Formation of bridges between diamond particles during sintering in molten cobalt matrix

• Published in: Journal of materials science Vol. 27; no. 17; pp. 4695 - 4697
• Main Authors: JONG-KU PARK, AKAISHI, M, YAMAOKA, S, FUKUNAGA, O, EUN, K. Y, YOON, D. N
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.09.1992
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Miscellaneous; Technical ceramics; Liquid metal; Zirconium; Sintering; Diamond; Experimental study; Cobalt; Foil; Composite material; Powder
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF01166008

Compacts of diamond powder mixed with iron-group metal powders (usually Co powder at volume fractions below 5%) are sintered at about 6 GPa and 1550 C to be used as cutting tools or rock drilling bits. Large (about 700 micron) diamond particles mixed with 70% fine cobalt powder were sintered at 5.25 GPa and 1500 C after wrapping in zirconium foil. During the sintering treatment faceted inter-particles bridges form, and their pale yellow colour in contrast to the dark yellow colour of the original diamond particles indicates that the bridge is a new phase reduced in nitrogen content due to the gettering effect of the zirconium foil. The morphological characteristics of the bridge and the adjacent particle indicate that the bridge is formed by migration of the inter-particle grain boundary and solution-reprecipitation through the liquid cobalt matrix. It is possible that these processes are induced by the coherency strain energy produced by nitrogen diffusion from the region ahead of the retreating boundaries, as has been observed in metal systems. 18 refs.