ERCOCR-E Filler Wire | ERCOCR-E Filler Wire CO21
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ERCoCr-E Filler Wire (Stellite® 21 / CO21 Cobalt-Chromium-Molybdenum Wire) Supplier in India
Nicorex Alloys is an ISO 9001 and ISO 14001 certified stockist and supplier of ERCoCr-E cobalt-chromium-molybdenum filler wire based in Mumbai, India. Commercially known as Stellite 21 welding wire or Co21 filler rod, this alloy is classified under AWS A5.21 and carries UNS R30021 (rod/castings), W73041 (wire), and W73021 (electrode) designations.
The “-E” suffix in ERCoCr-E indicates a completely different alloy system compared to Co-Cr-W grades. It is a Co-Cr-Mo alloy with no tungsten. Replacing tungsten with molybdenum gives Stellite 21 the highest corrosion resistance, cavitation resistance, and thermal shock resistance in the Stellite family. Its typical composition is approximately 27% chromium, 5.5% molybdenum, 0.20-0.35% carbon, and the balance cobalt (around 63%). As-welded deposit hardness is HRC 27-35, which is the lowest of the standard Stellite grades and makes it easier to machine. In service, however, Cobalt Alloy 21 work hardens significantly to about HRC 40-45 during metal-to-metal contact. This strain-induced hardening, combined with its good ductility (about 8-11% elongation), makes this CoCrMo hardfacing rod a top choice for sour-gas valve trim (NACE MR0175), hot forging dies, gas turbine overlays, and marine pump components.
Every shipment from Nicorex Alloys includes an MTC 3.1 as per EN 10204, a deposit hardness test report, a chemical analysis report, and PMI certification. Stellite 21 bare rods, continuous wire spools, and cast rods are available in all standard diameters for quick dispatch across India.
ERCoCr-E Cobalt 21 Filler Wire Technical Specifications
The full specification table for ERCoCr-E (Stellite 21 / Co21) filler wire, covering AWS classification, UNS designations, welding processes, rod/wire dimensions, and deposit properties, is given below.
| AWS Classification |
Bare Rod: ERCoCr-E per AWS A5.21 Continuous Wire: ERCCoCr-E per AWS A5.21 Coated Electrode: ECoCr-E per AWS A5.13 |
|---|---|
| ASME SFA Specification | SFA 5.21 (rod/wire), SFA 5.13 (electrode) |
| UNS Number | R30021 (rod/castings) | W73041 (wire) | W73021 (electrode) |
| AMS Specification | AMS 5385 (castings), AMS 5819 (rod/wire) |
| Welding Processes | GTAW (TIG), OAW (oxy-acetylene), PTA, GMAW (MIG) |
| Polarity (GTAW) | DCEN (DC Electrode Negative) |
| Shielding Gas | 100% Argon (GTAW, GMAW, PTA); N/A for OAW |
| TIG Rod Diameters | 1.6, 2.4, 3.2, 4.0, 4.8 mm (1/16″ to 3/16″) |
| TIG/OAW Rod Length | 1000 mm (36″) standard |
| OAW Cast Rod Diameters | 3.2, 4.0, 4.8, 6.4, 8.0 mm |
| MIG/PTA Wire Diameters | 0.9, 1.0, 1.2, 1.6 mm |
AWS Classification Explained: ERCoCr-E (Stellite 21 / Co21)
The ERCoCr-E designation follows the AWS A5.21 naming convention. Each code segment carries a specific meaning, broken down below.
| Designator | Meaning |
|---|---|
| ER | Electrode/Rod; suitable for GTAW and OAW filler applications |
| Co | Cobalt-base alloy |
| Cr | Chromium is the primary alloying element after cobalt |
| -E | Composition Group E; Co-Cr-Mo system (no tungsten) |
The “-E” suffix is the critical distinction. Groups -A, -B, and -C designate Co-Cr-W (tungsten-bearing) alloys such as Stellite 6, 12, and 1. Group -E replaces tungsten entirely with molybdenum, producing a fundamentally different carbide structure (M₂₃C₆ rather than M₇C₃/WC) and a deposit optimised for corrosion and cavitation rather than abrasion.
Chemical Composition of ERCoCr-E Weld Deposit (%)
The chemical composition of the ERCoCr-E weld deposit per AWS A5.21 is listed below in the table:
| Specification | Carbon (C) | Chromium (Cr) | Molybdenum (Mo) | Nickel (Ni) | Iron (Fe) | Tungsten (W) | Silicon (Si) | Manganese (Mn) | Cobalt (Co) |
|---|---|---|---|---|---|---|---|---|---|
| AWS Range (%) | 0.20–0.35 | 25.0–29.0 | 4.5–7.0 | 1.5–4.0 | 3.0 max | 0 max | 1.5 max | 1.0 max | Balance |
| Typical (%) | 0.25 | 27.0 | 5.5 | — | — | 0 | — | — | ~63 |
Low carbon at 0.20-0.35% keeps carbide volume fraction minimal. The CoCrMo solid-solution matrix (not carbides) drives corrosion resistance and cavitation performance, setting Cobalt 21 apart from every tungsten-bearing Stellite grade.
Deposit Hardness and Mechanical Properties of Stellite 21 (ERCoCr-E)
Key deposit and mechanical properties of Stellite 21 (ERCoCr-E), including elongation and impact resistance, are mentioned below in the table
| Specification | Deposit Hardness (2-layer GTAW) | Single-Layer Hardness | Work-Hardened Surface | Elongation (wrought) | Tensile Strength | Yield Strength |
|---|---|---|---|---|---|---|
| Typical Value | HRC 27–35 (280–350 HV) | HRC 22–30 (dilution-dependent) | HRC 40–45 (up to 550 HV) | 8–11% | 710 MPa (103 ksi) | 565 MPa (82 ksi) |
As-welded HRC 27-35 allows machining with standard carbide tools. In service, strain-induced FCC-to-HCP phase transformation pushes surface hardness to HRC 40-45; the deposit gets harder the longer it runs. That self-improving behaviour is Stellite 21’s defining mechanical trait.
Base Metal Compatibility for ERCoCr-E (Stellite 21) Hardfacing
ERCoCr-E (Stellite 21) hardfacing offers excellent weldability, low crack sensitivity, and broad compatibility with steel, stainless, nickel, and cobalt alloys.
| Parameter | Information |
|---|---|
| Compatible Base Metals | Carbon steels, low-alloy steels, austenitic stainless steels, tool steels, nickel-base alloys, cobalt-base alloys |
| Preheat – Carbon & Low-Alloy Steels | 200–300 °C, about half the preheat typically required for Stellite 1 |
| Preheat – Austenitic Stainless Steels | No preheat required |
| Crack Sensitivity | Lowest crack sensitivity among the Stellite family |
| Welding Characteristics | High ductility allows wider weaving and higher heat input |
| Weldability vs Other Stellite Grades | Easier to weld than Co6 and Co12, with reduced risk of check cracking |
Recommended Welding Parameters for ERCoCr-E Co21 Hardfacing
GTAW (TIG) parameters for ERCoCr-E on DCEN polarity with 100% argon shielding are listed below. Higher currents than Co1/Co12 are acceptable due to Co21’s low crack sensitivity.
| Rod Diameter | Current Range (A) | Notes |
|---|---|---|
| 1.6 mm | 60–90 | Fine overlays, thin substrates |
| 2.4 mm | 80–120 | General-purpose hardfacing |
| 3.2 mm | 100–150 | Standard valve and die work |
| 4.0 mm | 130–170 | Heavy build-up, large components |
OAW uses a neutral flame setting. PTA operates at 100-200 A. Preheat carbon steel to 200–300°C and keep the interpass temperature below 450°C. Slow cooling is recommended but less critical than with tungsten-bearing Stellite grades. Stress relief at 595-650°C if required by code.
Key Properties of ERCoCr-E (Stellite 21) Overlay
Five properties set ERCoCr-E apart from every other Stellite hardfacing alloy:
- Best cavitation erosion resistance in the Stellite family; the CoCrMo matrix absorbs impact energy without brittle fracture.
- Best corrosion resistance among all Stellite grades. NACE MR0175/ISO 15156 compatible for sour service hardfacing.
- Work hardening: surface hardness increases from HRC 27 to HRC 40-45 during service through strain-induced phase transformation.
- Thermal shock resistance: the ductile matrix withstands repeated heating and quenching cycles; ideal for hot forging dies.
- Machinable with carbide tooling at HRC 27-35 as-welded. Use correct speeds/feeds; the deposit work hardens rapidly under light passes.
Co21 is not suited for severe abrasion; low carbide volume means limited hard-particle wear resistance. For abrasive service, use ERCoCr-A (Co6) or ERCoCr-C (Co1).
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Industrial Applications of ERCoCr-E Stellite 21 Welding Filler Wire
Corrosion resistance, cavitation performance, and thermal shock tolerance drive the use of ERCoCr-E in four primary sectors where the CoCrMo system outperforms tungsten-bearing Stellite grades.
- Oil & Gas Sour Service: Co21 is used for sour-gas valve trim (seats, chokes, wellhead parts) in H₂S environments.
- Hot Forging and Stamping Dies: Stellite 21 protects hot forging and stamping dies and piercing plugs by combining thermal shock resistance with progressive work hardening at contact surfaces.
- Gas Turbine and Power Generation: Co21 TIG overlays on blades and combustors provide hot corrosion resistance and stable hardness up to ~815°C (1500°F).
- Marine and Chemical Processing: Marine pumps, chemical valve trim, and seawater-exposed parts.
Storage and Handling of ERCoCr-E
ERCoCr-E is a bare (uncoated) wire that requires no rebaking before use. Store rods and spools in a clean, dry area at ambient temperature. Co21 rods are less brittle than Co6/Co12/Co1 filler rods, making them easier to handle. Keep the wire free from oil, grease, and moisture to avoid deposit porosity.
Available Forms and Packaging
Nicorex Alloys stocks ERCoCr-E filler wire forms, diameters and packaging as mentioned below in the table:
| Form | Diameter | Packaging |
|---|---|---|
| TIG / OAW Bare Cast Rods (1000 mm length) | 1.6–4.8 mm | Sealed tubes or moisture-barrier cartons |
| OAW Cast Rods | 3.2–8.0 mm | Sealed tubes or moisture-barrier cartons |
| Continuous Drawn Wire on D200 / D300 Spools | 0.9–1.6 mm | D200 / D300 spools |
| Powder for PTA / HVOF | Not applicable | Moisture-barrier packaging |
How to Order ERCoCr-E Filler Wire from Nicorex Alloys
To order ERCoCr-E cobalt-chromium-molybdenum filler wire, provide the following 10 details:
- AWS Classification — ERCoCr-E per AWS A5.21 / ASME SFA-5.21
- Product Form — Bare cast rod, continuous wire on spool, or ECoCr-E covered electrode (AWS A5.13)
- Diameter(s) Required — Cast rod 3.2, 4.0, 4.8 mm; wire 0.9, 1.2, 1.6 mm
-
Quantity — In kg
- Welding Process — GTAW / OAW / GMAW / PTA / SMAW
- Target Deposit Hardness — HRC 27–35 as-welded (two-layer undiluted overlay)
- Base Metal Grade and Service Environment — Specify requirement (include NACE MR0175 if applicable)
- Testing Requirements — Deposit hardness, chemical analysis, PMI
- Certification — MTC 3.1 per EN 10204 (standard from Nicorex Alloys)
- Packaging Preference — Specify requirement and delivery address/timeline
Frequently Asked Questions
What is the price of ERCoCr-E (Stellite 21 / Co21) Filler Wire per Kg in India?
ERCoCr-E is usually the lowest-cost Stellite wire because it contains no tungsten, but the price depends on size, form, quantity, and cobalt market rates. Contact Nicorex Alloys for a current quote.
Why does Stellite 21 have no Tungsten, unlike other Stellite Alloys?
Stellite 21 uses about 5.5% Mo instead of W to create a Co-Cr-Mo system originally developed for implants (ASTM F75), delivering superior corrosion resistance in reducing acids but lower hardness and abrasion resistance.
What is the crack sensitivity of ERCoCr-E compared to other Stellite Grades?
ERCoCr‑E has the lowest crack sensitivity among Stellite grades due to low carbon and minimal brittle carbides, needing only 200–300°C preheat and rarely check‑cracking.
Can ERCoCr-E deposits be machined?
Yes, ERCoCr-E at HRC 27-35 can be machined with standard carbide tools like ERCoCr-A (Stellite 6), but it work hardens quickly, so correct speeds/feeds and avoiding light passes are essential.
Is Stellite 21 (ERCoCr-E) related to the medical implant Alloy ASTM F75?
Yes, ASTM F75 is a cleaner, tightly controlled CoCrMo variant of the original Stellite 21 chemistry, but ERCoCr-E welding wire is intended only for industrial hardfacing, not medical implants.
When not to use ERCoCr-E (Stellite 21)?
Avoid ERCoCr-E for severe abrasion, applications needing very high initial hardness for galling resistance, or service above about 650°C, where creep strength is critical.