metals Article Variation of Grain Height Characteristics of Electroplated cBN Grinding-Wheel Active Surfaces Associated with Their Wear Anna Bazan * , Andrzej Kawalec , Tomasz Rydzak and Pawel Kubik Faculty of Mechanical Engineering and Aeronautics, Rzeszow University of Technology, 35-959 Rzeszów, Poland; ak@prz.edu.pl (A.K.); t.rydzak@prz.edu.pl (T.R.); p.kubik@prz.edu.pl (P.K.) * Correspondence: abazan@prz.edu.pl; Tel.: +48-17-865-1371 Received: 14 September 2020; Accepted: 2 November 2020; Published: 6 November 2020   Abstract: During the operation of a single-layer grinding wheel (SLGW), irreversible changes occur on its active surface due to wear. The study of grinding-wheel microgeometry changes can be based on the measurement of the surface texture as well as the determination and analysis of its parameters. The article deals with the selection of suitable texture parameters and an appropriate mathematical model carrying information about the SLGW condition. In the study, samples of Pyrowear 53 steel were ground using electroplated cBN single-layer grinding wheels until they were completely worn out or removed assumed volume of the workpiece material. Each SLGW worked with constant process parameters. Among the 144 parameters tested, the highest sensitivity to changes in wheel active surfaces caused by wear was shown by the mean value of the mean island heights Zmean_m. In-depth research was conducted for Zmean_m and reduced peak height Spk. Compared to Spk, Zmean_m has proven to be a better measure of wear, especially when large areas of sticking occur. Moreover, the second-degree models linking Zmean_m and Spk to the process parameters and the specific material loss were better suited to the empirical data than the exponential models. Keywords: electroplated grinding wheel; grinding-wheel wear; grinding-wheel surface texture; regression models 1. Introduction In the middle of 20th century there were developed effective methods of fabrication, based on synthesis, of two abrasives which play an important role in abrasive machining of materials, i.e., polycrystalline diamond (PCD) and cubic boron nitride (cBN). Both abrasives have been shown to have significantly bigger hardness than other abrasives used before the development of PCD and cBN. For that reason they quickly became important machining materials applied, among other things, to making abrasive tools. One of the varieties of abrasive tools is single-layer grinding wheels with the cBN abrasive. Those grinding wheels have a single layer of abrasive grains, embedded on a metal core material and joined with that core material with a binder. That binder is usually made using a galvanic method, i.e., in the electroplating process. Electrolytic placement of a nickel-based binder enables manufacturing profile grinding wheels with big repeatability [1]. The profile of such kind of grinding wheel does not change significantly during its operation because its active surface (AS) contains a single layer of a super-hard abrasive material [2,3]. Moreover, strong structure of those grinding wheels enables both applications of high cutting speed while grinding [4–6] and removing large amounts of material from machined workpieces in a unit of time [2]. The immutability of grinding-wheel profile makes possible manufacturing products with high repeatability of high quality without the need for grinding-wheel dressing. Therefore, those grinding Metals 2020, 10, 1479; doi:10.3390/met10111479 www.mdpi.com/journal/metals