What Is 1.2888 Steel
(X20CoCrWMo10-9)?

Overview & Definition

1.2888 steel — officially designated X20CoCrWMo10-9 under the DIN European standard — is a premium cobalt-alloyed hot work tool steel engineered for the most thermally demanding industrial tooling applications. With approximately 9.5–10.5% cobalt and 1.0–1.6% tungsten, it outperforms standard hot work grades like H13 wherever extreme heat, molten metal erosion, and thermal cycling converge.

Within the hot work tool steel family, 1.2888 occupies a unique high-performance tier. Its cobalt and tungsten content dramatically elevate hardness retention at elevated temperatures, resistance to molten metal attack, and service life in environments where standard grades fail prematurely. In the copper extrusion and magnesium die casting industries, it is the benchmark material — not an alternative.

The material is sometimes called RM10Co in some European trade contexts — a shorthand referencing its cobalt content. Despite no direct AISI/ASTM equivalent, it is widely specified across Europe, North America, and Asia for extrusion tooling, high-pressure die casting, and heavy-duty hot working components.

Decoding the DIN Designation

The name X20CoCrWMo10-9 is not arbitrary — it encodes the steel's chemical identity precisely. Understanding it tells you exactly what elements define this material:

The prefix X marks this as a high-alloy steel (total alloying elements exceed ~5%). The number 20 represents carbon content × 100, giving 0.20% C. The element symbols list the principal alloying elements in order of their defining influence. The suffix numbers 10-9 give the rounded nominal percentages of cobalt (~10%) and chromium (~9%).

Chemical Composition

The composition below conforms to DIN EN international standards. Jiangsu Liangyi enforces tight batch-to-batch elemental control — every supplied heat is fully documented in an EN 10204 3.1 Mill Test Certificate (MTC).

† Cobalt and Tungsten are the defining elements. Cobalt dissolves entirely in the iron matrix — raising the activation energy for dislocation movement at high temperature and preventing the early softening seen in cobalt-free grades. Tungsten forms thermally stable M₆C carbides that resist dissolution during austenitization, preserving hardness at service temperatures that would significantly soften H13.

Mechanical Properties After Heat Treatment

The values below represent typical properties for 1.2888 forgings in the quenched-and-tempered (Q+T) condition. Exact values vary with part geometry, heat treatment cycle, and testing direction — all documented in the EN 10204 3.1 MTC with each delivery.

Performance Profile at a Glance

Standard Heat Treatment Processes

Achieving the optimal balance of hardness, toughness, and thermal fatigue resistance in 1.2888 forgings requires precise heat treatment. Jiangsu Liangyi's experienced heat treatment team follows these standardized four-stage processes, with full customization available to client specifications:

• 1 — Soft Annealing 760 – 840 °C

  Furnace heat to 760–840 °C, followed by controlled slow cooling over 4–6 hours. Produces a maximum hardness of 320 HB. This softened condition is required before precision machining — cutting 1.2888 in its hardened state would destroy cutting tools and produce poor surface quality.

• 2 — Stress Relieving 600 – 650 °C

  Applied after rough machining to eliminate residual stresses introduced by forging and machining operations. Parts are held at 600–650 °C for 1–2 hours, then air-cooled in a controlled manner. This step minimizes dimensional distortion during the final hardening stage — critical for tight-tolerance tooling components.

• 3 — Austenitizing & Quenching 1,100 – 1,150 °C

  Parts are heated to 1,100–1,150 °C in a controlled-atmosphere or vacuum furnace. Hold time is calculated based on part cross-section thickness to ensure complete austenitization and carbide dissolution. Quenching is performed by air cooling, oil quenching, or vacuum quenching depending on part geometry and performance requirements. Post-quench hardness reaches approximately 52 HRC.

• 4 — Double / Triple Tempering 600 – 750 °C

  1.2888 requires multiple tempering cycles — typically 2–3 passes at precisely controlled temperatures — to fully transform retained austenite, eliminate internal quench stresses, and achieve the target hardness-toughness balance. Each cycle lasts a minimum of 2 hours. Final hardness is tuned by tempering temperature selection.

Premium Melting Methods

The quality of any forging begins with the ingot. For 1.2888, where cobalt and tungsten content must be precisely controlled and inclusion cleanliness is paramount, melting route selection is a critical engineering decision. Jiangsu Liangyi offers five certified melting routes:

• EAF

  Electric Arc Furnace — Standard baseline route. Meets commercial-grade specifications. Suitable for lower-criticality applications where cost is the primary driver.

• EAF+LF+VD

  EAF + Ladle Refining + Vacuum Degassing — Reduces hydrogen, nitrogen, and oxygen content. Typical route for standard industrial tooling applications requiring improved cleanliness.

• EAF+ESR

  EAF + Electro Slag Remelting — ESR dramatically reduces non-metallic inclusions and delivers a finer, more uniform microstructure. Strongly recommended for extrusion dies, die casting tooling, and all fatigue-critical components. Substantially improves fatigue life and batch-to-batch consistency.

• EAF+PESR

  EAF + Protective Atmosphere ESR — ESR conducted under protective atmosphere prevents re-oxidation during remelting. Produces lowest possible oxygen content and superior directional isotropy.

• VIM+PESR

  Vacuum Induction Melting + Protective Atmosphere ESR — The premium route. VIM eliminates dissolved gases completely; PESR delivers superior inclusion control. Specified for aerospace-grade precision tooling and highest-reliability critical applications.

All melting routes are fully traceable. Complete chemical analysis, heat numbers, and melting records are documented in the EN 10204 3.1 (or 3.2) Mill Test Certificate supplied with each delivery.

Industrial Applications of 1.2888 Steel

1.2888 is specified for the most demanding hot working environments across multiple industries. Its unique combination of cobalt-driven hot hardness and tungsten carbide stability makes it the material of choice wherever standard grades fail prematurely.

1.2888 vs H13 (1.2344): Head-to-Head

The choice between 1.2888 and H13 is one of the most consequential material decisions in hot work tooling. Both are excellent steels — but they serve different performance tiers. The table below is a technical comparison based on published material science data and industry experience — not customer reviews.

Key Metallurgical Advantages Explained

1 — Cobalt's Role in Hot Hardness

Cobalt dissolves completely into the iron matrix — it forms no carbides. Its effect is to raise the stacking fault energy of the matrix, which restricts dislocation cross-slip and climb mechanisms at elevated temperatures. In practical terms, the steel resists softening under sustained heat far longer than cobalt-free grades. At 600 °C, 1.2888 retains hardness values that H13 only achieves at approximately 400 °C.

2 — Tungsten's Role in Carbide Stability

Tungsten forms the highly stable M₆C carbide phase. Unlike the M₂₃C₆ carbides present in many standard hot work steels, M₆C resists dissolution during austenitizing and coarsening during tempering. These fine, dispersed carbides act as pinning obstacles to dislocation movement — directly contributing to exceptional wear resistance at service temperatures where other carbide types have already coarsened and lost effectiveness.

3 — Thermal Fatigue Mechanism

Thermal fatigue (heat checking) occurs when repeated temperature cycling creates tensile stresses on die surfaces during cooling. 1.2888's good thermal conductivity (aided by Cr content) and inherent resistance to surface oxidation minimize the temperature gradient across the die face — reducing the stress amplitude of each thermal cycle. The result: fewer heat check cracks, longer die life, and more consistent part quality over extended production runs.

4 — Molten Metal Erosion Resistance

When molten copper, magnesium, or zinc contacts a die surface, it attacks grain boundaries and dissolves iron into the melt — a process called soldering or erosive wear. The dense chromium oxide layer maintained by 1.2888's high Cr content acts as a diffusion barrier, while the cobalt-stabilized matrix resists dissolution at the metal-die interface far more effectively than H13 in these specific erosive environments.

Forging 1.2888 Steel: Process Essentials

Forging 1.2888 requires careful temperature control and experienced process management. Its cobalt and tungsten content mean the steel has a narrower hot working window than simpler grades — improper practice leads to surface cracking, internal segregation, or inadequate grain refinement. Key process parameters:

Jiangsu Liangyi's 26+ years of forging experience with high-alloy tool steels means these parameters are embedded in our standardized production processes. Our 80,000 m² facility operates a full production chain — from steel melting to final machining and inspection — under one ISO 9001:2015 certified quality system. 1.2888 open die forgings and seamless rolled rings

Frequently Asked Questions

Summary: What Makes 1.2888 Exceptional

1.2888 (X20CoCrWMo10-9) is a precision-engineered material for a specific tier of demanding applications that standard grades cannot adequately serve. Its defining strengths in one table:

When your tooling operates in conditions where heat, pressure, and molten metal converge — and where tool failure means production downtime and quality scrap — 1.2888 is the engineering answer. Its higher upfront cost is recaptured through extended service life, fewer replacements, and reduced unplanned downtime.

To source 1.2888 (X20CoCrWMo10-9) forged parts manufactured to your drawings and specifications, contact our technical team directly for a free quote within 24 hours.