Bimetallic Wear Plate vs. NM400: What’s the Difference and Which One to Choose?

In industries where abrasion is a constant threat—mining, cement, steel, bulk handling—choosing the right wear plate is critical. Among the most commonly considered options are NM400 and bimetallic chromium carbide overlay wear plates (often referred to as CCO plates). While both are labeled “wear-resistant,” they are fundamentally different in terms of their manufacturing process, behavior in service, and optimal performance applications.

How They’re Made: Alloy Steel vs. Weld Overlay Technology

NM400 is a monolithic alloy steel plate—the wear-resistant properties are built into the entire plate during smelting and heat treatment. The hardness (~400 HB) results from a tempered martensitic structure formed through quenching and tempering.

By contrast, bimetallic wear plates are made by hardfacing a high-chromium alloy layer onto a mild steel base using open-arc or submerged-arc welding. This creates a dual-layer structure where the top overlay layer contains a dense concentration of Cr7C3 carbides, offering surface hardness up to HRC 58-65.

The difference in structure starts at the manufacturing level, resulting in vastly different field performance.

Structural Comparison: One-Piece Steel vs. Functional Layering

 Why CCO Plates Last Longer

● Layer Design for Longevity

With customizable configurations like 3+3mm, 4+6mm, or even 6+8mm (base + overlay), CCO plates sacrifice only the surface, while the base plate provides structural support after the wear layer is consumed. NM400 wears uniformly—once the surface is worn, the entire plate must be replaced.

● Repair & Maintenance Flexibility

NM400 plates are easier to process using standard welding and bending techniques. Some bimetallic wear plates and wear parts, such as rollers, crusher teeth, and scrapers, can be repaired by resurfacing the wear layer, extending the service life of critical areas without requiring complete replacement.

When to Use Each: Matching Material to Application

Choose NM400 when:

High impact resistance is needed

The wear environment is not extreme

Easy fabrication and shaping are important

Choose Bimetallic CCO Plate when:

Facing high levels of sliding abrasion (e.g., chute liners, hoppers, cyclones)

Extended service life is a cost priority

Final Thoughts: Performance Beyond Hardness

Hardness alone doesn’t determine wear life. Manufacturing methods, microstructure, and layering strategy matter more in many cases. That’s why chromium carbide overlay wear plates—though seemingly more expensive up front—can deliver much better lifecycle value under the right conditions.

When choosing between NM400 and bimetallic wear-resistant plate, consider:

Your abrasion level

Impact environment

Downtime costs

Fabrication capabilities

A small change in material choice can mean a significant difference in performance and total cost of ownership.