OK8/BK8
GOST OK8/BK8 (ОК8/БК8) · GB YG8 · ISO K20
ОК8/ БК8 (VK8) is a GOST straight WC-8%Co cemented carbide, equivalent to YG8, with the extra cobalt raising toughness at the expense of hardness.
Reference datasheet — OK8/BK8 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the M condition
OK8/BK8 tempers and conditions
OK8/BK8 is supplied in 4 conditions, soft to hard. M is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
MDefault Thermomechanically controlled processed | Standard GOST/GB grade: best all-round balance of hardness and toughness for roughing tools, dies and wear parts. | — | 1,200 | 0 | 1,450 HV | 75 W/m·K |
ВК8-В | Choose for impact-dominated duty — rock drill inserts, percussive bits, heavy blanking dies — where toughness matters more than hardness. | — | 1,250 | 0 | 1,330 HV | 80 W/m·K |
ВК8-ВК | Maximum toughness and thermal-shock resistance for mining/geological drill teeth and heavily shocked wear parts; lowest hardness of the family. | — | 1,300 | 0 | 1,250 HV | 85 W/m·K |
Hot isostatic pressed | Pick when the highest transverse rupture strength and fatigue life are needed — precision punches, thin-web inserts, high-pressure sealing parts. | — | 1,400 | 0 | 1,500 HV | 78 W/m·K |
What is OK8/BK8?
ОК8/ БК8 (VK8) is a GOST straight WC-8%Co cemented carbide, equivalent to YG8, with the extra cobalt raising toughness at the expense of hardness. It is the CIS default for roughing and general wear parts and is supplied as inserts, rods, strips, tips and wear components in M, V, VK and HIP conditions. Elastic modulus is 600 GPa, thermal conductivity 75 W/m·K and maximum service temperature about 800 °C. Being a straight WC-Co grade it craters when cutting steel at speed, so use a P-group grade such as C7 there; drop to VK6 when finish and wear resistance matter more than impact strength. OK8/BK8 has a density of 14.6 g/cm³ (0.527 lb/in³), heavier than 92% of ceramic grades. It melts at 1,320°C (2,408 °F). OK8/BK8 has a tensile strength of 1,200 MPa (174 ksi), stronger than 94% of ceramic grades. Elongation at break is 0% and the elastic modulus is 600 GPa (87 Msi).
What is OK8/BK8 used for?
- roughing cast iron
- mining tools
- wear parts
Advantages
- Tough — resists crack growth — 14.5 MPa·√m (13.2 ksi·√in), better than 97% of ceramic grades
- Stiff — 600 GPa (87 Msi), better than 91% of ceramic grades
- Polishes to a fine finish — 92/100, better than 89% of ceramic grades
Limitations
- Heavy — 14.6 g/cm³ (0.527 lb/in³), worse than 92% of ceramic grades
- High embodied carbon — 30 kg CO₂/kg, worse than 91% of ceramic grades
- Needs corrosion protection — 45/100, worse than 90% of ceramic grades
OK8/BK8 properties
Typical room-temperature values for OK8/BK8-M; bars are the position among ceramic grades.
Physical3
OK8/BK8 has a density of 14.6 g/cm³ (0.527 lb/in³), heavier than 92% of ceramic grades. It melts at 1,320°C (2,408 °F).
Mechanical13
OK8/BK8 has a tensile strength of 1,200 MPa (174 ksi), stronger than 94% of ceramic grades. Elongation at break is 0% and the elastic modulus is 600 GPa (87 Msi).
Thermal5
OK8/BK8 is rated for continuous service to 800°C (1,472 °F). It conducts heat at 75 W/m·K (43.3 BTU/hr·ft·°F), better than 73% of ceramic grades. Thermal expansion is 5.2 µm/m·K (2.89 µin/in·°F).
Electrical2
OK8/BK8 has an electrical resistivity of 2×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is fair (45/100), worse than 90% of ceramic grades.
Sustainability4
Producing a kilogram of OK8/BK8 takes about 420 MJ of energy and emits 30 kg of CO₂ — more than 93% of ceramic grades. Typical recycled content is 30%.
Manufacturability3
OK8/BK8's machinability is not recommended (4/100, worse than 85% of ceramic grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the ceramic family
Yield strength against density for every ceramic grade FabDigit runs. OK8/BK8 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with OK8/BK8
Is OK8/BK8 easy to machine?
Sintered blanks are shaped only by diamond grinding, wire/sinker EDM or laser; green (presintered) blanks can be turned/milled with carbide tooling before final sintering.
Can OK8/BK8 be welded?
Not fusion weldable — join by vacuum/induction brazing with Ag-Cu-Zn or Cu-Mn filler onto steel bodies, using a ductile Cu interlayer to absorb CTE mismatch.
Can OK8/BK8 be formed, bent or molded?
Made by powder metallurgy: pressing/CIP or extrusion of WC-Co spray-dried powder, then vacuum or sinter-HIP consolidation at ~1400–1450 °C with ~18–22 % linear shrinkage.
OK8/BK8 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cobinder phase | 7.5 – 8.5 | 8 |
| C (free/total dev.)carbon balance controlled to avoid eta-phase or free graphite | ≤ 0.1 | — |
| Fe+Ni+other impuritiesresidual from milling media and raw powders | ≤ 0.5 | 0.2 |
| WCtungsten carbide hard phase, medium grain | ≥ 91.5 (balance) | — |
What surface finishes work on OK8/BK8?
Diamond lapping/polishing to Ra <0.05 µm; PVD TiN/TiAlN or CVD coatings applied for cutting tools; light sandblasting or Co-etching used as coating pretreatment.
Equivalent designations
Standards and trade names that resolve to OK8/BK8 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ISO
- K20
- GB (China)
- YG8
- GOST
- ОК8/БК8
How much does OK8/BK8 cost?
OK8/BK8 is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
OK8/BK8 — frequently asked
What is OK8/BK8 used for?
OK8/BK8 is typically used for roughing cast iron, mining tools and wear parts. In short: tougher CIS WC-Co grade; roughing and impact duty; standard mining tool carbide.
What is the tensile strength of OK8/BK8?
OK8/BK8 has a typical tensile strength of 1,200 MPa (174 ksi) — stronger than 94% of ceramic grades. Strength varies by condition: see the 4 listed tempers.
Is OK8/BK8 easy to machine?
Not especially — machinability is rated not recommended (4/100, worse than 85% of ceramic grades). Sintered blanks are shaped only by diamond grinding, wire/sinker EDM or laser; green (presintered) blanks can be turned/milled with carbide tooling before final sintering.
Can OK8/BK8 be welded?
Not fusion weldable — join by vacuum/induction brazing with Ag-Cu-Zn or Cu-Mn filler onto steel bodies, using a ductile Cu interlayer to absorb CTE mismatch.
What surface finishes work on OK8/BK8?
Diamond lapping/polishing to Ra <0.05 µm; PVD TiN/TiAlN or CVD coatings applied for cutting tools; light sandblasting or Co-etching used as coating pretreatment.
Can OK8/BK8 be formed, bent or molded?
Made by powder metallurgy: pressing/CIP or extrusion of WC-Co spray-dried powder, then vacuum or sinter-HIP consolidation at ~1400–1450 °C with ~18–22 % linear shrinkage.
What is the maximum service temperature of OK8/BK8?
OK8/BK8 is rated for continuous use to about 800°C (1,472 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does OK8/BK8 cost?
OK8/BK8 is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ГОСТ 3882-74 — Сплавы твёрдые спечённые. Марки — Госстандарт / Rosstandart (1974)
- ISO 513 — Classification and application of hard cutting materials — ISO (2012)
- ASM Handbook Vol. 2 — Properties of Cemented Carbides — ASM International (1990)
- ISO 4505 — Hardmetals, metallographic determination of porosity and uncombined carbon — ISO (1978)
- WC-8%Co medium/coarse grain hardmetal grade data — Zhuzhou Cemented Carbide / Sandvik Hard Materials (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.