Regensburg 2010 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 26: Poster Session
MM 26.20: Poster
Dienstag, 23. März 2010, 14:45–16:30, Poster C
X-ray diffraction studies on diamond cobalt composites — •Andre Steffen1, Christian Kronholz2, Michael Paulus1, Christoph J. Sahle1, Manuel Ferreira2, Wolfgang Tillmann2, and Metin Tolan1 — 1TU Dortmund, Experimentelle Physik 1 / DELTA — 2TU Dortmund, Lehrstuhl für Werkstofftechnologie
Diamond grinding tools have widely established its usage in machining and cutting of natural stone and concrete. The interface area between diamonds and cobalt in diamond cobalt composites is of essential relevance for the grinding process and has been investigated by X-ray diffraction (XRD) studies. It could be shown that graphite is formed during the manufacturing process and that graphite is the main constituent of the diamond cobalt interface area. No strong (chemical) bonding in the form of cobalt carbide could be detected. By in situ and ex situ studies on ultra fine cobalt powders the thermal induced phase transformation between face centered cubic and hexagonal closed package phase of cobalt at T=421 °C has been investigated. At T=620 °C cobalt occures only in the fcc phase while both phases exist at room temperature (RT). The phase transformation, fcc to hcp during cooling from T>421 °C to RT, strongly depends on the cooling gradient. Furthermore it could be shown that the phase transformation, fcc to hcp, can be additionally induced by pressure. High pressure (P=550 MPa) leads to a high volume fraction of hcp phase (about 95 %).