YG6, YG8 and YG15 are tungsten carbide grades in the Chinese GB system, all part of the ISO K group (WC + cobalt). The number is the approximate cobalt percentage — YG6 = 6% Co, YG8 = 8% Co, YG15 = 15% Co. More cobalt means more toughness but less hardness and wear resistance. Picking the right grade is mainly a trade-off between abrasion resistance and impact resistance.
YG6, YG8, and YG15 are ISO K-class tungsten carbide grades where the number equals the approximate cobalt percentage. YG6 (6 % Co, ~89.5–91 HRA) is the hardest and most wear-resistant — for finishing tools, gauges, nozzles. YG8 (8 % Co, ~89–90 HRA) is the balanced general-purpose default — for rods and dies. YG15 (15 % Co, ~87–88 HRA) is the toughest — for impact-heavy work like cold-heading and stamping. More cobalt = tougher but less hard. For steel cutting, use ISO P (YT) grades instead.
The core trade-off: cobalt content
Tungsten carbide is hard WC grains bonded by a cobalt metal binder. The cobalt is what gives the material its toughness; the WC gives hardness and wear resistance. So as cobalt goes up:
- Hardness and wear resistance go down
- Toughness and impact resistance go up
That single relationship explains the whole YG6 → YG8 → YG15 ladder.
YG6 vs YG8 vs YG15 at a glance
| Grade | Cobalt | Hardness (HRA) | Character | Typical uses |
|---|---|---|---|---|
| YG6 | ~6% | ~89.5–91 | Hardest, most wear-resistant, lower toughness | Finishing cutting tools, wear parts, nozzles, gauges for cast iron & non-ferrous |
| YG8 | ~8% | ~89–90 | Balanced hardness & toughness | General-purpose tooling, dies, rods, parts with moderate impact |
| YG15 | ~15% | ~87–88 | Toughest, most impact-resistant, softer | Cold-heading & stamping dies, high-impact forming tools, mining tips |
(Exact values vary with WC grain size and the specific producer; treat these as typical ranges.)
Typical property values
| Property | YG6 | YG8 | YG15 |
|---|---|---|---|
| Cobalt content | ~6 % | ~8 % | ~15 % |
| Hardness | ~89.5–91 HRA | ~89–90 HRA | ~87–88 HRA |
| Bending strength (TRS) | ≥ ~1450 MPa | ≥ ~1500 MPa | ≥ ~2100 MPa |
| Density | ~14.6–15.0 g/cm³ | ~14.5–14.9 g/cm³ | ~13.9–14.2 g/cm³ |
| Wear resistance | Highest | Balanced | Lowest of the three |
| Impact toughness | Lowest of the three | Moderate | Highest |
(Typical values per the Chinese GB grade system; exact figures vary with WC grain size, producer and batch. Ask for the material certificate — cobalt %, hardness and TRS — with every production lot.)
When to choose each grade
Choose YG6 when abrasion dominates
If the part fails by wearing away — sliding wear, erosion, fine finishing — and impact is low, YG6's higher hardness gives the longest life. Good for nozzles, wear strips, gauges and finishing tools.
Choose YG8 for general-purpose work
When you need a sensible balance and aren't sure, YG8 is the safe default: hard enough to resist wear, tough enough to survive normal handling and moderate shock. Common for rods, dies and mixed-duty parts.
Choose YG15 when impact dominates
If the part takes repeated heavy blows — cold-heading dies, stamping/forming dies, percussive tooling — YG15's high cobalt content resists chipping and cracking, even though it is softer.
Rule of thumb
More abrasion → lower cobalt (YG6). More impact → higher cobalt (YG15). Unsure → start with YG8 and adjust after field testing.
When NOT to use each grade
- Don't use YG6 where impact or interrupted contact is significant — its low cobalt content makes it the most chip-prone of the three. A cold-heading die in YG6 will crack long before it wears.
- Don't use YG8 when one failure mode clearly dominates — if the part fails purely by abrasion, YG6 lasts longer; if it fails by chipping, YG15 survives longer. YG8 is a starting point, not a universal answer.
- Don't use YG15 for fine cutting edges or high-precision wear surfaces — it is the softest of the three and wears fastest. Its job is absorbing impact, not holding an edge.
Purchasing advice: specify the application, not just the grade
Grade names are not perfectly standardised between producers — one factory's “YG8” can differ noticeably from another's in grain size and real-world performance. In your RFQ, state the workpiece material, the operation, the impact level and the expected service life alongside the grade name, and ask for a material certificate (cobalt %, hardness, TRS) with each batch. If your current part chips, move one step up in cobalt; if it wears out without chipping, move one step down — our carbide die failure guide walks through reading each failure mode.
What about ISO P and M grades?
The YG (ISO K) family is for cast iron, non-ferrous metals and non-metallics. For machining steel, you generally need ISO P grades (YT / WC-TiC-Co), which resist the heat and cratering of steel chips. ISO M grades are multi-purpose, often used for stainless steel. A good supplier helps you map your material and operation to the right grade.
Key takeaways
- YG6/YG8/YG15 are ISO K carbide grades; the number ≈ cobalt %.
- Lower cobalt = harder & more wear-resistant; higher cobalt = tougher.
- YG6 for abrasion, YG15 for impact, YG8 as the balanced default.
- For cutting steel, look to ISO P (YT) grades instead.
Frequently Asked Questions
What's the difference between YG6, YG8, and YG15?
The number is the approximate cobalt percentage. YG6 = 6 % Co (hardest, most wear-resistant), YG8 = 8 % Co (balanced), YG15 = 15 % Co (toughest, most impact-resistant). More cobalt means more toughness but less hardness and wear resistance.
Which YG grade is best for cutting tools?
YG6 for high-precision finishing tools where wear is the main failure mode. YG8 for general-purpose cutting with moderate impact. YG15 is too soft for cutting tools — it's designed for impact-heavy applications like cold-heading and stamping dies.
Are YG grades suitable for machining steel?
No. YG (ISO K class) grades are designed for cast iron, non-ferrous metals, and non-metallics. For machining steel, you generally need ISO P grades (YT / WC-TiC-Co), which resist the heat and cratering caused by steel chips.
What's the hardness of YG6 vs YG8 vs YG15?
Typical Rockwell A hardness values: YG6 ~89.5–91 HRA, YG8 ~89–90 HRA, YG15 ~87–88 HRA. Exact values vary with WC grain size and the specific producer; treat these as typical ranges.
What is the bending strength (TRS) of YG6, YG8 and YG15?
Typical transverse rupture strength: YG6 ≥ ~1450 MPa, YG8 ≥ ~1500 MPa, YG15 ≥ ~2100 MPa. TRS rises with cobalt content — the same trade that lowers hardness raises fracture resistance. Values vary by producer and grain size; confirm with the batch material certificate.
Is there a big price difference between YG6, YG8 and YG15?
For finished custom parts, usually not — grinding, EDM and tolerance requirements drive far more of the cost than the grade itself. Choose the grade by failure mode, not price. Be cautious of quotes far below market: verify the material certificate rather than accepting a cheaper substitute grade.
Not sure which grade you need?
Send us your part, material and operation — we'll recommend the grade and supply the rods, dies or wear parts in YG6/YG8/YG15.
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