OK8/BK8 VK (ВК8-ВК)
Grade
GOST OK8/BK8 (ОК8/БК8) · GB YG8 · ISO K20
Maximum toughness and thermal-shock resistance for mining/geological drill teeth and heavily shocked wear parts; lowest hardness of the family.
Values for the VK condition
Other OK8/BK8 tempers and conditions
OK8/BK8 is listed in 4 conditions; see the grade overview at OK8/BK8.
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 |
VKThis page 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 VK?
OK8/BK8 VK is OK8/BK8 in the VK grade — maximum toughness and thermal-shock resistance for mining/geological drill teeth and heavily shocked wear parts; lowest hardness of the family. OK8/BK8 VK has a tensile strength of 1,300 MPa (189 ksi), stronger than 97% of ceramic grades. Elongation at break is 0% and the elastic modulus is 580 GPa (84.1 Msi). OK8/BK8 VK 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). M is the default condition FabDigit quotes; VK is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 18 MPa·√m (16.4 ksi·√in), better than 100% of ceramic grades
- Stiff — 580 GPa (84.1 Msi), better than 89% of ceramic grades
- Polishes to a fine finish — 92/100, better than 89% of ceramic grades
- Conducts heat well — 85 W/m·K (49.1 BTU/hr·ft·°F), better than 79% of ceramic grades
Limitations
- Needs corrosion protection — 41/100, worse than 94% of ceramic grades
- 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
OK8/BK8 VK properties
Typical room-temperature values for OK8/BK8 VK; 13 are specific to this condition. Other listed values are OK8/BK8 reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical3
OK8/BK8 VK 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 VK has a tensile strength of 1,300 MPa (189 ksi), stronger than 97% of ceramic grades. Elongation at break is 0% and the elastic modulus is 580 GPa (84.1 Msi).
Thermal5
OK8/BK8 VK is rated for continuous service to 700°C (1,292 °F). It conducts heat at 85 W/m·K (49.1 BTU/hr·ft·°F), better than 79% of ceramic grades. Thermal expansion is 5.2 µm/m·K (2.89 µin/in·°F).
Electrical2
OK8/BK8 VK has an electrical resistivity of 1.8×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is fair (41/100), worse than 94% of ceramic grades.
Sustainability4
Producing a kilogram of OK8/BK8 VK 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 VK's machinability is not recommended (6/100, better than 61% of ceramic grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with OK8/BK8 VK
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.
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.
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) | — |
OK8/BK8 VK — frequently asked
What is OK8/BK8 VK used for?
OK8/BK8 VK 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 VK?
OK8/BK8 VK has a typical tensile strength of 1,300 MPa (189 ksi) — stronger than 97% of ceramic grades. Strength varies by condition: see the 4 listed tempers.
Is OK8/BK8 VK easy to machine?
Not especially — machinability is rated not recommended (6/100, better than 61% 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 VK 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 VK?
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 VK 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 VK?
OK8/BK8 VK is rated for continuous use to about 700°C (1,292 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.