Specific features of nickel waste grinding in gaseous media

Abstract

Machining of metal parts generates metal waste in the amount of up to 30 % of the original product mass requiring proper disposal. The main recycling technology in the market involves briquetting, followed by remelting, which is quite energy intensive and has a number of disadvantages. This paper proposes an alternative metal waste recycling method based on mechanical grinding. The data in various studies suggest that gases may be rated as follows in terms of their effect on disintegration of metal powders: hydrogen > helium > argon > nitrogen > air. In terms of the efficiency of removing sorbed gases from metal powders, the sequence is as follows: nitrogen > hydrogen > helium > argon. The results of the study on their effects on nickel chips disintegration suggest the following order: air – nitrogen – helium – argon (for ball mill grinding) and air – helium – argon – nitrogen (for vibration mill grinding). When grinding in air, the metal is actively covered with an oxide film; this prevents the aggregation of particles, which is otherwise observed in inert media as a result of cold welding. The use of inert media in mechanical grinding helps reducing the oxygen content on the surface of particles and prevents oxidation. These materials are applicable in powder metallurgy, in particular, for additive manufacturing and for making various parts by sintering. In terms of preventing metal oxidation, we recommend using helium for high-intensity grinding and nitrogen for traditional ball grinding. It must, however, be taken into account that helium is a more expensive gas. The authors express their gratitude to the scientific consultant of the work, Doctor of Engineering Sciences V. A. Arsentyev.The study was carried out under the grant issued by the Russian Science Foundation (project No. 20-79-10125).