Hardfacing electrodes deposit wear-resistant alloy layers on base metal parts that see abrasion, impact, erosion, or metal-to-metal contact. They don’t join two pieces together; they build up or protect the surface of a single part. A bucket tooth, crusher jaw, tillage tool, or conveyor screw lasts 2-5 times longer with a properly applied hardfacing overlay. The right electrode selection depends on the type of wear, base metal, and service conditions.
Three categories cover most hardfacing work: buildup electrodes restore worn parts to dimension with machinable deposits, abrasion-resistant electrodes create hard surfaces that resist grinding and gouging wear, and impact-resistant electrodes handle repeated blows without cracking or spalling.
AWS Classifications
Hardfacing electrodes are classified under AWS A5.13 (surfacing electrodes for SMAW) and A5.21 (bare electrodes and rods for surfacing). The designations use a prefix-suffix system:
| Designation | Type | Hardness (Typical) | Primary Wear Resistance |
|---|---|---|---|
| EFe1 | Low-alloy buildup | 25-35 HRC | Moderate metal-to-metal |
| EFe2 | Medium-alloy buildup | 35-45 HRC | Metal-to-metal, moderate abrasion |
| EFe3 | High-alloy buildup | 45-56 HRC | Severe metal-to-metal |
| EFeCr-A | Chromium carbide | 55-62 HRC | Severe abrasion (low impact) |
| EFeCr-E | Complex carbide | 58-65 HRC | Extreme abrasion |
| EFeMn | Manganese steel | 18-22 HRC (work-hardens to 50+) | Severe impact |
| ECoCr-A | Cobalt-chromium (Stellite) | 38-48 HRC | Metal-to-metal, corrosion, heat |
| ENiCr | Nickel-chromium | 30-40 HRC | Corrosion + moderate wear |
| EWCr | Tungsten carbide | 55-65 HRC | Extreme abrasion and gouging |
The designation tells you the primary alloy system. “Fe” = iron base, “Cr” = chromium, “Mn” = manganese, “Co” = cobalt, “Ni” = nickel, “WC” = tungsten carbide. Each system targets different wear mechanisms.
Wear Types and Electrode Matching
Picking the right hardfacing electrode starts with identifying the wear type. Different wear mechanisms require different alloy properties.
Abrasion (Grinding, Gouging, Erosion)
Material scraping, grinding, or flowing across the surface. Examples: bucket teeth, plow blades, crusher liners, chute liners, auger flights.
Best electrodes: EFeCr-A (chromium carbide) for high-stress abrasion. EWCr (tungsten carbide) for extreme gouging where rocks and hard minerals dig into the surface. These deposits are very hard (55-65 HRC) and resist material removal, but they’re brittle under impact.
Key rule: High-abrasion deposits can’t take heavy impact. If the part sees both, you need to compromise or use a two-layer approach (impact-resistant buffer layer plus abrasion-resistant cap).
Impact (Hammering, Crushing, Battering)
Repeated blows that deform and break the surface. Examples: crusher hammers, rail switches, rock breaker points, coupling dogs.
Best electrodes: EFeMn (manganese steel, also called austenitic manganese). These deposits start soft (18-22 HRC) but work-harden under impact to 50+ HRC. The harder they get hit, the harder the surface becomes, while the subsurface stays tough and absorbs shock. Manganese steel hardfacing is the standard for impact applications.
Alternative: EFe2 and EFe3 buildup electrodes provide moderate impact resistance with more hardness than manganese steel. They work for medium-impact applications where pure manganese would be too soft between impacts.
Metal-to-Metal (Rolling, Sliding, Galling)
Two metal surfaces in contact under load. Examples: crane wheels, track rollers, shaft journals, spindles, gear teeth.
Best electrodes: EFe1, EFe2, or EFe3 buildup electrodes, depending on the hardness requirement. These are iron-based deposits with controlled alloy content that produce machinable (or near-machinable) surfaces. ECoCr-A (Stellite-type) for applications requiring corrosion and heat resistance in addition to wear resistance, like valve seats.
Corrosion + Wear
Combined chemical and mechanical attack. Examples: pump impellers, valve components, mixing blades in chemical processes.
Best electrodes: ECoCr-A (cobalt-chromium) for high-temperature corrosion with moderate wear. ENiCr (nickel-chromium) for lower temperatures with corrosion and moderate abrasion.
Application Method
Stringer Beads vs. Weave Beads
Stringer beads (straight, narrow passes) are preferred for most hardfacing. They cool faster, develop higher hardness, produce less dilution per pass, and create a more consistent deposit. Run parallel stringers side by side with slight overlap (about 25% of bead width) to cover the surface.
Weave beads (side-to-side oscillation) deposit metal faster but create higher heat input and more dilution. Use weave only for buildup electrodes where dilution isn’t critical or for buffer layers where hardness isn’t the priority.
Layer Sequence
Single layer: Adequate for light to moderate wear on parts that get replaced regularly. The first layer has the most dilution with the base metal, so it won’t reach full hardness.
Two layers: The standard for most hardfacing work. The first layer dilutes with the base metal. The second layer deposits on top of the first and reaches full alloy hardness. Two layers provide optimal wear performance.
Three or more layers: Rarely necessary except for extreme wear conditions or when using a buffer layer between a crack-sensitive hardfacing alloy and a carbon steel base.
Direction of Wear
Orient stringer beads perpendicular to the direction of wear (the direction material flows across the surface). This creates a washboard effect where each bead acts as a small dam, trapping the material between beads and reducing the contact area. Beads running parallel to the wear direction create channels that accelerate wear.
Preheat Requirements
Hardfacing electrodes deposit alloy compositions that are harder and more brittle than structural welding fillers. Without preheat, thermal shock and high cooling rates create cracking that extends into the base metal.
| Base Metal | Preheat Temperature | Notes |
|---|---|---|
| Low-carbon steel (A36, 1018) | 200 - 400F (93 - 200C) | Lower preheat for thin sections |
| Medium-carbon steel (1040, 1045) | 400 - 600F (200 - 315C) | Higher carbon needs more preheat |
| Manganese steel (Hadfield) | None (keep below 500F) | Manganese steel embrittles if overheated |
| Tool steel (H13, D2, O1) | 600 - 900F (315 - 480C) | Match to base metal tempering temp |
| Cast iron | 400 - 700F (200 - 370C) | Slow cool after overlay |
The manganese steel exception: Manganese steel (Hadfield, 11-14% Mn) must stay below 500F (260C) during welding. Above that temperature, carbides precipitate at grain boundaries and the steel becomes brittle. Weld short beads, let them cool, and move to another area. Keep checking temperature with a contact pyrometer.
Relief Cracks (Check Cracks)
High-hardness hardfacing deposits (above 50 HRC) typically develop a network of fine surface cracks during cooling. These are relief cracks, not defects. They form because the hard deposit contracts more than the ductile base metal underneath, and the deposit relieves the stress by cracking in a controlled pattern.
Relief cracks in chromium carbide and tungsten carbide deposits are:
- Normal and expected
- Surface-only (they don’t extend into the base metal)
- Not a failure indicator (they don’t affect wear performance)
- Beneficial in some cases (they break up large thermal stresses that could cause spalling)
If cracks extend into the base metal, the cause is usually insufficient preheat, wrong buffer layer, or applying a hard deposit directly to a crack-sensitive base metal without a transition layer.
Buffer Layers
A buffer layer is a softer, more ductile layer deposited between the base metal and the hard overlay. It serves three purposes:
- Absorbs thermal stress between the hard overlay and the more ductile base metal
- Prevents carbon migration from high-carbon hardfacing into the base metal HAZ
- Provides a compatible substrate for the hardfacing deposit, especially when the base metal alloy reacts poorly with the overlay chemistry
Common buffer layer electrodes: E309L stainless (for chromium carbide over carbon steel), EFe1 or EFe2 buildup rods (for general use), or the hardfacing manufacturer’s recommended buffer product.
Polarity and Settings
Most hardfacing electrodes run on DCEP. Some run on AC. Always check the manufacturer’s data sheet for the specific electrode you’re using. General guidelines:
Amperage: Run at the low to middle end of the recommended range. Lower amperage means less dilution, which preserves the alloy chemistry of the deposit. Too-high amperage dissolves too much base metal into the overlay, diluting the alloy and reducing hardness.
Travel speed: Moderate and consistent. Don’t linger, which increases dilution. Don’t rush, which creates thin, incomplete coverage.
Arc length: Short to medium. A long arc increases spatter and air exposure, which contaminates some alloy systems (particularly the cobalt and nickel-chromium types).
Common Applications Summary
| Application | Wear Type | Recommended Electrode | Layers |
|---|---|---|---|
| Bucket teeth, ripper tips | Abrasion + impact | EFeCr-A over EFe2 buffer | 2-3 |
| Crusher hammers | Severe impact | EFeMn | 2-3 |
| Plow blades, cultivator points | Abrasion | EFeCr-A | 1-2 |
| Conveyor screws, auger flights | Abrasion + erosion | EFeCr-A or EWCr | 2 |
| Crane wheels, track rollers | Metal-to-metal | EFe2 or EFe3 | 2-3 (build to dimension) |
| Shaft journals | Metal-to-metal | EFe1 (machinable) | 2-3 (build + machine) |
| Valve seats | Corrosion + metal-to-metal | ECoCr-A (Stellite) | 2 |
Cost Considerations
Hardfacing electrodes cost significantly more than structural electrodes. Chromium carbide rods run $15-30 per pound. Tungsten carbide rods cost $40-80 per pound. Stellite-type cobalt alloys can exceed $100 per pound.
The payoff is extended part life. A crusher hammer that lasts 400 hours without overlay might last 1,200 hours with proper hardfacing. At $500-2,000 per hammer replacement, the $30-50 in electrode cost pays for itself many times over. Add in reduced downtime for replacements, and the economic case for hardfacing is strong on any high-wear part.
Common Mistakes
No preheat on carbon steel: Applying a hard, brittle overlay to cold steel creates thermal shock that cracks into the base metal. Even low-carbon A36 benefits from 200-400F preheat before hardfacing.
Applying abrasion-resistant overlay where impact occurs: High-chromium carbide deposits (55-65 HRC) shatter under repeated impact. On crusher hammers and similar impact components, manganese steel (EFeMn) is the correct choice.
Running too hot: Excessive amperage increases dilution, mixing more base metal into the overlay. This reduces the alloy content and hardness of the deposit. Run at the low to middle range of the recommended amperage.
Skipping the buffer layer: Putting a hard, crack-sensitive overlay directly on medium-carbon or alloy steel often causes cracking into the base metal. A ductile buffer layer absorbs the thermal stress between the hard overlay and the more ductile base.
For the complete stick electrode lineup, see the stick electrodes selection guide. For standard structural electrodes, see the E7018 guide and E6011 guide.