Influence of Carbon Content on Shock Hardening Behavior of Cobalt-Base Hardfacing Deposits

Abstract

In this investigation, an attempt has been made to study the influence of carbon content on shock hardening behavior of cobalt-base hardfacing deposits for hot forging dies. The welding consumables with different carbon additions have been developed to fabricate the deposited metals by shielded metal arc welding (SMAW) process. Results show that the shock hardening effect and shock toughness of cobalt-base hardfacing deposit both are decreased whereas the hardness of the hardfacing layers is increased with the increase of the carbon content. All deposited metals contain Co-rich matrix dendritic structure with a network of Cr-rich carbides. After room temperature (RT) shocking, the density of the network of carbides increases to some degree and metallic compound NiW precipitates from the matrix. After 600°C shocking, NiW disappears from the matrix. For as-deposited, stacking faults and dislocation are found to exist in the matrix sporadically. After RT shocking, the formation of dislocation walls and dislocation cells are present as a result of hair-like dislocation locking effect, and the twin is observed. These conduce to the hardness and strength of cobalt-base hardfacing deposits.

Keywords:

• Carbon content
• Cobalt-base hardfacing deposits
• Hardness
• Hot forging dies
• Shock hardening effect

ACKNOWLEDGMENTS

This work was supported by Funding of Jiangsu Innovation Program for Graduate Education, the Fundamental Research Funds for the Central Universities (CXLX12_0150).