Influence of Steel Surface Composition on ZDDP Tribofilm Growth Using Ion Implantation

This paper examines the influence of steel surface composition on antiwear tribofilm formation by ion-implanting typical steel alloying elements, Ni, Mo, Cr, V and W, into AISI 52100 bearing steel surfaces. Such implantation changes the chemical composition of the steel surface but has relatively little effect on its mechanical properties or topography. The behaviour of zinc dialkyldithiophosphate (ZDDP) antiwear additive was studied. The study employs a ball on disc tribometer with ability to monitor tribofilm development and a range of analytical tools including STEM-EDX, XPS and FIB-TEM to analyse the formed tribofilms. It was found that Ni implantation promotes ZDDP tribofilm formation while Mo and Cr implantation deters tribofilm growth. V and W implantation do not significantly change tribofilm formation. Results on the influence of ZDDP concentration on tribofilm formation rate with different implanted metals suggest that one important mechanism by which steel composition influences tribofilm formation may be by controlling the extent of ZDDP adsorption. This study shows the importance of steel surface composition on ZDDP response and also demonstrates a powerful way to study and potentially improve the tribological performance of machine components via a combination of lubricant formulation and surface modification.

Study of rail steel alloying by chrome and vanadium effect on dissociation of overcooled austenite

To determine weldability and quality of a rail welded joint, information on kinetics of the rail steel overcooled austenite transformation is high importance. Thermo-kinetic diagrams of overcooled austenite dissociation of steels Э76ХФ, Э76ХАФ and Э76Ф, built based on results of dilatometric, metal science and durometric tests of rail steel samples. It was shown, that increase of chrome content in steels Э76Ф and Э76ХФ composition from 0.09 to 0.39% results in expanding of dissociation area of overcooled austenite at temperature scale for ferrite-cementite mixture and increasing of resistivity of the overcooled austenite against dissociation in the area of ferrite-cementite mixture formation. This can be characterized as decrease of critical quenching velocity from 100 to 30 °С/sec. It enables to obtain structural states of higher hardness at cooling with velocities in the area of 0.1−30 °С/sec. It was established, that increase of vanadium content from 0.04 to 0.07% does not cause quality changes at the thermo-kinetic diagram of overcooled austenite dissociation. However, it known, that vanadium is a strong carbide-formation element, which combines with carbon at low cooling velocities and removes it out of the solid solution. Due to this effect, sample of steel Э76ХФ with lower vanadium content at cooling with velocities from 0.1 to 10 °С/sec, had somewhat higher hardness level comparing with steel Э76ХАФ sample. Increase of chrome content in alloy content results in an increase of temperature of austenite formation completion at heating from 760 to 774 °С, while the temperature of martensitic transformation commencement at that remains practically unchanged at the level of 230 °С. In steels Э76ХФ and Э76ХАФ in the chemistry of which chrome was added in the amount of 0.37−0.39%, after cooling with velocities of 1 °С/sec and lower, apart from ferrite-carbide mixture of perlite type, formation of redundant ferrite with a volume share of 4−5% was observed as a result of overcooled austenite dissociation. However, in a steel Э76Ф sample, the content of which has chrome at the level of 0.09% at close content of carbon, after cooling in an analogue range of velocities, a ferritecarbide mixture of perlite type is formed with a slight trace of redundant ferrite in the structure as a result of overcooled austenite dissociation.

Characterization of ultrafine particles emitted during laser-based additive manufacturing of metal parts

Particulate matter (PM) emitted during laser additive manufacturing with stainless steel powder materials has been studied in detail. Three different additive manufacturing techniques were studied: selective laser melting, direct metal deposition and laser cladding. Gas flow and temperature fields accompanying the processes were numerically modeled for understanding particle growth and oxidation. Transmission and scanning electron microscopy were used for primary particle and PM characterization. The PM collected in the atmosphere during manufacturing consisted of complex aggregates/agglomerates with fractal-like geometries. The overwhelming number of particles formed in the three processes had equivalent projected area diameters within the 4–16 nm size range, with median sizes of 8.0, 9.4 and 11.2 nm. The primary particles were spherical in shape and consisted of oxides of the main steel alloying elements. Larger primary particles (> 30 nm) were not fully oxidized, but where characterized by a metallic core and an oxidic surface shell.

A possibility of using nickel concentrate, obtained as a result of hydrometallurgical enrichment of manganese-containing raw materials, at steel alloying

At production of stainless steel expensive alloying elements, containing nickel, are used. To decrease the steel cost, substitution of nickel during steel alloying process by its oxides is an actual task. Results of analysis of thermodynamic and experimental studies of nickel reducing from its oxide presented, as well as methods of nickel oxide obtaining at manganese bearing complex raw materials enrichment and practice of its application during steel alloying. Technology of comprehensive processing of complex manganese-containing raw materials considered, including leaching and selective extraction out of the solution valuable components: manganese, nickel, iron, cobalt and copper. Based on theoretical and experiment studies, a possibility of substitution of metal nickel by concentrates, obtained as a result of hydrometallurgical enrichment, was confirmed. Optimal technological parameters, ensuring high degree of nickel recovery out of the initial raw materials were determined. It was established, that for direct steel alloying it is reasonable to add into the charge pellets, consisting of nickel concentrate and coke fines, that enables to reach the through nickel recovery at a level of 90%. The proposed method of alloying steel by nickel gives a possibility to decrease considerably steel cost at the expense of application of nickel concentrate, obtained out of tails of hydrometallurgical enrichment of manganese-bearing raw materials, which is much cheaper comparing with the metal nickel.

Analysis of the use of rare earth metals in ferrous metallurgy of Russia and world

The analysis of the current state of production of rare earth metals (REM) in Russia and in the world was made. Information about REM production in different countries of the world and about new foreign projects for REM production and processing is provided. The article presents the balance of production, export and import of raw materials and products with REM, including scandium and yttrium, in Russia. The maximum volume of REM consumption in Russia was calculated taking into account imported products with REM. This data was compared with other countries, including the former USSR. Much attention is paid to the use of REM in metallurgy. Data on the influence of REM on the properties of cast iron and steel are presented. Information is given about the forms of REM used for their use in the Russian ferrous metallurgy. We have studied the structure of REM consumption in ferrous and non-ferrous metallurgy. On the example of two enterprises (one of them specializes in mass production, and the second – on production of special steels), the structure of REM consumption for steel alloying was studied by type and scope of its application. The development peculiarities of REM consumption in Russian ferrous metallurgy were investigated. The volume of consumption was calculated; data on imports of raw materials with REM for metallurgy and the producers of ferroalloys with REM in Russia is given. We have analyzed the spectrum of steel products with REM. A comparison of the consumption of REM in the metallurgy of Russia and foreign countries is presented. The reasons for insufficient consumption of REM in the Russian metallurgy are considered, an assessment is given on the change in production volumes of certain types of steel and cast iron, and recommendations are made on the growth of REM consumption in metallurgy.

Resource-Saving Technologies in Production Cold-Resistant Steels

The possibility of application for steel alloying with vanadium of the technology based on restoration of vanadium from oxides of converter vanadic slag with use of the reducers (carbon of a koksik and silicon of ferrosilicium) having low cost and a purge gaseous nitrogen with high coefficient of extraction of the alloying element is shown.

Peculiarities of application of natural and man-caused materials for steel alloying and modifying

Considerable reserves of improvement of steel quality and reduction of costs of its production are concealed in a possibility of active and purposeful formation their structure and the properties by introduction into the melt modifiers, alloying and microalloying additives. Due to the task of decreasing costs, studies on alloying and modifying of metal by natural and man-caused materials are very actual. Thermodynamic regularities of steel alloying and modifying processes by natural and man-caused materials, including manganese ores of various structures, BOF vanadium slag, barium- strontium modifier, obtained from the complex ores containing barium and strontium considered. Possibilities of wide application of various structure manganese ores for steel alloying by manganese without use of standard manganese alloys as well as vanadium slag for microalloying by vanadium demonstrated. Metallurgical properties barium-strontium natural modifier obtained and the possible mechanism of the modifying impact of barium and strontium on quality of metal studied. It was determined, that the effect of modifying by barium can revealed in steels, deoxidized only by silicon, and for modifying by strontium or joint modifying by barium and strontium it is necessary to apply aluminum as deoxidizing agent. Industrial testing of the above-stated materials showed reliability of studies, accomplished at thermodynamic modeling and laboratory studies of calculations and conclusions. Recommendations on optimization of technologies of steel alloying and modifying made. It was proved that use of the materials of the study allows to improve technical and economic indices of the process of production of steels and to increase considerably quality of final steel products. Conclusions on significant expansion of natural and man-caused materials prospects worded.

Mastering of production of lead-free ecologically clean free-machining steels

Both in the domestic and world steel industry alternative ecologically clean free-cutting steels, having cutting machinability characteristics and mechanicalproperties, comparable with lead-containing steels, but voided of their drawbacks,are actively searched. First ofall the alternative steels should not be not so ecologically harmful. Scientific and technological aspects of lead-free free-machining steels production, alloyed by bismuth, calcium, tin, boron and nitrogen presented. Solubility of bismuth in iron and iron alloys with chromium, manganese, nickel, tungsten, vanadium, cobalt,phosphor, sulphur, aluminum, carbon and other elements at the temperature of 1550–1650 ºСdetermined. Parameters of interaction of the first and second order calculated. Study of bismuth behavior and tin spherical samples in 40X steel melt accomplished. The study done at the high temperature facility with controlled atmosphere and X-ray TV observation system. Simulation of phase compositions multicomponent alloys of steel АВЦ40ХГНМaccomplished by application of a program package FactSage. Within the study,a production technology of lead-free, ecologically clean free-machining, steels elaborated and masteredat OJSC “Zlatoust electro-metallurgical works”. Free-machining corrosion-resistant steels (АВЦ19ХГН, АВЦ40Х, АВЦ40ХГНМ, АВЦ12Х18Н10, АВЦ40Х13, АВЦ14Х17Н2) alloyed by bismuth and calcium, steels (АО40Х, АО30ХМ) alloyed by tin, and steels (А38ХГМАРand А30ХМАР) containing BN were the objects of the study. The steels samples were in the form of forged billet of 10, 20 and 80 mm diameter and ingots of 18 and 500 kg (round 345 mm). Steel quality characteristics determined such as mechanicalproperties in longitudinal and cross directions of ingots, uniformity of distribution of fusible elements, carbon and Sulphur along the axis zone and in billet transverse sections. Pictures of ingots macrostructure by height and section obtained. Estimation of hardenability and steel contamination by non-metallic inclusions, austenitic grain size, steel machinability by cutting, surfacequality of re-worked billet and steel macrostructure accomplished. Comparable ecological studies of atmosphere contamination during the steel alloying also accomplished.