Editorial Feature

Stellite Alloys - Chemical Composition, Mechanical Properties and Common Applications

Topics Covered

Introduction
Chemical Properties
Mechanical Properties
Manufacturing Process
Applications
References

Introduction to Stellite Alloys

Stellite alloys are a group of cobalt-chromium 'super-alloys' consisting of complex carbides in an alloy matrix predominantly designed for high wear resistance and superior chemical and corrosion performance in hostile environments. The combination of Cobalt and Chromium also results in an extremely high melting point making them perfect for a range of intriguing applications from extreme cutting tools to hot section alloy coatings in gas turbines. They may also contain molybdenum or tungsten and a small amount of carbon to offer even greater performance for specific applications.

The Stellite range of alloys were first developed by Elwood Haynes in the early 1900s as an alternative for cutlery that was susceptible to staining. Stellite is a trademarked name of the Deloro Stellite Company, now part of the Kennametal group.

Stellite alloys are non-magnetic and typically associated with high corrosion resistance and as with many alloys, they are adaptable and can be refined for a range of specific applications. Due to their incredibly hard material properties, Stellite alloys are inherently difficult and often expensive to machine therefore some very precise casting and grinding machining methods are often employed.

The carbides present in the Co-Cr-W-based stellite alloys are of chromium-rich M7C3 type. The trademark owners of Stellite claim that Stellite 6 is the most widely used of their range of Stellite alloys, offering a proven industry standard for general-purpose wear resistance, and high mechanical and chemical perfromance in hostile environments.

Typical Chemical Properties of Stellite Alloys

There are several types and variations of stellite superalloys containing varying levels of: titanium, silicon, sulfur, phosphorus, molybdenum, manganese, chromium, carbon, boron, aluminium, iron, nickel and cobalt in different quantities. Most of the stellite alloys contain four to six of these elements. The Carbon content (and hence carbide volume) of a Stellite alloy is incredibly influential on the materials performance. Therefore, it is possible to group Stellite alloys as follows:

  • High carbon - designed for high wear applications
  • Low carbon - for high temperature uses
  • Low carbon / higher Chromium to combat corrosion

Chromium is also an extremely important component of Stellite alloys, not only does it offer its high corrosion resistant properties to the alloy but it is also the predominant carbide former and it provides strength (as a solute) in the alloying matrix.

Typical Chemical composition of stellite 1:

Elements Content
Cobalt, Co 57%
Chromium, Cr 28 - 32%
Tungsten, W 11 - 13%
Carbon, C 2 - 3 %
Silicon, Si 1.20%
Iron, Fe 1%
Nickel, Ni 1%
Other 1.50%

Mechanical Properties of Stellite 1 Alloy

The mechanical properties of stellite 1 are displayed in the table below:

Properties Metric Imperial
Density 8.69 g/cm3 0.314 lb/in3
Hardness, Rockwell C 50-58 50-58
Tensile strength 1195 MPa 173 ksi
Yield strength 1050 MPa 152 ksi
Modulus of elasticity 230 GPa 33.4x106 psi
Elongation at break <1% <1%

Manufacturing Processes of Stellite Alloys

Stellite alloys are produced by a range of different processes or methods including wrought or hot forging, hardfaced deposit, powder metal and casting depending on teh final appication.  Stellite is more difficult to machine and grind than steel, and hence requires high performance processing equipment and specialized machining tools. Due to its incredible toughness Stellite is often machined by grinding rather than cutting.

Currently Stellite base material is rolled into bar, sheet and plate forms. During forming, the size and orientation of the matrix in the alloy is optimized, so that the material achieves higher strength than traditional cast material. The alloy is then cut into blanks of different sizes, which are then processed into finished parts.

Stellite Alloy Applications

Some of the major applications of stellite include the following:

  • Saw teeth, hardfacing, and acid-resistant machine parts
  • Poppet valves, valve seats and exhaust valves of internal combustion engine
  • M2HB machine gun and machine gun barrels
  • Medical applications including manufacturing of artificial hip joints, other bone replacements and cast structure of dental prosthesis
  • Turning tools for lathes

Reviewed by Nick Gilbert

References

 

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Gilbert, Nick. (2020, July 29). Stellite Alloys - Chemical Composition, Mechanical Properties and Common Applications. AZoM. Retrieved on August 15, 2020 from https://www.azom.com/article.aspx?ArticleID=9857.

  • MLA

    Gilbert, Nick. "Stellite Alloys - Chemical Composition, Mechanical Properties and Common Applications". AZoM. 15 August 2020. <https://www.azom.com/article.aspx?ArticleID=9857>.

  • Chicago

    Gilbert, Nick. "Stellite Alloys - Chemical Composition, Mechanical Properties and Common Applications". AZoM. https://www.azom.com/article.aspx?ArticleID=9857. (accessed August 15, 2020).

  • Harvard

    Gilbert, Nick. 2020. Stellite Alloys - Chemical Composition, Mechanical Properties and Common Applications. AZoM, viewed 15 August 2020, https://www.azom.com/article.aspx?ArticleID=9857.

Comments

  1. jayasimha reddy jayasimha reddy India says:

    Nice valuable matter......

  2. Challa Kishore Chowdhary Challa Kishore Chowdhary India says:

    Precise explanation.At the every point has been covered.

  3. Pramod Pendse Pramod Pendse India says:

    can stellites be used as die material for cold forging?

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoM.com.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Submit