AISI T15 High-Speed Steel: Tungsten-Cobalt-Vanadium Super HSS
ASTM A600 · Published: 2026-06-01 · Updated: 2026-06-02
AISI T15 is the ultimate high-speed steel—a tungsten-cobalt-vanadium grade (1.50-1.60% C, 12.0% W, 4.0-5.0% Cr, 5.0% Co, 4.75-5.25% V) producing the highest wear resistance and hot hardness of any conventional HSS grade. The massive vanadium...
AISI T15 is the ultimate high-speed steel—a tungsten-cobalt-vanadium grade (1.50-1.60% C, 12.0% W, 4.0-5.0% Cr, 5.0% Co, 4.75-5.25% V) producing the highest wear resistance and hot hardness of any conventional HSS grade. The massive vanadium carbide population (5% V produces ~7-8 vol% MC carbides with 2800 HV hardness) provides abrasive wear resistance approaching cemented carbide while retaining the toughness and fabricability advantages of HSS. Hardens from 1,230-1,270°C (requires high-temperature salt bath or vacuum furnace—not achievable with conventional atmospheric furnaces). Triple temper at 540-560°C produces 65-67 HRC with secondary hardening. Used for broaches, form tools, and milling cutters for aerospace superalloys, titanium, and high-strength steels. The cobalt content sustains hot hardness at cutting temperatures above 600°C where M2 and M42 would soften. Grindability is poor due to MC vanadium carbides harder than conventional aluminum oxide wheels—requires CBN or diamond grinding.
Quick Facts
| Category | Tool Steel |
| Standard | ASTM A600 |
| Density | 8.20 g/cm³ |
| Yield Strength | 3,800 MPa (551 ksi) at 65-67 HRC |
| Tensile Strength | 4,100 MPa (595 ksi) at 65-67 HRC |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN HS12-1-5-5 | Compare |
| DIN 1.3202 | Compare |
| SKH57 | Compare |
| W12Cr4V5Co5 | Compare |
Related Materials
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Frequently Asked Questions
How does T15 compare to solid carbide for cutting tools?
Carbide (WC-Co) provides far superior wear resistance at higher cutting speeds but is brittle—unsuitable for interrupted cuts, form tools with complex profiles, or tools requiring sharp edge radii below 25 μm. T15 fills the space where carbide would chip (broaching, form turning, gear hobbing) but where M2/M42 wear too quickly. T15 costs 5-8× more than M2 but delivers 3-5× the tool life in nickel alloy and titanium machining.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu