Stellite is a cemented carbide resistant to various types of wear and corrosion as well as high temperature oxidation. That is, the so-called cobalt-chromium-tungsten (molybdenum) alloy or cobalt-based alloy.
Stellite was invented by American Elwood Hayness in 1907. Stellite alloys are mainly composed of cobalt, containing a considerable amount of nickel, chromium, tungsten and a small amount of alloying elements such as molybdenum, niobium, tantalum, titanium, lanthanum, and occasionally iron. According to the different components in the alloy, they can be made into welding wire, powder used for hard surface surfacing, thermal spraying, spray welding and other processes, and can also be made into castings and forgings and powder metallurgy parts.
According to the classification of use, Stellite alloys can be divided into Stellite wear-resistant alloys, Stellite high-temperature alloys and aqueous corrosion-resistant alloys. Under normal working conditions, it is actually both wear and high temperature resistance or wear and corrosion resistance. Some working conditions may also require high temperature resistance, wear and corrosion resistance at the same time. Under these circumstances, the advantages of Stellite alloys can be reflected more.
Cobalt is the main component of Stellite alloy, and contains a certain amount of nickel, chromium, tungsten and a small amount of molybdenum, niobium, tantalum, titanium, lanthanum metal elements. When performing composition detection, conventional chemical analysis methods can be used, or spark direct reading spectrometer can be used for analysis, or a handheld XRF analyzer can be used to perform rapid and non-destructive composition detection of Stellite alloy materials in a few seconds. Read alloy grades and major element compositions without destroying the test sample. Compared with chemical analysis and direct reading spectrometer analysis, handheld XRF analysis does not require sample processing, which is more efficient and convenient.
In the late 1930s, due to the need for turbochargers for piston aero-engines, cobalt-based superalloys were developed. In 1942, the United States first succeeded in making turbocharger blades with dental metal material Vitallium (Co-27Cr-5Mo-0.5Ti). In the process of use, this alloy continuously precipitates carbide phase and becomes brittle. Therefore, the carbon content of the alloy was reduced to 0.3%, and 2.6% of nickel was added to improve the solubility of carbide-forming elements in the matrix, which developed into HA-21 alloy. In the late 1940s, X-40 and HA-21 made casting turbine blades and guide vanes for aviation jet engines and turbochargers, and their operating temperatures could reach 850-870 °C. S-816, which appeared in 1953 for forging turbine blades, is an alloy that is solid solution strengthened with a variety of refractory elements. From the late 1950s to the late 1960s, four cast Stellite alloys were widely used in the United States: WI-52, X-45, Mar-M509 and FSX-414. Deformed Stellite alloys are mostly sheets, such as L-605, which are used to make combustion chambers and conduits. HA-188, which appeared in 1966, has improved antioxidant properties due to its lanthanum content. The Stellite alloy ∏K4 used in the Soviet Union to make guide vanes is equivalent to HA-21. The development of Stellite alloys should consider the resource situation of cobalt. Cobalt is an important strategic resource, and most countries in the world lack cobalt, which limits the development of Stellite alloys.
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