621.785;621.9.825.7 Samples of zirconium dodecaboride are obtained by means of arc and induction melting of a mixture of zirconium and boron powders. A solder for binding the zirconium dodecaboride to the steel holder of the tool is selected. It is established that cutting tools supplied with zirconium dodecaboride may be used in operations of finish turning of adhesive-active titanium alloys.

A. A. AdamovskiiUDC 621.762This paper reviews works on the use of transition-metal carbides and presents results of the author's own research on the abrasive machining of mechanical engineering materials. It is established that the properties of abrasive grains are primarily controlled by the abrasive nature and production process. It is shown that carbides of transition metals are efficient for use in abrasive tools (grinding disks, pastes for processing mechanical engineering parts from various materials).

621.785;621.9.825.7 Samples of zirconium dodecaboride are obtained by means of arc and induction melting of a mixture of zirconium and boron powders. A solder for binding the zirconium dodecaboride to the steel holder of the tool is selected. It is established that cutting tools supplied with zirconium dodecaboride may be used in operations of finish turning of adhesive-active titanium alloys.Among the different alloys of the zirconium C boron system, zirconium dodecaboride (ZrB 12 ) is known as a material possessing rather high abrasion properties. ZrB 12 may be used especially effectively in polishing titanium and titanium alloys [1,2]. Zirconium dodecaboride is produced by arc melting of a charge of prescribed composition. The ingot that has been formed in a crystallizer is crushed in order to obtain abrasive powders of different grain sizes. The abrasive disks that are produced from these powders have demonstrated not only a high degree of efficiency in the treatment of the titanium alloy VT-1 comparable with that of diamond disks of the same grain size, but also yield a significant decrease in the surface roughness of the worked part [3].In view of the high abrasive capacity of zirconium dodecaboride, it is of significant scientific and practical interest to study the possibility of creating on the base of zirconium dodecaboride, not only grinding tools, but also cutting tools. The goal is to apply these types of tools for turning titanium and titanium alloys, in view of the fact that articles made of these materials are now finding increasingly greater use. The possibility of creating a cutting tool with inserts provided with polycrystals of zirconium dodecaboride has been studied by analogy with the well-known technology of fabricating cutting tools with inserts provided with polycrystals of superhard materials [4,5].Rugged cutting elements of ZrB 12 have been fabricated using arc (type I) or induction (type II) melting. Arc melting of compacts from a mixture of powders of zirconium and boron of stoichiometric composition have been produced in a standard laboratory-scale furnace equipped with a copper water-cooled crystallizer and nonconsumable tungsten electrode in a purified argon medium. From the melting point (2082EC) to a temperature of around 1500EC the cooling rate amounted to roughly 400 deg/sec and was then gradually reduced to 150 deg/sec until the ingot had completely cooled down. Directed crystallization of the melt was achieved in a Kristall III induction plant following the formation of a fusion zone at a temperature corresponding to the phase diagram of Zr − B. Preliminarily sintered porous rod billets were used as the initial material for directed crystallization. The charge was in the form of a mixture of zirconium powder and powder of finely crystallized boron. The boron was taken in excess with respect to stoichiometry. The components of the charge were carefully mixed in a cavitation bath of an ultrasonic vibrator. Rods were compacted from the obtained mixture in a steel die pressur...