SURFACE-ROUGHNESS ANALYSIS OF GLASS-CERAMIC SUBSTRATES AND FINISHED MAGNETIC DISKS, AND NI-P COATED AL-MG AND GLASS SUBSTRATES

Surface roughness measurements were performed on two types of glass-ce ramic substrates (GC(1), GC,) and corresponding finished magnetic disk s (GC(1f), GC(2f)), Ni-P coated Al-Mg substrate (Ni-P) and glass subst rate (Gl) by atomic force microscope (AFM), stylus profiler (SP) and n on-contact optical profiler (NOP) for different scan sizes and samplin g intervals. Results of surface roughness of different substrates and finished disks are presented with the following objectives to show (i) the differences between various substrates, (ii) the differences betw een substrate and the corresponding finished disk, (iii) the differenc es between SP, Am? and NOP measurements, (iv) the effects of scan size and sampling interval. Comments of different instruments for surface roughness measurement are given. The methodology of choosing the scan size and sampling interval suggested by Poon and Bhushan (Wear, in pre ss) is used to define the suitable scan size and sampling interval for various samples. The surface measurements of GC(1), GC(2), GC(1f), GC (2f), Ni-P and Gl samples are analyzed and extended to explore the pos sibility of relating the tribological parameters such as peak height, peak curvature, profile slope and peak density in terms of basic param eters such as the standard deviation of profile heights a and the corr elation length beta by the approach of Whitehouse and Archard (Proc. R. Sec. London, Ser. A, 316 (1970) 97-121) or spectral moments m(0), m (2) and m(4) by the approach of Nayak (J. Lubr. Technol. Trans. ASME, 93F, (1971) 398-407). It is concluded that all the tribological parame ters being studied can be related to sigma, beta or m(0), m(2) and m( 4) which in turns can be used to relate the tribological performance o f a surface. For low-flying magnetic storage devices, measurement of p eak-to-mean is also recommended.