Cobalt Chromium Tungsten Alloy

Cobalt-chromium-tungsten alloy (CoCrW) is one of the Stellite alloys, which is a cemented carbide that is resistant to various types of wear and corrosion, as well as high-temperature oxidation. The so-called cobalt-based alloys. The Stellite alloy was originally a cobalt-chromium binary alloy, and later developed into a cobalt-chromium-tungsten ternary composition. Cobalt-chromium-tungsten alloy is mainly composed of cobalt, containing a considerable amount of chromium, tungsten and a small amount of nickel, molybdenum, silicon, carbon, niobium, tantalum and other alloying elements, and occasionally also contains 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.

The basic composition of cobalt-chromium-tungsten alloy is: Co: 50%~58%, Cr: 28%~30%, W: 4%~6%, Ni: 2%~4% and other alloy compositions, the melting point is 1470 ℃ .

It can be seen from the alloy composition that the cobalt content and tungsten content of the alloy are very high, so that the material has excellent high temperature performance and poor thermal conductivity. It is these characteristics that make cobalt-chromium-tungsten alloy sparks dark red during grinding, and the number of sparks is very small. It spreads rapidly, causing inefficiency and burns on the surface of the workpiece.

Cobalt-chromium-tungsten alloys are widely used in locomotive diesel engines, nuclear power plant valves, marine diesel engines and various aircraft.

Early cobalt-chromium-tungsten alloys were produced by non-vacuum smelting and casting processes. The alloys developed later, such as Mar-M509 alloy, are produced by vacuum smelting and vacuum casting because they contain more active elements such as zirconium and boron.

Generally, cobalt-chromium-tungsten alloy lacks a coherent strengthening phase. Although the medium-temperature strength is low (only 50-75% of nickel-based alloys), it has high strength, good thermal fatigue resistance and thermal corrosion resistance when it is higher than 980 °C. and anti-corrosion performance, and has good weldability. It is suitable for making guide vanes and nozzle guide vanes of aviation jet engines, industrial gas turbines, naval gas turbines, and diesel engine nozzles.