Wear of Transition Metal Rich Glassy Alloys
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WEAR OF TRANSITION METAL RICH GLASSY ALLOYS * SUNG H. WHANG AND B.C. GIESSEN Materials Science Division, Institute of Chemical Analysis, University, Boston, MA 02115, U.S.A.
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INTRODUCTION Transition metal rich glassy alloys constitute a large fraction of the known glassy metals. Their unique properties such as high mechanical strength, corrosion resistance and magnetic softness coupled with adequate thermal stability have stimulated many studies by academic as well as industrial researchers. By contrast, wear of glassy metals has been an almost completely neglected topic until now. Boswell reported non-linear behavior of abrasive wear on glassy Pd 7 8.1Cu5 5. Si 1 6. 4 (l). He also found varying wear behavior for different stages of the crystallization process. Recently, we have reported wear properties for Ti rich binary glasses which indicate that these glasses have high friction coefficients and high wear rates (2). In this paper, we review the results of a systematic investigation of the wear behavior of several types of glassy alloys rich in transition metals, focussing on the coefficient of friction, wear rate, surface morphology and wear mechanism. EXPERIMENTAL METHODS The geometries of most specimens available for wear testing are limited to ribbon shape for samples produced by a melt spinner and foil shape for samples produced by hammer and anvil quenching; both types of samples have a thickness of %20-40p. Accordingly, the available testing modes are restricted to the cylinder-on-plate, pin-on-plate, ball-on-plate or related geometries. For the present experiments, the cylinder-on-plate geometry was adopted. To prepare a sample, the ribbon or foil was cut into strips 4-5 cm long which were glued to a small aluminum piece which was then inserted into a holder. This holder was mounted on the wear tester and held against a cylindrical slider of 2.54 cm diameter. The slider materials were AISI 52100 steel or WC(80)-Co(20) plasma coated onto a wheel. The former slider, with a hardness of DPN'v600, was used for relatively soft alloys such as Ti and Zr rich glasses and the latter,
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*Communication No.
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118 from the Institute of Chemical Analysis,
University; Boston, MA 02115.
Schematic draw-
ing of sliding wheel wear tester used.
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302 having a hardness DPN%1400, was used for hard alloys such as refractory and Fe base glasses. The sliders used were surface finished by polishing with I4pdiamond paste. The wear tester employed in these experiments and shown in Figure 1 is of standard design. The normal load is provided by a dead weight of 0.15,O.75 Kg; the tangential (frictional) force is detected by a strain ring and displayed on a recorder. Each run takes from one half minute to 30 minutes depending on the normal load used for the test. Sample weight losses were measured with a Mettler M3 micro-balance having an accuracy of
RESULTS AND DISCUSSIONS For purposes of the present report, transition metal rich glassy alloys are conveniently classifi
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