Cobalt Alloy, commonly known as stellite
alloy, is an alloy composed of alloy elements such as Cr, W, C, etc., with a
carbon content of 0.7% to 3.0% and a chromium content of 25%. 33%, tungsten
content 3% to 25%, cobalt content 30% to 70%.
The role of cobalt is to make the alloy have high corrosion resistance and
obtain a solid solution matrix with good toughness. A large amount of chromium
makes the alloy have high oxidation resistance, and tungsten can increase the
high temperature strength of the alloy to improve the high temperature creep
resistance. The higher carbon content can form high hardness chromium carbide
and tungsten carbide, which makes the stellite alloy have good wear
resistance.
The metallurgical structure of the stellite alloy depends on the carbon
content and the content of other alloying elements. When the carbon content is
low, the microstructure contains a large amount of primary austenite dendrites,
the austenite dendrites are solid solutions of chromium and tungsten in cobalt,
and the matrix structure is a co-crystal of solid solution and chromium-tungsten
composite carbide. As the carbon content increases, the amount of austenite
decreases and the number of eutectics increases, manifesting as a hypoeutectic
structure.
When the carbon content is high, the microstructure has hypereutectic
characteristics, and the nascent coarse chromium-tungsten composite carbide is
distributed on the solid solution and the carbide eutectic substrate. By
adjusting the carbon content and the tungsten content in the alloy, a weld
overlay alloy having different hardness and toughness can be obtained. The
overall performance of stellite alloy is superior to other types of surfacing
metals.
Stellite Alloy has high thermosetting
properties and can maintain hardness of 350-500 HV at 500-700 °C, anti-abrasive
wear, corrosion resistance, impact resistance, thermal fatigue resistance, high
temperature oxidation resistance (1000 ° C) and resistance Excellent friction
and wear resistance between metals.