ERCoCr-D Cobalt-Based Hardfacing Bare Rod / Welding Wire (High-Carbon Co-Cr-W Alloy)

1. Description & Applications

ERCoCr-D (commonly known as Cobalt Alloy 3 / Stellite 3 equivalent) is an extreme-hard-grade, high-carbon cobalt-based hardfacing alloy. It contains the highest carbon and tungsten content among the standard cobalt-based alloy series, providing exceptional resistance to severe abrasion, extreme metal-to-metal wear, particle erosion, and corrosion at elevated temperatures up to 800°C (1472°F). Due to its high carbide volume, it offers superior wear resistance compared to ERCoCr-A, B, and C, though with reduced thermal shock resistance.

Key Applications:

• Extrusion screws, barrels, and mixing elements for abrasive plastics

• Saw blades and woodworking machinery components

• Slurry pump sleeves, valve trims, and chemical processing wear parts

• High-wear industrial knives, shear blades, and agricultural shredding tools

Classification: AWS A5.21 ERCoCr-D / UNS R30003

2. Nominal Chemical Composition (wt%)

3. Mechanical & Deposit Properties (As-Welded)

• Hardness (As-Welded): 48 – 58 HRC (single or multi-layer deposit, exceptionally high wear resistance)

• High-Temperature Hardness: Maintains outstanding hardness and wear stability up to 650°C (1200°F)

• Deposit Structure: Dense austenitic matrix packed with high-volume primary chromium-tungsten carbides

• Machinability: Extremely difficult to machine due to high hardness and high carbide content; finishing must be performed exclusively by grinding using CBN or specialized abrasive tooling.

4. Welding Guidelines & Best Practices

1. Surface Preparation: Thoroughly clean all oil, grease, rust, paint, scale, and foreign matter from the base metal.

2. Preheating:

   • Preheating is critical and mandatory due to the very high alloy and carbon content. Preheat to 400°C – 600°C (750°F – 1110°F) depending on base metal thickness and restraint to prevent cracking.

3. Interpass & Cooling:

   • Maintain a high interpass temperature throughout deposition.

   • Slow cooling in a furnace or under thick insulating blankets (e.g., dry lime or vermiculite) is strictly required to prevent thermal shock and stress fractures.