Polishing: Mechanically Induced Degradation of Diamond

Abstract

In this paper, a simple concept is proposed for the development of a model which describes the well‐known highly anisotropic behaviour of diamond as observed during conventional polishing. In the view of recently obtained results, a simple mechanism involving a mechanically induced local transformation from sp3 to sp2 hybridised carbon is considered.

Investigating the mechanisms of diamond polishing using Raman spectroscopy

“…The presence of amorphous carbon in the ejected material is also due to reciprocal polishing of the workpiece and the scaife, and later during polishing of diamond. A plausible route by which this conversion may happen is via a mechanical transformation of the diamond by the large shear forces at the diamond-scaife interface as proposed by van Bouwelen et al [19,27]. However, the presence of iron in all debris perhaps indicates that the process may not be as simple as this and could involve a chemical wear component.…”

“…Polishing mechanisms are discussed here; for a review of the origins of diamond friction and associated wear debris the reader is referred to [26]. The two most plausible mechanisms of wear during polishing considered to-date are thermally based [5] or mechano-chemical [19,27]. Thermal wear has previously been dismissed due to reports [22] that material removal was linearly proportional to the abrading (NB: not polishing) velocity.…”

“…These experiments were not carried out under industrial polishing conditions, rather on miniature grinding wheels and more recent research [3,4,17] challenges their view. van Bouwelen et al [27] suggest that a structural change due to the large shear stresses present at the diamond-scaife interface is responsible for the non-diamond carbon wear debris. This mechanism is attractive since it explains both the extraordinary tribological anisotropy and the associated wear debris, in terms of the crystallographic structure of diamond.…”

“…The answer lies in the conversion of both the diamond grits on the scaife, and the diamond components of the SYNDAX3 to amorphous carbon. This is another 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 F o r P e e r R e v i e w O n l y indication of the reciprocal polishing action between the grits on the scaife and the workpiece [3,27]. The silicone oil prepared scaife performed very poorly during use tending to score the diamond workpiece badly.…”

“…This is somewhat peculiar given diamond's oleophilic nature, and the amount of amorphous carbon material present on the scaife formed both during preparation and added to during polishing. If polishing does indeed proceed by a mechanically induced phase transformation [19,27] and wear rates are ca. 40 µm min -1 , the lack of a detectable film could be explained by a planing action of the scaife.…”