Hardfacing wear plate is the application of a hard, wear-resistant alloy overlay onto a steel surface that experiences abrasive, erosive, or impact wear. It’s different from structural welding because the goal isn’t to join two pieces. The goal is to deposit a specialized alloy that resists wear better than the base plate, extending the service life of buckets, liners, chutes, crusher plates, and other components that get ground away in service.
The base plate can be mild steel (A36), structural steel, or existing AR plate. When new AR plate gets hardfaced, you’re stacking two wear-resistance strategies: the quench-and-tempered base provides moderate hardness (400-500 BHN) throughout the plate thickness, while the hardfacing overlay provides extreme surface hardness (550-700+ BHN) at the wear face.
Hardfacing Alloy Types
Chromium Carbide (CrC)
The most widely used hardfacing alloy for abrasion resistance. Iron-based matrix with a high volume fraction of chromium carbide (Cr7C3) particles. These carbides are extremely hard (1600-1800 HV) and resist abrasion from sand, rock, ore, and other minerals.
| CrC Subtype | Chemistry (approx) | Hardness | Abrasion Resistance | Impact Tolerance |
|---|---|---|---|---|
| Standard CrC | 4-5% C, 25-30% Cr | 55-60 HRC | High | Moderate |
| High-Chrome CrC | 5-6% C, 30-38% Cr | 58-65 HRC | Very high | Low |
| CrC + Niobium | 4-5% C, 25-30% Cr, 5-7% Nb | 58-65 HRC | Highest (CrC category) | Low-moderate |
| CrC + Boron | 3-4% C, 20-25% Cr, 1-2% B | 55-62 HRC | High | Moderate |
CrC overlays develop check cracks during cooling. This is normal. The cracks relieve thermal contraction stress and don’t affect wear performance. Crack spacing typically runs 1/4 to 1 inch between cracks depending on the specific alloy and deposit thickness.
Tungsten Carbide (WC)
The hardest practical hardfacing deposit. Discrete tungsten carbide particles (2000-2400 HV) are embedded in a metallic matrix during deposition. The WC particles protrude above the matrix surface and resist abrasion by the hardest minerals.
Delivery methods:
- Tubular wire with WC fill: Flux-core wire with WC granules in the core. The wire melts and deposits the WC particles in a matrix.
- Oxy-fuel rod with WC granules: A rod coating that contains WC particles, deposited with an oxy-acetylene torch. Provides precise control for small areas.
- PTA (plasma transferred arc): The highest quality WC overlay, with precisely controlled carbide distribution. Used for premium hardfacing on drilling tools and critical wear parts.
| WC Type | Particle Hardness | Matrix Hardness | Overall Resistance | Cost |
|---|---|---|---|---|
| Macro WC (crushed) | 2000+ HV | 45-55 HRC | Extreme abrasion | Very high |
| Spherical WC (sintered) | 2200+ HV | 45-55 HRC | Extreme + some impact | Highest |
| WC/W2C eutectic | 2400+ HV | 50-60 HRC | Maximum hardness | Very high |
WC hardfacing costs 5-15 times more per pound than CrC. It’s justified in applications where the wear rate with CrC overlay would require frequent re-facing (mining, quarrying, oil and gas drilling tools).
Complex Carbide
Multi-element alloys combining chromium, niobium, vanadium, tungsten, and/or boron to produce a deposit with multiple carbide types. These alloys are engineered for specific wear conditions:
- High-stress abrasion: CrC + NbC for combined hardness and toughness
- Abrasion + moderate impact: CrC + borides for a balance of hardness and crack resistance
- Erosion (particle impact): Specialized alloys with fine, evenly distributed carbides
Martensitic Iron
A simpler, cheaper hardfacing category. The deposit is essentially a high-carbon steel that air-hardens to 45-60 HRC. Lower wear resistance than CrC but better impact tolerance. Used where the wear environment includes significant impact (hammer mills, crusher mantles) that would fracture brittle CrC or WC deposits.
Application Patterns
The deposition pattern affects how the wear surface performs. Different wear mechanisms call for different patterns.
Stringer Bead Pattern (Parallel Beads)
The standard pattern. Parallel beads covering the entire surface, overlapping by 30-40% to ensure complete coverage.
Best for: Sliding abrasion, chute liners, bucket floors, conveyor wear plates
Application: Run straight, parallel beads across the surface. Overlap each bead by about 1/3 its width. Two layers: first layer beads run in one direction, second layer can run the same direction or perpendicular (crosshatch).
Crosshatch Pattern
Two layers of stringer beads, second layer perpendicular to the first. Creates a surface with carbides oriented in two directions for improved resistance to multi-directional abrasion.
Best for: Surfaces exposed to abrasion from multiple directions, conveyor chute intersections, hopper bottoms
Dot Pattern
Individual dots (circular weld puddles) deposited in a grid pattern with spaces between them. The dots provide hard contact points while the spaces allow material (soil, aggregate) to flow between them.
Best for: Ground-engaging tools (plow shares, tillage blades), surfaces where material flow is important, applications where the base plate flexibility must be preserved
Spacing: Typically 1-2 dot diameters between dots. The pattern is staggered (like brick laying) so that material passing over the surface always contacts at least one dot.
Waffle Pattern
Continuous beads in a grid pattern (like tic-tac-toe), creating square pockets between the weld beads. Similar concept to dot pattern but with connected bead paths.
Best for: Bucket lips, drag line buckets, surfaces where material retention in the pockets provides an autogenous wear layer (retained aggregate protects the surface between the hard beads)
| Pattern | Coverage | Material Use | Best Application |
|---|---|---|---|
| Stringer (parallel) | 100% | Highest | Uniform sliding abrasion |
| Crosshatch | 100% | Highest | Multi-directional abrasion |
| Dot | 30-50% | Lowest | Ground-engaging, flow surfaces |
| Waffle | 40-60% | Moderate | Bucket lips, retained aggregate |
Welding Procedure for Hardfacing Wear Plate
Step 1: Surface Preparation
Remove all existing worn hardfacing, rust, scale, and contamination. Grind to clean, sound base metal. If the base plate has worn through to less than 50% of its original thickness, replacement is usually more cost-effective than hardfacing.
Step 2: Preheat
Preheat based on the base plate material:
- Mild steel (A36): 100-200F for plate under 1 inch, optional for thinner
- AR400: 200-300F (see AR plate welding guide)
- AR500: 300-400F
- Manganese steel (Hadfield): No preheat (max interpass 500F)
Do not preheat manganese steel. Manganese steel must stay below 500F total temperature or it loses its unique work-hardening properties. Weld fast, let it cool, weld again.
Step 3: Apply Buffer Layer (If Needed)
A buffer layer between the base plate and hardfacing is needed when:
- The base plate is high-carbon or alloy steel (4140, AR500)
- The hardfacing alloy is sensitive to dilution from the base
- You need a ductile cushion to prevent delamination
Buffer materials: E309L stainless, E312 stainless, or ER70S-6 mild steel (for mild steel base plates). One to two passes thick.
On mild steel base plates with CrC hardfacing, many shops skip the buffer and accept higher dilution in the first hardfacing layer. The second hardfacing layer achieves full chemistry regardless. On AR plate or alloy steel bases, a buffer is recommended.
Step 4: Apply Hardfacing
Process options:
| Process | Deposition Rate | Best For | Notes |
|---|---|---|---|
| Stick (SMAW) | Low (2-4 lbs/hr) | Field work, small areas | Most versatile, lowest equipment cost |
| Open-arc flux-core (FCAW-S) | High (8-15 lbs/hr) | Production, large areas | Highest deposition, most common production method |
| Submerged arc (SAW) | Very high (15-30 lbs/hr) | Flat position, large plates | Best quality, flat only, automated |
| Oxy-fuel | Very low (1-2 lbs/hr) | WC application, small areas | Best for WC granule rods |
| PTA (Plasma) | Moderate (4-8 lbs/hr) | Precision WC overlay | Highest quality WC distribution |
Open-arc flux-core (self-shielded) is the production standard for CrC hardfacing on wear plates. The wire feeds from a spool, and the flux core provides its own shielding. No external gas needed. Typical wire sizes: .045, 1/16, 5/64, and 3/32 inch. Run DCEP at the manufacturer’s recommended voltage and wire feed speed.
Settings for typical CrC flux-core hardfacing (.062 wire):
| Parameter | Value |
|---|---|
| Polarity | DCEP |
| Voltage | 24-28V |
| Wire Feed Speed | 120-200 IPM |
| Contact-tip-to-work distance | 1" to 1-1/2" |
| Travel speed | 8-14 IPM |
| Bead width | 3/4" to 1-1/4" |
| Overlap | 30-40% of bead width |
Step 5: Number of Layers
First layer: Diluted by the base plate (or buffer layer). Typical hardness is 5-10 HRC below the alloy’s rated maximum. This layer bonds the overlay to the substrate.
Second layer: Minimal dilution from the first layer. Achieves near-full design hardness. This is the working wear surface for most applications.
Third layer: Full design hardness with zero meaningful dilution. Rarely necessary unless the specification requires guaranteed surface chemistry (mining specifications, for example).
Check hardness with a portable hardness tester after cooling. First layer on CrC: typically 50-55 HRC. Second layer: 58-63 HRC. These are typical ranges; the specific alloy’s data sheet provides exact expectations.
Step 6: Post-Weld Cooling
Slow cool hardfaced wear plates under insulation (ceramic fiber blanket) when the base plate is AR400 or higher. Rapid cooling of the hardfaced assembly risks hydrogen cracking in the AR plate HAZ and delamination at the hardfacing/base interface.
For mild steel base plates, air cooling is generally acceptable. The mild steel base doesn’t have the hydrogen cracking susceptibility of AR plate.
Check Cracking Explained
CrC and WC hardfacing deposits develop transverse check cracks during cooling. This is a normal, expected characteristic of these alloys. The cracks form because:
- The hard deposit has a different coefficient of thermal expansion than the base plate
- The deposit contracts more than the base during cooling
- The contraction stress exceeds the deposit’s (very low) ductility
- The deposit relieves stress by cracking at regular intervals
Check crack characteristics:
- Perpendicular to the bead direction
- Uniformly spaced (typically 1/4 to 1 inch apart)
- Extend through the hardfacing layer thickness
- Do not extend into the base plate or buffer layer
- Have smooth, clean faces (not jagged or irregular)
When to be concerned about cracking:
- Cracks running parallel to the bead (longitudinal) indicate possible hot cracking or improper procedure
- Cracks extending into the base plate indicate insufficient buffer or base metal issues
- Irregular, branching cracks indicate thermal shock from rapid cooling
- Delamination at the hardfacing/base interface indicates poor bonding or excessive dilution
Check cracks don’t reduce wear performance. In some applications, they actually help by providing stress relief during thermal cycling in service. The mineral or material being handled doesn’t preferentially attack the cracks because the cracks are narrower than most abrasive particles.
Hardfacing vs Replacing Wear Plate
The decision to hardface versus replace depends on the economics:
Hardface when:
- The base plate is still at adequate thickness
- The wear pattern is localized (one area wears faster than the rest)
- Field application where plate replacement requires disassembly
- Adding wear resistance beyond what AR plate alone provides
- The cost of hardfacing is less than replacement plate plus installation labor
Replace when:
- The base plate has worn to less than 50% of original thickness
- The plate has fatigue cracks or structural damage
- The entire surface is uniformly worn
- Pre-fabricated hardfaced plate (like Hardox Wearparts or CDP plate) is available in the right size
- The replacement can be done during a scheduled shutdown
Pre-fabricated chromium carbide overlay plate (CCO plate, or CDP - chromium carbide deposit plate) is factory-produced with a CrC overlay already applied to a mild steel backer. It’s available in standard sizes and can be cut and welded into place. This is often more cost-effective than field-applied hardfacing for new installations.
Hardfacing wear plate is as much about alloy selection and application pattern as it is about welding technique. Match the hardfacing alloy to the specific wear mechanism, use the right pattern for the material flow, and control dilution with proper layering. For information on welding the base plate itself, see the AR400/AR500 welding guide.