Hartmetallsorten

The Two Levers Behind Every Grade: Grain Size and Binder

Every grade in the table above is defined by two numbers. Grain size trades hardness against toughness: fine and ultra-fine grains (0.2-1.0 µm) maximize hardness, compressive strength and edge sharpness, while coarse grains (2.5-5 µm) absorb impact through thicker binder layers. Binder content tunes the same balance: cobalt from 3-8% favors hardness and erosion resistance, 9-12% is the balanced middle ground, and 13-25% is specified when impact and breakage resistance matter more than wear.

A simple mental model: abrasive wear attacks the surface grain by grain, so small hard grains resist it best. Impact damage travels through micro-cracks, which large grains and more binder interrupt and absorb. Identifying which mechanism dominates your application is the first step of grade selection.

Match the Grade to the Wear Mechanism

• Abrasion (sand, ore, sliding particles): fine-to-medium grain, 8-12% Co, hardness first.
• Impact (crushing, milling picks, misfed stamping): coarser grain, 12-16% Co, toughness first.
• Erosion (waterjet, slurry, blast nozzles): fine grain with low binder, or nano/binderless grades when corrosion accompanies erosion.
• Metal-to-metal sliding (drawing, rolling, forming): fine-medium grain, polished surface, 10-12% Co.

Typical Applications and Recommended Grade Families

Typical values based on common industry practice; our engineers tailor the final grade to your working conditions.

A Five-Step Selection Framework

1. Rank the failure mode — abrasion, impact, erosion or metal pickup? A worn surface tells you: polished = abrasion, chipped = impact, flow grooves = erosion.
2. Score hardness vs. toughness demand (1-5 each) — high hardness wins: fine grain, low binder; high toughness wins: coarse grain, more cobalt; both high: sub-micron with 10-12% Co.
3. Add temperature — above ~500 °C consider TaC/NbC additions or fine grain with controlled binder to resist thermal softening.
4. Add corrosion — acidic or saline media attack cobalt binder first; nickel binder or binderless grades are the answer.
5. Validate with datasheets — compare density, hardness, TRS and porosity class, and confirm the sintering route (HIP-processed material shows measurably fewer defects).

For a deeper walkthrough with worked examples, read our guide How to Choose Tungsten Carbide Grades for Wear Parts.

Three Mistakes That Shorten Carbide Life

• Specifying hardness alone — a 94 HRA grade can fracture on day three in a rock crusher. Always read hardness together with TRS.
• Over-adding cobalt as a safety margin — excess binder often doubles wear rate while solving a fracture problem that better process control could have prevented.
• Ignoring the sintering route — the same nominal grade can differ by 2 HRA and 500 MPa TRS between vacuum and HIP sintering.

Beyond Standard WC-Co

For corrosive slurry nozzles and mirror-finish components, our bindemittelfreies Wolframcarbid grades reach 93-94 HRA with no binder phase to corrode. For combined wear and impact duty, sub-micron grades deliver 93+ HRA with TRS above 3000 MPa — properties that were mutually exclusive a decade ago. For chemical and downhole environments, nickel-binder grades replace cobalt where corrosion resistance is mandatory.