Papers by Keyword: Alloy

Abstract: In this paper, the effect of sprayed coating on the surface of carbon steel on friction and abrasion properties of oil seals which are rubbed by various anti-wear coating materials on is investigated experimentally, and compared with the uncoated AISI 52100 bearing steel. We used the block vs ring tester to explore the friction coefficient of hard surface friction of 5 commonly used rubber seal to 4 different coating layers of bearing steel under oil/no oil conditions. Four coating materials are used, which are Ni-Cr-B-Si alloy, Ni-Cr-WC alloy, ceramics, and ceramics. Five varieties of the oil seal material named HNBR, NBR, FKM, ACM, and SIL are subjected to wear tests for the measurements of friction and abrasion. The experimental results show that HNBR has better wear resistance and less friction, ceramics have higher friction and wear resistance than other coatings due to higher hardness. In terms of oil seal and sprayed coating, Ni-Cr-B-Si alloy and ceramic powder are more suitable for surface wear resistance, because of its hardness and wear resistance and the degree of damage to the oil seal are more excellent. Generally, the greater the wear resistance of the oil seal material, the greater its friction with the coating.

Abstract: This report outlines a succinct analysis of the contemporary casting methods in single-crystal turbine blades. Furthermore, this paper also provides an examination of the solidification procedure in mixed turbine blades. The couple cooling and heating operation system was advanced to obtain identical thermal positions for single crystal (SC) solidification in the blade group, thereby significantly diminishing the associated flaws in the contemporary Bridgman process. The chemistry science of Nickel based alloys planed for single crystal (SC) gas turbine blades has been notably improved upon, especially when considering the initial production of alloys. The second and third production within the total operation has been enhanced by the introduction of rhenium (Re). Surged density, grain flaws, and microstructural stableness have presented themselves as significant issues within this process. Additionally, it is imperative to minimize the concentrations of the different alloying components.

Abstract: In this research paper, two different metal plates of aluminum alloy viz. AA6061 and AA6101 were welded with friction stir welding process. Round tool and square tool pin profiles were used to weld the alloys. Weld microstructures, hardness, and tensile properties were evaluated in as-welded condition. The tensile strength of the joints fabricated with round tool pin profile were lower than the square tool pin profile because of the pulsating effect, in square tool pin profile this effect was produced along with the higher frictional forces. The micro-hardness of friction stir zone was higher than the base material due to active recrystallization occurrence which resulted in fine grain size in case of weld joint with round pin profile. Microstructure indicated uniformly distribution of materials with minimum heat affected zone and dense welded zone without any defects.

Abstract: Heat resistant cobalt-based alloys have found a specific niche in the present-day mechanical engineering due to their unique properties. To begin with, cobalt-based alloys are used as corrosion, heat and wear resistant materials intended for aggressive environments and operation at extreme temperatures, e.g. blades, nozzles, swirlers, rings and other elements of turbines and internal combustion engines. Traditional molding methods applied in the mechanical engineering fail to provide necessary operational and technological characteristics of aforementioned machine parts. Owing to selective laser melting it is possible to reduce a production time and manufacturing costs for machine elements with a complex physical configuration and generate an alloy with an extraordinary structure, which is not found in traditionally combined compounds. A structure of cobalt exists in two crystal modifications: a hexagonal close-packed epsilon phase, a low-temperature phase and a face-centered cubic lattice gamma phase, a high-temperature phase. The alloy hardness is directly related to an amount of a low-temperature phase. The laser melting shortens a laser beam impact time on a powder composition due to a higher power and laser travelling speed. A high value of heat conductivity seems to be the reason for rapid solidification and cooling, which, in their turn, increase a percent of an alpha-martensite phase in an alloy and improve the hardness and wear resistance of machine parts. The reported paper summarizes studies aimed at the development of a stable phase structure three-component alloy (Сo-66 mass % Cr-6 mass % Mo) based on the cobalt-chromium-molybdenum system and mixed up via selective laser melting.

Abstract: Established the possibility of galvanochemical obtaining of a plating stronger than in case of chrome precipitation. Proposed precipitation of ternary alloy Co-Мо-W, which allows using the effect of synergism. Proposed and researched usage instead of sulphate-anhydride electrolyte – citrate-diphosphate and ammonia-citrate one. Achieved an increase in current efficiency of precipitated alloy and decrease in current efficiency of hydrogen, with respect to chrome precipitation, which increased safety of the galvanochemical industry. Selected the optimal ratios of components in citrate-diphosphate and ammonia-citrate electrolytes for ternary alloy Co-Мо-W precipitation. Determined the parameters of electrical effect for the galvanic process: constant current – j = 2–8 А/dm², pulse unipolar current – j = 4–20 А/дм². Achieved a high microhardness of this plating and high adhesion to base surface. Achieved greater safety of the galvanochemical technological process of ternary alloy Co-Мо-W application compared with chromium plating.

Abstract: The oxidation behaviors of tantalum-tungsten alloy with 10-20% W was investigated between temperature range of 700 to 900 °C exposed in air. The kinetics of Ta-W alloy was determined by TG-DTA, the characteristics of oxides were analyzed by SEM, EDS and XRD. The oxidation tests revealed that the alloys obeyed parabolic kinetic in the initial stage, then translated in linear law. The addition of W has a good effect on the oxidation resistance of Ta-W alloys at experimental temperature. Solid solution of Ta₂O₅ form in case of oxidation product of Ta-10W, Ta-15W alloys, while the complex oxide Ta₂₂W₄O₆₇ form after Ta-20W alloy oxidized. The formation of solid solution and complex oxide impeded the volatilization. The compact oxide film protects the penetration of oxygen in the initial oxidation stage. The large compressive stresses and mismatch of the coefficient of thermal expansion between oxide scale and matrix alloys make the oxides layer be broken, which cause kinetic of oxidization obeying linear law.

Abstract: The research assesses the possibilities of using local minerals to create foundry alloys that are used in conditions of low temperature. The mineral-geochemical composition of iron ore from Verkhnyaya Amga ore occurrences in the Aldan region of the Sakha Republic (Yakutia) was studied in detail. The expedience of using iron ores from this ore occurrence to develop new cold-resistant and high-strength steels was analyzed. The chemical composition and microstructure of the cast alloys were studied. The ore contains oxides of alkaline earth metals: MgO; CaO; Sr0 and BaO, the total content of which is 4.2%, that contributes to the process of deoxidation of the melt during its cooling, and the deoxidation product in the form of oxides and other chemical compounds based on Ca, Sr and Ba floats into slag. During crystallization, the melt is cleaned of detrimental impurities, non-metallic inclusions, gases, pores, etc. Alloy is smelted from enriched ore, samples for static tension and toughness are made in order to study the physicomechanical properties. Microstructure of the obtained alloy and structural steel subjected to static tension at an external load of 0.8 yield strength (σ = 0,8 σ_т) was investigated. Mechanical properties and dynamic characteristics were measured. Analogues for comparing the strength and plastic properties were given.

Abstract: Biodegradable vascular stent is mainly made of materials that can be naturally decomposed. Magnesium and its alloys have excellent mechanical properties and biocompatibility. The vascular stent made of magnesium and its alloys has the unique advantages of strength of metal scaffolds and bioabsorbability of degradable polymer scaffolds. Due to the special microenvironment inside the blood vessels, the stent should have good resistance against corrosion. After implantation of metal materials for human tissue repair, the surface oxidation film spontaneously formed in the air will react with the human physiological environment. The nature of the interface between materials and tissues will have a certain impact on the corrosion resistance of metals and the degree of metal ion release, thus determining the biocompatibility of materials.

Abstract: The problem of enrichment and dephosphorization of poor manganese ores for receiving the low-phosphorous alloys necessary for smelting of steel of low-temperature reliability is considered.

Abstract: This paperwork presents the results of a series of experiments on the use of homogenizing annealing, aimed at the possibility to control the structure and properties of steel samples obtained by aluminothermy. This method of processing, in some cases, allows to eliminate the need to use subsequent heat treatment operations due to the achievement of the required properties by the cast blank material. Refractory materials and thermite mixtures used, conditions for the production of castings and their total chemical composition are given. The tensile diagram analysis of the samples before and after heat treatment is presented; the structures and diffraction patterns of the samples’ destruction spots are considered. The material obtained by aluminothermy corresponds in its chemical composition to A1, A2, A3, A4 grade of steels for the rail transport according to GOST 31334-2007 which are used in the manufacture of locomotive axes and other rolling stock.