Cobalt Base

Low Carbon - High Temperature: Cobalt base alloys can generally be divided into two categories. The low carbon alloys are formulated for high temperature applications where stress rupture properties are a major concern. Because of cost, these alloys are usually cast as inserts or smaller parts in a larger component and then other alloys are used for the main structural components. A good example of the use is as internal valve components for super heated steam applications. Exact alloy formulation follows corrosion resistant steels but takes into account the solubility of the alloying elements in a cobalt matrix. Castability is excellent and the cast parts are usually used in the as-cast condition with further heat treatment. Precaution must be taken to avoid contamination from non-cobalt base alloys during melting.

High Carbon - Wear Resistant: The second grouping of generally used cobalt based alloys is for wear resistant applications where high hardness must be maintained at elevated temperatures. Again because of cost, these alloys are usually cast as inserts or smaller parts in a larger component and then other alloys are used for the main structural components. Wear rings and applications for non-lubricated contacting parts are examples of use. Formulations of these high carbon cobalt alloys rely on a high carbon content to form various carbides in the matrix. Many similarities can be drawn from tool steel formulations but with different solubility's of the cobalt matrix. Tungsten, chromium and boron are the most common carbide forming elements while solid solution strengthening elements such as nickel, molybdenum, manganese and silicon are varied to optimize specific performance characteristics. Castability is excellent with high fluidity giving good edge definition. These alloys are normally used in the as-cast non-heat treated condition. As carbide content increases, the ductility of the cast alloy decreases to the point that Rc 50 parts can be broken with light taps of a hammer.