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StelliteFrom Wikipedia, the free encyclopedia
Stellite alloy is a range of cobalt-chromium alloys designed for
wear resistance. It may also containtungsten or molybdenum and a
small but important amount of carbon. It is a trademarked name of
theKennametal Stellite Company[1] and was invented by Elwood
Haynes[2] in the early 1900s as a substitutefor cutlery that
stained (or that had to be constantly cleaned).
Contents
1 Composition2 Properties3 Applications4 Varieties5 Notes6
External links
Composition
There are a large number of Stellite alloys composed of various
amounts of cobalt, nickel, iron, aluminium,boron, carbon, chromium,
manganese, molybdenum, phosphorus, sulfur, silicon, and titanium,
in variousproportions, most alloys containing four to six of these
elements.[3]
Properties
Stellite is a family of completely non-magnetic and
corrosion-resistant cobalt alloys of variouscompositions that have
been optimised for different uses. Information is available from
the manufacturer,Kennametal Stellite, outlining the composition of
a number of Stellite alloys and their intendedapplications. The
alloy currently most suited for cutting tools, for example, is
Stellite 100, because thisalloy is quite hard, maintains a good
cutting edge even at high temperature, and resists hardening
andannealing. Other alloys are formulated to maximize combinations
of wear resistance, corrosion resistance,or ability to withstand
extreme temperatures.
Stellite alloys display outstanding hardness and toughness, and
are also usually very resistant to corrosion.Stellite alloys are so
hard that they are very difficult to machine, and anything made
from them is, as aresult, very expensive. Typically, a Stellite
part is precisely cast so that only minimal machining isnecessary.
Stellite is more often machined by grinding, rather than by
cutting. The alloys also tend to haveextremely high melting points
due to the cobalt and chromium content.
Applications
http://en.wikipedia.org/wiki/Cobalt-chromehttp://en.wikipedia.org/wiki/Wearhttp://en.wikipedia.org/wiki/Tungstenhttp://en.wikipedia.org/wiki/Molybdenumhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Trademarkhttp://en.wikipedia.org/wiki/Namehttp://en.wikipedia.org/wiki/Elwood_Hayneshttp://en.wikipedia.org/wiki/Cutleryhttp://en.wikipedia.org/wiki/Cobalthttp://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Boronhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Chromiumhttp://en.wikipedia.org/wiki/Manganesehttp://en.wikipedia.org/wiki/Molybdenumhttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Magnetismhttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Cutting_tool_(machining)http://en.wikipedia.org/wiki/Hardening_(metallurgy)http://en.wikipedia.org/wiki/Annealing_(metallurgy)http://en.wikipedia.org/wiki/Wear_resistancehttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Toughnesshttp://en.wikipedia.org/wiki/Machininghttp://en.wikipedia.org/wiki/Casting_(metalworking)http://en.wikipedia.org/wiki/Grinding_machinehttp://en.wikipedia.org/wiki/Melting_point
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Typical applications include saw teeth, hardfacing, and
acid-resistant machine parts. Stellite was a majorimprovement in
the production of poppet valves and valve seats for the valves,
particularly exhaustvalves, of internal combustion engines. By
reducing their erosion from hot gases, the interval
betweenmaintenance and re-grinding of their seats was dramatically
lengthened. The first third of the M2HBmachine gun and M60 machine
gun barrels (starting from the chamber) are lined with Stellite.
The lockinglugs and shoulders of Voere Titan II rifles were also
made of Stellite. In the early 1980s, experiments weredone in the
United Kingdom to make artificial hip joints and other bone
replacements out of precision-castStellite alloys. It is also
widely used for making the cast structure of dental prostheses.
Stellite has also been used in the manufacture of turning tools
for lathes. With the introduction andimprovements in tipped tools
it is not used as often, but it was found to have superior cutting
propertiescompared to the early carbon steel tools and even some
high speed steel tools, especially against difficultmaterials such
as stainless steel. Care was needed in grinding the blanks and
these were marked at oneend to show the correct orientation,
without which the cutting edge could chip prematurely.
While Stellite remains the material of choice for certain
internal parts in industrial process valves (valveseat hardfacing),
its use has been discouraged in nuclear power plants. In piping
that can communicatewith the reactor, tiny amounts of Stellite
would be released into the process fluid and eventually enter
thereactor. There the cobalt would be activated by the neutron flux
in the reactor and become cobalt-60, aradioisotope with a five year
half life that releases very energetic gamma rays. While not a
hazard to thegeneral public, about a third to a half of nuclear
worker exposures could be traced to the use of Stelliteand to trace
amounts of cobalt in stainless steels. Replacements for Stellite
have been developed by theindustry, such as the Electric Power
Research Institute's "NOREM", that provide acceptable
performancewithout cobalt. Since the United States nuclear power
industry has begun to replace the Stellite valve seathardfacing in
the late 1970s and to tighten specifications of cobalt in stainless
steels, worker exposuresdue to cobalt-60 have dropped
significantly.
Stellite was also used as the cage material for the first
commercially available prosthetic heart valve, theStarr-Edwards
caged-ball valve, first implanted in 1960.
Varieties
Talonite is an alloy similar to Stellite which has been
hot-rolled and hardened in a particular manner, toprovide a
combination of hardness, wear resistance and machinability. Not all
Stellite alloys respond tothis process.
Notes
1. Formerly Deloro Stellite Group. Acquired by Kennametal, Inc.
on March 1, 2012.2. "The WPI International Corporate Leaders
Roundtable: The Impact of Evolving Technologies on the Future
of
Business: Notable Achievements of Alumni of Worcester
Polytechnic
Institute"(http://www.wpi.edu/News/Conf/Roundtable/Barcelona/alumni.html).
Elwood Haynes, Class of 1881.
3. Kennametal Stellite database
(http://www.stellite.com/alloydatabase/nominal.asp)
External links
http://en.wikipedia.org/wiki/Sawhttp://en.wikipedia.org/wiki/Toothhttp://en.wikipedia.org/wiki/Hardfacinghttp://en.wikipedia.org/wiki/Acidhttp://en.wikipedia.org/wiki/Poppet_valvehttp://en.wikipedia.org/wiki/Valve_seathttp://en.wikipedia.org/wiki/Internal_combustion_enginehttp://en.wikipedia.org/wiki/M2_Browninghttp://en.wikipedia.org/wiki/M60_machine_gunhttp://en.wikipedia.org/wiki/Machine_gunhttp://en.wikipedia.org/wiki/Barrel_(firearms)http://en.wikipedia.org/wiki/Chamber_(weaponry)http://en.wikipedia.org/wiki/Voerehttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/Hip_(anatomy)http://en.wikipedia.org/wiki/Replacement_jointhttp://en.wikipedia.org/wiki/Tool_bithttp://en.wikipedia.org/wiki/Lathe_(metal)http://en.wikipedia.org/wiki/Tipped_toolhttp://en.wikipedia.org/wiki/Carbon_steelhttp://en.wikipedia.org/wiki/High_speed_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/Neutron_fluxhttp://en.wikipedia.org/wiki/Cobalt-60http://en.wikipedia.org/wiki/Radionuclidehttp://en.wikipedia.org/wiki/Half_lifehttp://en.wikipedia.org/wiki/Gamma_rayhttp://en.wikipedia.org/wiki/Electric_Power_Research_Institutehttp://en.wikipedia.org/wiki/NOREMhttp://en.wikipedia.org/wiki/Machininghttp://www.wpi.edu/News/Conf/Roundtable/Barcelona/alumni.htmlhttp://www.stellite.com/alloydatabase/nominal.asp
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www.stellite.com (http://www.stellite.com) Kennametal Stellite
company siteMaterial Safety Data Sheet for
Stellite(http://www.armstrongblue.com/Publications/msds__stellite_tips.htm),
includes table ofcompositions of individual variantsMMC Superalloy
Corp. (Mitsubishi Materials
Group)(http://group.mmc.co.jp/superalloy/en/index.html)
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Categories: Cobalt alloys Chromium alloys
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