ビッカース圧子によるサファイア単結晶の（０００１）および（１０￣１０）面での破壊と変形

Abstract

Abrasive wear on the contacting surface of machine elements proceeds via penetration or scratch of the sharp asperity tips or wear debris. In order to elucidate the mechanism of wear, it is firstly necessary to have knowledge on the microscopic deformations such as dislocations, minute cracks and slips induced by such penetrations. In the present study, indentation tests using a Vickers indenter were carried out on the (0001) and (1010) crystal faces of Sapphire (Al2O3) single crystals.The diagonal of an indenter was oriented in two ways: parallel and 45° against the [1010] direction on the (0001) face, and against the [0001] direction on the (1010) face respectively. The cleaving faces and directions of propagation of the cracks around an indent were estimated. In addition the shape and distributions of etch pits around an indent were examined.The results obtained are summarized as follows:(1) Radial cracks originate in four directions under comparative lower load of 5.0N, and in six directions under higher load of 10.0N on both of the (0001) and (1010) faces. Raptures that form connections with these cracks are also observed.(2) An average length of cracks on the (0001) is longer about 20% in 0° indentation than that in 45° indentation.(3) Cracks and edges of an indent are formed in a curved pattern due to the anisotropic crystal deformation.(4) Twinnings are observed on the (1010) in both 0° and 45° indentations.(5) Noticeable difference in size of indent was not confirmed in 0° between 45° indentation. An average length of the cracks on the (1010) is about 2.0 times as long as that on the (0001).(6) The area around an indent on the (1010) is corroded by etching in similar figure to individual etch pit.