Stellite

Source: Wikipedia, the free encyclopedia.

Stellite alloys are a range of cobalt-chromium alloys designed for wear resistance. "Stellite" is also a registered trademark of Kennametal Inc. and is used in association with cobalt-chromium alloys.

History

Stellite was invented by Elwood Haynes[1] in the early 1900s, initially as a material for making cutlery that would not stain or require constant cleaning. He was granted a patent for two specific alloys in 1907, and for two related ones in 1912; once he had these four patents he went into the business of producing his metal alloys. In the early 1920s, after considerable success during World War I in sales of cutting tools and high-speed machine tools made from Stellite, Haynes's company was bought by Union Carbide, becoming its "Stellite division", and continued to develop other alloys as well. The company was sold again in 1970 to Cabot Corporation, and in 1985 Cabot sold off the Stellite portion of the business.[2] The Stellite trademark was acquired by Kennametal in 2012.

Composition

Stellite alloys include a range of cobalt-based alloys, with significant proportions of chromium (up to 33%) and tungsten (up to 18%). Some of the alloys also contain nickel or molybdenum. Most of them have fairly high carbon content when compared to carbon steels.

Properties

Stellite alloys are a family of completely

wear resistance
, corrosion resistance, or ability to withstand extreme temperatures.

Stellite alloys display outstanding

cast so that only minimal machining is necessary. Due to the very high hardness many Stellite alloys are primarily machined by grinding, as cutting operations in some alloys cause significant tool wear even with carbide inserts. Stellite alloys also tend to have extremely high melting points
due to the cobalt and chromium content.

Applications

Typical applications for Stellite alloys include saw teeth, hardfacing, and acid-resistant machine parts. Stellite alloys were a major improvement in the production of poppet valves and valve seats for the valves, particularly exhaust valves, of internal combustion engines. By reducing their erosion from hot gases, the interval between maintenance and re-grinding of their seats was dramatically lengthened. Stellite alloys have also been used in some engines for the cam followers, particularly by the Norton Motorcycle Company.

The first third of the

bone replacements
out of precision-cast Stellite alloys. Stellite alloys are also used for making the cast structure of dental prostheses.

Stellite alloys have also been used in the manufacture of

lathes. With the introduction and improvements in tipped tools it is not used as often, but it was found to have superior cutting properties compared to the early carbon steel tools and even some high-speed steel tools, especially against difficult materials such as stainless steel
. Care was needed in grinding the blanks and these were marked at one end to show the correct orientation, without which the cutting edge could chip prematurely.

While Stellite alloys remain the material of choice for certain internal parts in industrial process valves (valve seat hardfacing), cobalt alloys have been discouraged in

half life that releases very energetic gamma rays. This phenomenon is more problematic in boiling water reactor (BWR) plants, since the steam is in direct contact with both the reactor and the steam turbine. Pressurized water reactor
(PWR) designs are less susceptible. While not a hazard to the general public, about a third to a half of nuclear worker exposures to radiation could be traced to reactor components made of cobalt alloys (or stainless steel with trace amounts of cobalt in it).

Stellite alloys have also used as the cage material for the first commercially available artificial heart valve, the Starr-Edwards caged-ball valve, first implanted in 1960.

Varieties

  • Talonite is an alloy similar to Stellite alloys which has been hot-rolled and hardened in a particular manner, to provide a combination of hardness, wear resistance and machinability. Not all Stellite alloys respond to this rolling process.
  • dentistry
    and medical implants.

Notes

  1. ^ "The WPI International Corporate Leaders Roundtable: The Impact of Evolving Technologies on the Future of Business: Notable Achievements of Alumni of Worcester Polytechnic Institute" Archived 2009-03-12 at the Wayback Machine. Elwood Haynes, Class of 1881.
  2. ^ "Haynes International - Our Company History". Archived from the original on 2023-02-01. Retrieved 2017-03-19.
  3. ^ "Stellite Lined Barrels". Archived from the original on 2021-09-23. Retrieved 2021-09-24.
  4. ^ "Torture Test: U.S. Ordnance MAG-58/M240 – Small Arms Defense Journal - Dan Shea - 28 February 2013". Archived from the original on 24 September 2021. Retrieved 24 September 2021.

External links

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