Exploring the Relationship Between Hardness and Toughness of Cemented Carbide Roll Rings

The hardness and toughness of cemented carbide roll rings are a pair of mutually constrained yet synergistically optimized key performance indicators. Their relationship directly affects the operational efficiency and safety of steel rolling production lines. Below is an analysis of their intrinsic correlation and strategies for balancing them in industrial applications from a materials science perspective:

I. Intrinsic Contradictions and Synergistic Mechanisms

Microstructural Antagonism

Hardness Source: Volume fraction (70-97%) and grain size (0.2-5μm) of tungsten carbide (WC) hard phase. Fine-grained structure (<1μm) enhances hardness (HRA 88-94) through grain boundary strengthening.

Toughness Source: Plastic deformation capability of cobalt (Co) binder phase (3-30%). A Co layer thickness ≥50nm effectively hinders crack propagation.

Performance Inversion Law

When Co content increases from 6% to 12%:

Hardness decreases by ~3-5 HRA.

Transverse rupture strength (TRS) improves by 20-30% (up to 2800 MPa).

Impact toughness (AK) increases by 40-60%.

II. Performance Balancing Driven by Rolling Conditions

III. Advanced Technologies for Performance Breakthroughs

Gradient Structure Design

Surface layer: Nanocrystalline WC (0.2μm) + 8% Co → HRA 93.

Transition layer: Co gradient increases (8%→12%) → Forms residual compressive stress field.

Core: Coarse-grained WC (2μm) + 12% Co → TRS 2500 MPa.

Effect: Surface wear rate reduced by 35%, thermal crack resistance improved by 50%.

Composite Strengthening Technology

Grain boundary modification: Add 0.5% Cr3C2 to inhibit WC grain growth, hardness increased by 1.5 HRA.

Binder phase optimization: Co-Ni-Re alloy enhances TRS by 15% while maintaining >95% hardness retention.

Stress regulation: Deep cryogenic treatment (-196°C × 4h post-sintering) reduces residual stress by 40%.

IV. Testing and Validation System

Performance Mapping Tests

Simultaneous HV30 hardness testing and TRS three-point bending experiments to establish HRA-TRS correlation curves.

Dynamic condition simulation: Thermomechanical coupling tests on MMS-2A testing machine (800°C + 500 MPa contact stress).

Hardness and toughness are two extreme rigid indicators. Higher hardness reduces toughness, increases steel throughput, but decreases roll ring service life and raises fracture risk. Lower hardness improves toughness, reduces throughput, extends service life, and significantly lowers fracture probability. Hunan Tianyi High-tech Materials Manufacturing Co., Ltd. is a professional carbide roller ring manufacturer with 24 years of experience. We can provide customized solution design and services for each customer's different application scenarios. Welcome to inquiry and communicate!