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Cobalt base alloys typically contain tungsten and carbon for strengthening. Carbon has low solid solubility in cobalt and therefore most of its partitions are in WC, W2C, M6C or other carbides. These hard phases have a strengthening effect, giving such alloys high hardness and strength at temperatures under 800P.
The cobalt-chromium-tungsten-carbon alloys generally have excellent properties to resist high temperature, oxidation and thermal fatigue. Cobalt has a hexagonal-close-packed (hep) crystal structure at temperatures below 417C. Intrinsically, it has low coefficient of friction resulting in excellent wear resistance. At temperatures above 417C, cobalt transforms from HCP to FCC (face-centered-cubic) crystal structure, thereby, generating thermal stresses.
Therefore, it is recommended that in weld overlaying and spraying, the parts being coated are pre-heated to 500-600C to avoid cracking in the coating or overlay.
Specification
Cobalt base alloys typically contain tungsten and carbon for strengthening. Carbon has low solid solubility in cobalt and therefore most of its partitions are in WC, W2C, M6C or other carbides. These hard phases have a strengthening effect, giving such alloys high hardness and strength at temperatures under 800P.
The cobalt-chromium-tungsten-carbon alloys generally have excellent properties to resist high temperature, oxidation and thermal fatigue. Cobalt has a hexagonal-close-packed (hep) crystal structure at temperatures below 417C. Intrinsically, it has low coefficient of friction resulting in excellent wear resistance. At temperatures above 417C, cobalt transforms from HCP to FCC (face-centered-cubic) crystal structure, thereby, generating thermal stresses.
Therefore, it is recommended that in weld overlaying and spraying, the parts being coated are pre-heated to 500-600C to avoid cracking in the coating or overlay.
Specification
