Production of gradient ultrafine-grained hard alloys from powders obtained from scrap VK15 alloy dispersed in water and scrap VK8 alloy dispersed in oil

An experiment has been carried out aimed at producing a low-cost tool material which would have an extra hard surface and a crack resistant base phase. A double-layer gradient alloy was produced out of powders with excessive and insufficient carbon obtained from alloys VK8 and VK15 by electrospark dispersion. To obtain the initial powder, plates of the VK8 alloy scrap material initially containing 5.6% of carbon were dispersed in oil. This caused excessive carbon (3.1%), which was then partially reduced to 0.6% by CO2 heat treatment. The VK15 alloy with 5.3% of initial carbon was dispersed in water to achieve an insufficient carbon concentration (2.8 %) in it. It was then heat treated in the CO atmosphere to partially lower the carbon concentration to 0.7%. The dispersed powder was found to consist of spherical microparticles, as well as agglomerated nanoparticles obtained through crystallization of liquid and vapour phases. Mixing of tungsten and cobalt phases resulted in much smaller diameters of WC grains in the newly sintered alloy. This combination of deviations in the carbon concentration between the layers helped maintain the unequal concentration of cobalt (8 and 15%) and thus ensure an extra hard surface (1820HV) and a crack resistant base (14.2 MPa√m). Analysis was carried out to estimate the power costs, as well as the performance of the laboratory unit used for electrospark dispersion of hard alloys.

EFFECTIVE APPROACH TO WATER PURIFICATION FROM MICROBIOLOGICAL CONTAMINATION BASED ON NOVEL SURFACE-MODIFIED ADSORBENTS

In this work, we provide a literature review of water treatment techniques and propose a novel resource-efficient solution for the purification of aqueous media from microbiological contamination. Methods: Combined filter sorbents were developed and studied based on novel modified nanostructured filter materials. Synthetic and natural zeolite were used as the mineral base. The production technique was optimized to coat minerals with aluminum oxyhydroxide by means of a sol–gel process. Additional treatment with fine zinc particles obtained by electrospark dispersion was applied to modify the sorbent surface and obtain the surface charge required. Results: The antibacterial, sorption and physicochemical properties of the samples as well as their surface structures were investigated. According to broad microbiological tests, the possibility of purifying bacterial-contaminated water was demonstrated to an acceptable level by means of adsorption filtration. Conclusion: The proposed novel approach for water treatment against bacterial contamination can be considered an alternative to the currently available water treatment technologies.

Study of Products of Metallic Titanium Electrospark Dispersion in Aqueous Medium

The results of electrospark dispersion of the metallic titanium loading in aqueous medium are presented in the paper. Raster electronic microscopy, X-ray phase analysis and BET method were used to investigate properties of the obtained powder. Values of specific surface are given in the paper, and morphology and structure of the obtained powders are studied. It is established that chemical and phase composition of the obtained powders is identified by properties of the molten titanium to interact with the dissolved in dispersion medium gaseous products.