Beijing Wenton technology

1. Stellite Alloy

Stellite is a category of cobalt-based wear-resistant, corrosion-resistant and high-temperature alloy, with cobalt as the matrix, chromium as the principal alloying element and carbides as the main strengthening phase. The typical systems are Co-Cr-W-C and Co-Cr-Mo-C. By dispersing high-hardness carbides (mainly M7C3 and M23C6 types) throughout the cobalt-chromium solid solution matrix, the material delivers high-temperature hardness (red hardness), wear resistance, cavitation resistance, corrosion resistance and oxidation resistance at the same time.

This class of alloy was first developed by the American inventor Elwood Haynes in the early 20th century. "Stellite" is now a registered trademark of Kennametal Inc. After more than a century of development, Stellite alloys have become the industry-wide material benchmark for severe service conditions such as valve sealing faces, hot shear blades, roller cone drill bit bearings and high-temperature wear-resistant liners.

1.1 Strengthening Mechanisms

The performance of Stellite alloys results from the synergy of three mechanisms:

Carbide dispersion strengthening: High-hardness chromium/tungsten complex carbides (hardness up to HV 1500 and above) are distributed throughout the matrix and directly resist abrasive cutting and ploughing. The higher the carbon content, the larger the carbide volume fraction and the stronger the wear resistance, with a corresponding decrease in toughness.

Solid solution strengthening and matrix toughness: Chromium delivers oxidation and corrosion resistance; tungsten and molybdenum raise high-temperature strength and red hardness. The cobalt matrix itself has low stacking fault energy and readily forms a dense, self-healing oxide film during sliding, significantly reducing adhesive wear and the tendency to galling.

Low friction and self-passivation: The oxide film formed on the sliding surface gives a low friction coefficient and a low susceptibility to metal transfer (galling), whether Stellite runs against Stellite or against stainless steel.

1.2 Key Performance Features

High-temperature hardness retention: Retains high hardness over the 600℃ to 800℃ range, which is beyond the reach of high-speed steel and most martensitic wear-resistant materials.

Combined abrasive wear and galling resistance: High-carbon grades resist abrasive wear; low-carbon grades resist galling and cavitation.

Cavitation and erosion resistance: Low-carbon grades (such as Stellite 21 and Stellite 6) perform outstandingly under high-velocity liquid flow conditions.

Corrosion and oxidation resistance: Chromium content is generally 25% to 33%, giving stability in oxidizing atmospheres and in a wide range of acid and alkali media.

Thermal shock and thermal fatigue resistance: The cobalt matrix has good thermal conductivity and a moderate coefficient of thermal expansion, so it resists spalling under alternating heating and cooling.

2. Classification of Alloy Systems

By chemical composition and strengthening mode, Stellite alloys are divided into four major systems:

In addition, the medical implant-grade CoCrMo alloy (ASTM F75, UNS R30075) is a sister branch of the Stellite alloy family, used for artificial joints, orthopedic implants and surgical instruments.

3. Grades and Chemical Composition

The table below gives the typical chemical composition (mass fraction, wt.%) and typical hardness of commonly used Stellite alloy grades. Cobalt is the balance (Bal.); all other elements are maximum values unless otherwise stated.

4. Mechanical and Physical Properties

4.1 Typical Mechanical Properties

High-carbon grades (Stellite 1, 3, 20 and 190) show extremely low elongation, typically only 1%–3%, which is characteristic of hardfacing materials. Designs should avoid subjecting them to impact loads.

4.2 Typical Physical Properties

5. Applicable Standards

The standard system for Stellite alloys follows three main lines: welding consumable standards, casting standards and aerospace material specifications. All Stellite products of Beijing Zhongye New Material Technology Co., Ltd. are manufactured in strict compliance with the following standards, subject to customer requirements.

5.1 International Standards

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