International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The influence of the vanadium, niobium and boron addition on properties of high-chromium white cast iron alloys for grinding balls is investigated in this paper. These alloying elements were individually added to the high-chromium white cast iron alloys with monitoring of changes in microstructure, corrosion rate, and mechanical properties in the as-cast conditions. The microstructure in all tested alloys consists of primary austenite dendrites and eutectic colonies, which consist of M7C3 carbides and austenite. The addition of V, Nb or B affects, to a greater or lesser extent, the size, morphology and volume fraction of both primary austenite dendrites and eutectic colonies. Samples of iron alloyed with vanadium and boron have a much finer structure than unmodified (base) alloy and niobium alloyed iron sample. Vanadium affects the decrease in the volume fraction of the primary austenitic phase, and the increase in the volume fraction of eutectic colonies, and thus the eutectic carbide phase in hypoeutectic alloys of high-chromium iron. The tested alloys have a comparable values of average hardness in the cross section of cast balls, as well as compressive yield strength, noting that the addition of vanadium increases the hardness, while boron addition increases the compressive yield stress. The single addition of all of three tested alloying elements shifts the corrosion potentials (and Tafel curves) of modified high-chromium white irons toward less negative values. The most favorable values of mechanical and corrosion properties were measured for the iron modified with 0.021 % of boron.

Heat-resistant composites with a layered niobium-based matrix reinforced with single-crystal sapphire fibers have been obtained. The fibers were grown from the melt by the modified Stepanov method. The composites were prepared by solid-phase technology by diffusion welding of multilayer packages of foils of the Nb–0.1% C and aluminum alloy, interlaid with sapphire fibers in layers of a suspension mixture of Nb powder. The production of fibers, their structure and strength testing procedure are described. The formation of multilayer packets, the structure and results of bending strength tests of composites are presented

The work is devoted to the development of a solid-phase technology for obtaining high-temperature layered composites from Nballoys. The following are presented: one of the options for the formation of the initial multilayer package and its diffusion welding (1), the microstructure of the obtained composites (2) and the results of testing composites (3) for strength at room temperature and temperatures up to 1350°C, taking into account the structure anisotropy, crack resistance and tests for creep with two options for processing the obtained experimental data.