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Stellite 21

Stellite 21

Material Type

Metal

Material Name

Stellite 21

Alternative Names

UNS R30021

Process Compatibility

CNC Milling, CNC Turning

introduction

Stellite 21 in CNC Machining

Stellite 21, also known as UNS R30021 or Co-Cr-Mo alloy, contains 27.5% Cr, over 5.5% Mo, 0.25% C, and other elements.

Containing over 5.5% Mo, Stellite is a low-carbon cobalt-chromium alloy strengthened with molybdenum. It exhibits lower hardness at room temperature but increases in hardness after cooling. It boasts excellent high-temperature corrosion resistance, abrasion resistance, as well as superior toughness and comprehensive mechanical properties. It is ideal for hardfacing various hot stamping dies.

Stellite 21 finds widespread applications across industries including aerospace, chemical, energy, petroleum, and natural gas. It is favored for applications such as valves, seals, nozzles, valve stems, turbine blades, various fluid valves, and valve seats. Precision machining is often required to meet specific dimensional and surface requirements, involving high-precision cutting, grinding, and precision milling.

Properties

Properties Table of Stellite 21

Mechanical Properties
Ultimate Tensile Strength About 1100 MPa
Yield Strength About 950 MPa
Young's Modulus(Elasticity) About 240 GPa
Elongation at Break 1-2 %
Hardness (without heat treament) About 50 HRC
Density 8.53 g/cm³
Physical Properties
Corrosion Resistance Good
Magnetism Non-Magnetic
Weldability Moderate
Thermal Properties
Thermal Expansion Coefficient 11.3 μm/m°C
Thermal Conductivity 14.6 W/m·K
Electrical Properties
Electrical Resistivity  62 μΩ*cm

TECHNOLOGY OVERVIEW

Basic Knowledge of Stellite 21

What is Stellite 21?

Stellite 21 is a cobalt-based alloy, also known as CoCrMo alloy. It is a tungsten-chromium-cobalt alloy composed of cobalt (Co), chromium (Cr) and molybdenum (Mo). It has excellent wear, corrosion and high temperature resistance.

Stellite 21 is commonly used in industrial applications that require high temperature wear and corrosion resistance, such as aerospace, petrochemical, and energy. Its stable mechanical properties, ability to maintain its strength and stability in high temperature environments, make it an ideal choice for manufacturing wear-resistant parts and high-temperature working components.

Advantages of Stellite 21

Wear Resistance

High Temperature Resistance

Strong Corrosion Resistance

Good Mechanical Properties

High Strength and Toughness

Excellent Processability

Good Weldability

Applications of Stellite 21

Combustion Chamber Parts

Turbine Parts

Custom Valves

Auto Parts

Chemical Parts

Pipeline Parts

Coal Mill Parts

FAQ

Machining Stellite 21 Buying FAQs

Machining Stellite 21 can be challenging due to its high hardness and toughness. Processes such as milling, turning, grinding, and EDM (electrical discharge machining) are commonly used. Carbide tooling and coolant are often necessary to achieve good results.
Stellite 21 can be welded using processes like TIG (tungsten inert gas) welding and laser welding. However, welding Stellite alloys requires careful attention to pre-heating, post-heating, and welding parameters to prevent cracking and maintain the alloy's properties.
Both Stellite 6 and Stellite 21 are cobalt-based alloys, but Stellite 6 is harder and more wear-resistant, making it suitable for high-speed cutting tools and molds; while Stellite 21 is tougher and suitable for situations where it needs to withstand impact forces, such as the manufacture of valves and pump impellers.
Stellite 21 is not typically used in biomedical applications due to its cobalt content, which can lead to adverse biological reactions in the human body. For medical applications, cobalt-free alternatives such as titanium alloys or ceramics are preferred.

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