Difference between overlay wear plate and normal wear plate
Difference Between Overlay Wear Plate and Normal Wear Plate: Structure, Hardness, Wear Mechanism, and Selection Guide
Overlay wear plate and normal wear plate are both used to fight industrial abrasion, but they are not the same material system. Overlay wear plate is a composite steel plate with a hardfaced wear-resistant layer on a weldable base plate. Normal NM wear plate is usually a quenched or quenched-and-tempered low-alloy steel plate with through-body hardness. The correct choice depends on wear mechanism, impact level, forming requirement, welding method, liner design, and lifecycle cost.
Choosing the Wrong Wear Plate Can Increase Liner Replacement, Welding Repair, Equipment Downtime, and Total Maintenance Cost.
Overlay plate is usually stronger in severe sliding abrasion. Normal NM wear plate is often better when forming, toughness, and impact resistance are more important.
Core Difference: Composite Wear Layer vs Through-Hardened Steel Plate
Overlay wear plate uses a base plate plus a hardfacing overlay layer. The wear-resistant layer contains high-hardness alloy carbides that do most of the abrasion resistance work. Normal wear plate, such as NM-type wear-resistant steel plate, relies on the hardness and toughness of the whole steel plate after rolling and heat treatment.
| Comparison Item | Overlay Wear Plate | Normal NM Wear Plate |
|---|---|---|
| Material Structure | Composite structure: steel base plate + hardfaced wear-resistant overlay layer. | Single steel plate structure, usually quenched or quenched-and-tempered low-alloy steel. |
| Wear Mechanism | Abrasion resistance mainly comes from high-hardness alloy carbides in the overlay layer. | Wear resistance mainly comes from the plate hardness and alloy steel matrix. |
| Typical Hardness Reference | Carbide hard phase can reach around HV1600 according to the original article. | Normal NM wear plate hardness is usually around HB350–500 according to the original article. |
| Best Use Case | Severe sliding abrasion, chutes, hoppers, liners, feeder plates, coal, cement, mining, and bulk material handling. | Impact-abrasion, structural wear parts, buckets, truck beds, cutting or forming parts, and general wear plates. |
| Weldability | Welding is usually done on the base plate side or prepared weld zones. | Generally weldable with proper procedure, preheating, and low-hydrogen practice depending on grade and thickness. |
| Forming | Can be formed within limits, but overlay cracks/checking and bending direction must be controlled. | Usually easier to bend and form than CCO overlay plate, depending on grade and thickness. |
What Is Overlay Wear Plate?
Overlay wear plate, also called wear-resisting composite steel plate, chromium carbide overlay plate, or CCO plate, is made by surfacing welding a hard alloy wear-resistant layer onto a common steel base plate. It combines the abrasion resistance of the overlay layer with the supporting strength, deformability, and weldability of the steel substrate.
Steel Base Plate
The base plate provides structural support, weldability, processing ability, and installation strength for the final liner or fabricated part.
High-Alloy Wear Layer
The overlay layer contains many hard alloy carbides. These carbides are the main anti-wear phase in severe abrasive service.
Visible Overlay Beads
Overlay wear plate often has visible surfacing welding passes or a weld bead pattern on the wear surface or plate edge.
What Is Normal NM Wear Plate?
NM wear-resistant steel plate is usually a low-alloy steel plate strengthened by rolling, quenching, or quenching-and-tempering heat treatment. Instead of having a separate hardfacing layer, the entire steel plate is designed to provide a balance of hardness, toughness, and structural performance.
Through-Plate Steel Grade
NM wear plate is a steel grade family, not a welded composite plate. The plate properties come from steel chemistry and heat treatment.
Typical HB Hardness Range
The original article describes normal NM wear plate hardness as usually HB350–500.
Better Toughness Balance
Compared with carbide-rich overlays, NM plate can offer better toughness and formability in many structural wear applications.
General Wear Fabrication
NM plate is commonly used for dump truck beds, buckets, cutting parts, crushers, screens, and structural wear components.
Overlay Wear Plate or Normal Wear Plate: Which One Should You Choose?
Do not choose by hardness alone. Start with the real failure mode: sliding abrasion, gouging, impact, temperature, corrosion, forming requirement, welding method, and liner replacement strategy.
| Working Condition | Better Direction | Reason |
|---|---|---|
| Severe sliding abrasion | Overlay wear plate | High-hardness alloy carbides resist abrasive cutting and scraping better in many liner applications. |
| High direct impact | Normal NM wear plate or tougher liner design | Toughness and crack resistance may be more important than carbide hardness. |
| Chute, hopper, feeder, transfer point | Overlay wear plate | Material sliding and continuous abrasion usually favor carbide-rich overlay surfaces. |
| Need bending, forming, or complex fabrication | Normal NM wear plate may be easier | Overlay plate can be formed, but bend radius, overlay direction, and cracking behavior must be controlled. |
| Replaceable liner package | Overlay wear plate or custom CCO liner | High-wear surface can be optimized while base plate supports welding, bolting, or stud installation. |
| Bucket and earthmoving structure | Case dependent | Side liners may use overlay plate, but structural shells and high-impact zones may need NM or other tough steels. |
Hardness Difference: Why HV Carbides and HB Plate Hardness Are Not the Same Thing
Overlay wear plate and normal wear plate use different hardness logic. Overlay plate may have extremely hard carbide phases inside the overlay layer, while normal NM plate uses bulk plate hardness such as HB350, HB400, HB450, or HB500 as a general material grade reference.
Overlay Wear Plate
The original page states that the wear-resistant layer contains many high-hardness alloy carbides, and the carbide hard phase can reach about HV1600.
This is a microstructural hardness value. It explains why carbide-rich overlay layers can resist severe abrasion.
Normal NM Wear Plate
The original page describes normal NM wear plate hardness as usually HB350–500.
This is bulk plate hardness. It reflects the overall strength and wear resistance of the quenched or tempered steel plate.
Buyer Warning
Do not directly compare HV carbide hardness with HB plate hardness as if they are the same test. They measure different things and represent different material behaviors.
Typical Applications
The best material depends on how the part fails. HALDEN can help review whether overlay wear plate, normal NM wear plate, AR steel, manganese steel, or a custom composite liner is more suitable.
Fabrication Difference: Cutting, Welding, Bending, and Installation
Material selection must consider not only wear life, but also how the plate will be cut, welded, bent, drilled, rolled, fixed, and replaced during maintenance.
Cutting
Normal NM wear plate can often be cut by thermal cutting methods with proper procedure. Overlay plate cutting may require process control because of the hard carbide layer.
Welding
Overlay wear plate is typically welded from the base plate side or at prepared weld zones. NM plate welding should follow the correct preheat and low-hydrogen procedure.
Bending and Forming
NM plate is usually easier to form. Overlay wear plate can be bent or rolled in certain conditions, but bend direction, radius, and overlay stress cracks must be considered.
Bolting and Studs
Both material types can be fabricated into replaceable liner systems. Overlay wear plate is often supplied with countersunk holes, plug weld holes, or stud-welded backing.
Field Replacement
For fast maintenance, HALDEN can design liner packages with bolt-on, plug-weld, or studded installation according to site needs.
Cost per Operating Hour
Compare not only plate price, but also cutting cost, installation labor, service life, downtime, replacement frequency, and repair accessibility.
Important Note: Overlay Plate Is Not Always Better, and NM Plate Is Not Always Cheaper in Real Service
Overlay wear plate may provide much longer life in severe sliding abrasion, but normal NM wear plate may be the safer choice for high-impact, highly formed, or structural applications. The right answer comes from wear mechanism analysis, not from a single hardness number or material name.
What Information Should You Send for Wear Plate Selection?
To recommend overlay wear plate, NM wear plate, or a custom composite liner, please send the real operating condition and current wear problem.
Application Information
- Equipment name and wear location
- Material handled
- Particle size, sharpness, and flow speed
- Impact level and abrasion severity
- Operating temperature and corrosion condition
Current Wear Problem
- Current plate material
- Current service life
- Photos of worn liners
- Failure mode: abrasion, impact, cracking, bending, peeling, or corrosion
- Target service life
Fabrication Requirement
- Plate size, thickness, and quantity
- Cutting, bending, rolling, or drilling requirement
- Welding, bolting, studding, or plug-weld installation
- Drawing or template
- Destination country and delivery term
Frequently Asked Questions
What is the difference between overlay wear plate and normal wear plate?
Overlay wear plate is a composite plate with a hardfacing wear layer on a steel base plate. Normal wear plate, such as NM wear plate, is a low-alloy steel plate strengthened by rolling and heat treatment.
Which plate is better for severe abrasion?
Overlay wear plate is usually better for severe sliding abrasion because its wear layer contains many high-hardness alloy carbides that resist abrasive cutting.
Which plate is better for high impact?
Normal NM wear plate or a tougher liner design may be better for heavy direct impact because toughness and crack resistance can be more important than carbide hardness.
Can overlay wear plate be welded?
Yes. Overlay wear plate is usually welded from the base plate side or through prepared weld zones. Welding directly on the hard overlay should be evaluated carefully.
What information is needed to choose the right wear plate?
Please provide the equipment name, wear location, material handled, particle size, impact level, current plate material, service life, photos, plate size, fabrication requirement, and installation method.
Not Sure Whether to Choose Overlay Wear Plate or Normal NM Wear Plate?
Send HALDEN your wear location, material handled, current liner photos, service life, impact level, and fabrication requirement. We can help review whether chromium carbide overlay plate, NM wear plate, AR steel, manganese steel, or a custom liner package is more suitable.
Please include these details:
- Equipment name, wear location, and photos of current worn parts
- Material handled, particle size, speed, impact level, and temperature
- Current plate material, thickness, service life, and target service life
- Required plate size, thickness, quantity, and drawing if available
- Cutting, bending, rolling, drilling, welding, bolting, or studding requirement
- Destination country, delivery term, and required inspection documents
