impact on the high points and protecting the base metal valley.

C. The “Dot” Pattern

• Best For: Heat-sensitive parent metals (like Manganese steel).
• Why: Spacing out dots prevents heat build-up that would embrittle the base metal.

The Manganese Trap (Warning!)

High-Manganese steel (Hadfield steel), commonly found in rock crusher jaws, is a metallurgist’s nightmare if you treat it like mild steel.

• Mild Steel: Loves Preheat.
• Manganese Steel: HATES Preheat.

If you heat Manganese steel above $260^{\circ}\text{C}$ ($500^{\circ}\text{F}$), it becomes brittle. When hardfacing manganese crushers:

1. Keep it Cool: Use the “skip welding” technique.
2. Monitor Temp: If you can’t touch it with a gloved hand, stop welding.
3. No Oxy-Fuel Cutting: Never cut manganese steel with a torch; the heat input destroys the temper.

“Check Cracking”: When Cracks are Good

If you are running a high-chromium carbide rod (often called “Sugar Scoop” or “Chrome-White Iron”), you will see cracks running across the bead every 1-2 inches.

Do not panic. This is called “Relief Checking” or “Cross-Checking.”

Because the alloy is so hard (60+ HRC), it shrinks significantly when cooling. If it didn’t crack, the stress would transfer to the base metal and snap the part. These fine cracks release the stress and are essential for a healthy hardface deposit.

Practical Checklist for Success

1. Clean the Surface: Hardfacing does not like grease. Old, fatigued metal must be ground away to expose fresh steel.
2. Use a Buffer Layer: If applying very hard alloy onto very soft steel, run a “Buffer Pass” (often 309L Stainless or specific low-alloy cushion wire) to absorb the shock.
3. Control Dilution: Keep your amperage low. You want the alloy to sit on top of the metal, not mix with it. High dilution reduces the hardness of your overlay.

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