The Additive Pycnometric Method For Assessment of the Degree of Coating of Grinding Powders Made of Superhard Materials
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S, POWDERS, PASTES
The Additive Pycnometric Method for Assessment of the Degree of Coating of Grinding Powders Made of Superhard Materials Using the Extrapolation-Affine 3D-Model of the Grain G. A. Petasyuka, *, O. O. Bochechkaa, **, V. I. Lavrinenkoa, V. G. Poltoratskyia, V. P. Bilochenkoa, and D. V. Sokolyuka aBakul
Institute for Superhard Materials, National Academy of Sciences of Ukraine, Kyiv, 04074 Ukraine *e-mail: [email protected] **e-mail: [email protected] Received April 5, 2019; revised November 21, 2019; accepted November 29, 2019
Abstract—The methodical components of determining the degree of coating of synthetic diamond grinding powders have been analyzed. The limitations of the most common weighing method, which make it unsuitable in the case of some coating techniques, are noted. The additive pycnometric method, in which the extrapolation-affine 3D-model of the grain and additional sieve separation are used, is proposed as an alternative to the weighing method. The results of using the new method for the assessment of the degree of coating of synthetic diamond grinding powders with boron oxide and tungsten are presented. Keywords: coating, degree of coating, volume, grinding powder, 3D grain model, pycnometric ratio, additive property DOI: 10.3103/S1063457620030077
Coating is an efficient method of modifying the grain surface of powdered synthetic diamond (SD), cubic boron nitride (cBN), and abrasive powders of other superhard materials (SHMs) [1]. The main purpose of this technological operation is to increase the efficiency of the use of abrasive tools that contain coated grains of abrasive powders. Metals (nickel, cobalt, titanium, tungsten, and others) are most often used as coating materials. According to the terminology established in the field of SHM abrasive powders, coating with these materials is called metallization, and the modified powders are known as metallized. Electrochemical deposition, chemical reduction, diffusion application from the vapor-gas phase, and sputtering in vacuum are the best-known methods of SHM powder metallization [1–4]. Liquid-phase coating is a relatively new method for performing grain surface modification on SHM powders [5]. Grain coating thickness is an important quality parameter of metallized SHM grinding powders. It is a fundamental factor (along with coating uniformity) that determines the cohesion strength of the powder grains in the cutting layer of the abrasive tool, and, consequently, the specific consumption of the abrasive powder. The set of initial data required for the assessment of coating thickness of SHM abrasive powder by the known methods [6] includes μ, the degree of coating (or the degree of metallization if the coating material is a metal). By definition, [1]
mca − ma (1) × 100, ma where ma and mca is the grinding powder weight before and after the coating of the grains. Let us note that this weighing method of determining the degree of coating can be unconditionally applied only to certain methods of coating, in particular to the el
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