Effect of the Tool Composite Porosity on the Efficiency of Profile Diamond Grinding of Sapphire and Zirconium Dioxide
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STIGATION OF MACHINING PROCESSES
Effect of the Tool Composite Porosity on the Efficiency of Profile Diamond Grinding of Sapphire and Zirconium Dioxide Ye. O. Pashchenkoa, S. V. Sokhan’a, *, G. V. Sorochenkob, D. A. Savchenkoa, O. V. Lazhevskaa, S. V. Skorokhoda, and O. A. Mikishchenkoa aBakul
Institute of Superhard Materials, National Academy of Sciences of Ukraine, Kyiv, 04074 Ukraine b Bogomolets National Medical University, Kyiv, 01601 Ukraine *e-mail: [email protected] Received July 24, 2019; revised July 24, 2019; accepted July 25, 2019
Abstract—The efficiency of diamomd grinding of the sapphire and polycrystalline zirconium dioxide spherical surfaces with a diamond tool based on a metal binder with a reduced spread of porous inclusions in size is experimentally investigated. The tool composite is compacted using polyethylene glycol modified with adamantane derivatives, which increases the nonlinearity of the humidifier flow at the stage of briquetting. It is shown that the amplitude of the coefficient of friction decreases by a factor of 3 when such a composite is in friction with zirconium dioxide compared to sapphire friction. In addition, scratches are observed on the polished surface of sapphire in contrast to the case of grinding of zirconium dioxide, to exclude which it is advisable to make sure that the structure of the porous space of the composite has not only a certain size distribution of porous inclusions, but also a reduced value of their most probable size. The parameters of the relative productivity and wear of the diamond tool when grinding sapphire and zirconium dioxide differ by a factor of 2 to 3 depending on the grit size of the abrasive material. The surface roughness of polycrystalline zirconium dioxide upon its fine grinding is generally four to five times lower than that of sapphire. Keywords: tool composite, distribution of porous inclusions, sapphire, polycrystalline zirconia, spherical surface, precision diamond grinding, porosity structure, surface roughness DOI: 10.3103/S1063457620040073
INTRODUCTION At the present stage of development of medical equipment, there is an increased demand for products made of high quality materials, for which the accuracy of manufacture and surface quality are key factors that determine the duration of their service life [1]. Due to the large variety of shapes and sizes of such products, as well as relatively small volumes of production in most cases, high-precision machining centers can perform complex technological transitions and, at the same time, have high flexibility are best suited for their production [2–4]. Diamond grinding is traditionally used to obtain medical products from sapphire and polycrystalline zirconia [4]. In the case of grinding spherical or complex-profile surfaces of ceramic prostheses of heads of joints and other implants made of these intractable materials with an accuracy of ≤1 μm, the problem is to ensure the required surface roughness of the product, which is characterized by parameter Ra = 0.01–0.02 μm [5]. Some physic
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