Omkar Metal Corporation

Introduction to Stellite Alloys Stellite alloys are a group of cobalt-chromium 'super-alloys' consisting of complex carbides in an alloy matrix predominantly designed for high wear resistance and superior chemical and corrosion performance in hostile environments. The combination of Cobalt and Chromium also results in an extremely high melting point making them perfect for a range of intriguing applications from extreme cutting tools to hot section alloy coatings in gas turbines. They may also contain molybdenum or tungsten and a small amount of carbon to offer even greater performance for specific applications. The Stellite range of alloys were first developed by Elwood Haynes in the early 1900s as an alternative for cutlery that was susceptible to staining. Stellite is a trademarked name of the Deloro Stellite Company, now part of the Kennametal group. Stellite alloys are non-magnetic and typically associated with high corrosion resistance and as with many alloys, they are adaptable and can be refined for a range of specific applications. Due to their incredibly hard material properties, Stellite alloys are inherently difficult and often expensive to machine therefore some very precise casting and grinding machining methods are often employed. The carbides present in the Co-Cr-W-based stellite alloys are of chromium-rich M7C3 type. The trademark owners of Stellite claim that Stellite 6 is the most widely used of their range of Stellite alloys, offering a proven industry standard for general-purpose wear resistance, and high mechanical and chemical perfromance in hostile environments. Typical Chemical Properties of Stellite Alloys There are several types and variations of stellite superalloys containing varying levels of: titanium, silicon, sulfur, phosphorus, molybdenum, manganese, chromium, carbon, boron, aluminium, iron, nickel and cobalt in different quantities. Most of the stellite alloys contain four to six of these elements. The Carbon content (and hence carbide volume) of a Stellite alloy is incredibly influential on the materials performance. Therefore, it is possible to group Stellite alloys as follows: High carbon - designed for high wear applications Low carbon - for high temperature uses Low carbon / higher Chromium to combat corrosion Chromium is also an extremely important component of Stellite alloys, not only does it offer its high corrosion resistant properties to the alloy but it is also the predominant carbide former and it provides strength (as a solute) in the alloying matrix.