ERCoCr-A Cobalt-Based Hardfacing Bare Rod / Welding Wire

1. Description & Applications

ERCoCr-A (commonly known as Cobalt Alloy 6 / Stellite 6 equivalent) is the most widely used versatile cobalt-based hardfacing alloy. It provides excellent resistance to complex wear mechanisms involving high temperatures (up to 800°C / 1472°F), severe oxidation, metal-to-metal galling, corrosion, and thermal shock.

Key Applications:

• High-pressure/high-temperature valve seats and plugs

• Steam turbine blades and fluid control valves

• Hot shearing blades, extrusion dies, and forging tools

• Engine exhaust valves and chemical process equipment

Classification: AWS A5.21 ERCoCr-A / UNS R30006

2. Nominal Chemical Composition (wt%)

3. Mechanical & Deposit Properties (As-Welded)

• Hardness (As-Welded): 38 – 44 HRC (single or multi-layer deposit)

• High-Temperature Hardness: Retains significant hardness up to 650°C (1200°F)

• Deposit Structure: Austenite matrix with rich primary chromium/tungsten carbides

• Machinability: Machinable with carbide tooling; grinding is recommended for precision surface finishes

4. Welding Guidelines & Best Practices

1. Surface Preparation: Ensure the base metal surface is thoroughly cleaned of oil, rust, moisture, grease, and oxides prior to welding.

2. Preheating:

   • Preheating the base metal to 250°C – 500°C (480°F – 930°F) is recommended depending on the base material chemistry, thickness, and component geometry to minimize thermal stress and prevent micro-cracking.

3. Interpass & Cooling:

   • Maintain appropriate interpass temperature during welding.

   • Slow cooling in dry insulation powder (e.g., vermiculite or lime) or a temperature-controlled furnace after welding is strongly advised.