Effect of crystal orientation on lapping and polishing processes of natural quartz

Lapping and polishing processes of natural quartz; are investigated in rela tion to crystallographic orientation and applied normal stress. Weight loss measurements and surface profilometry were carried out in X-, Y-, Z-, and AT-cut samples. The relationship found between material removal rate and st ress depends on specimen orientation. Based on indentation fracture mechani cs, this behavior is discussed in relation to fracture toughness and scratc h hardness anisotropy of quartz crystals. Scanning electron microscopy (SEM ) shows that brittle microcracking is the primary mechanism involved with m aterial removal in the lapping process. Plastic deformation mechanisms begi n to operate on lapped and polished surfaces above a certain Value of stres s. Surface profiles and SEM micrographs show that the roughness of lapped s urfaces decreases with increasing normal stress, but an opposite behavior i s observed in polished surfaces.