Addition Of Molybdenum Research Articles

Effect of molybdenum addition on mechanical properties of oriented bulk Fe2B crystal

Abstract

Effect of the nature of sulfur compounds on their reactivity in the oxidative desulfurization of hydrocarbon fuels with oxygen over a modified CuZnAlO catalyst

The reactivity of thiophene, dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), which are the representatives of the main classes of sulfur compounds that are the constituents of diesel fractions, was studied in the course of their oxidative desulfurization with oxygen on a CuO/ZnO/Al2O3 catalyst modified with boron and molybdenum additives. At T ≥ 375°C, the reactivity increased in the order thiophene < DBT < 4,6-DMDBT. The degree of sulfur removal in the form of SO2 from hydrocarbon fuel, which was simulated by a solution of 4,6-DMDBT in toluene, was 80%. Under the assumption of a first order reaction with respect to sulfur compound and oxygen, the apparent activation energies of the test processes were calculated. An attempt was made to reveal the role of the adsorption of sulfur compounds in the overall process of oxidative desulfurization with the use of X-ray diffraction analysis, X-ray photoelectron spectroscopy, and differential thermal and thermogravimetric analysis with the massspectrometric monitoring of gas phase composition.

Effect of Molybdenum Additions on the Structurization of Fe–Mo Alloys and Contact Interaction in the TiB2–(Fe–Mo) Systems

The structurization of Fe–Mo alloys at 5–30 wt.% Mo is studied and contact interaction of these alloys with titanium diboride is examined. The Fe–5 wt.% Mo and Fe–9 wt.% Mo alloys consist of an α-Fe metallic structure with inclusions of Fe2Mo intermetallics. The Fe–13% Mo alloy based on the α-Fe solid solution contains individual inclusions of Fe3Mo2 intermetallics. When Mo content of the alloys increases to 17–30 wt.%, Fe2Mo and Fe3Mo2 intermetallics form intensively and make the alloy brittle. Zero contact angles are observed for the (Fe–13 wt.% Mo) and (Fe–17 wt.% Mo) alloys. The TiB2–(Fe–13 wt.% Mo) system is characterized by chemical interaction leading to additional molybdenum, iron, and titanium boride phases. The TiB2–(Fe–13 wt.% Mo) system shows no brittle intermetallic phases. The contact interaction in the TiB2–(Fe–17 wt.% Mo) system leads to the intensive formation of complex molybdenum–iron–titanium borides; there is also a great number of Fe3Mo2 intermetallics. The TiB2–(Fe–13 wt.% Mo) system is promising for the development of new composite materials and coatings with high wear resistance.

Synthesis and microstructure characterization of nanocrystalline NiAl intermetallic compound with molybdenum additions obtained by mechanical alloying

Nanocrystalline Ni50 Al50−x Mox (X = 0 and 5 at.%) intermetallic powders were synthesized by mechanical alloying (MA) in a planetary ball mill. Microstructural characterization and structural changes of powder particles during mechanical alloying were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results confirmed that the synthesis behavior of NiAl intermetallic depends on the milling time and Mo content. The mechanical alloyed powders have a microstructure consisting of nanometer size particles. Mo enhance has a considerable effect on the lowering of crystallite size. The TEM image showed that the Ni50 Al45 Mo5 nano-particles were less than 10 nm.

Effect of molybdenum addition on microstructure and mechanical properties of plain carbon steel weld

The present investigation has two main objectives; first is optimization of welding process parameters of submerged arc welding (SAW) using Taguchi philosophy and second is to improve the mechanical properties such as strength and microhardness of weld joint by alloying with varying amounts of molybdenum. For optimization of welding process, parameters Taguchi philosophy have been applied on a mild steel plate (AISI C- 1020) of 10 mm thickness with 60o groove angle with arc voltage and welding speed as variables and bead width as output variables. A mathematical relationship between bead width, arc voltage and welding speed has also been found using multiple regression analysis for the present base metal plate geometry. After optimizing welding parameters, molybdenum has been added individually to the welding area in varying percentages. The properties of alloyed and unalloyed weld metal bead are compared. The mechanical characterization of weld has been done in terms of microhardness, tensile strength, whereas microstructural characterization has been performed using optical microscopy, XRD and EDS. The presence of molybdenum resulted in bainite structure in weld bead having a refined grain structure, enhancement in tensile strength and microhardness. The XRD results showed the formation of molybdenum carbides justifying the increase in microhardness value.

Crystal structure and bonding characteristics of transformation products of bcc β in Ti-Mo alloys

Abstract Rietveld analysis of X-ray diffraction patterns of α′, α″ and β phases of four alloys of Ti-Mo has been carried out to refine their crystal structures and understand their nature of bonding. The addition of molybdenum to titanium is found to shift the stability of crystal structure from hcp to orthorhombic to bcc, as expected. The unit cell dimensions and the atomic positions of α′, α″ and β phases were evaluated, with excellent reliability indices. The reduction in unit cell dimensions and its volume, bond length and co-ordination number with addition of molybdenum is consistent with the reduced size of solute atom. The orthorhombic α″ phase, a transition phase with a minor distortion of hcp α′, is found to be closer to α′ than β phase, based on the orthorhombicity (b/a) and the volume of equivalent orthorhombic unit cells of the phases and the atomic shuffle y in 4c Wyckoff positions along b axis of α″ phase. The Fourier electron density contour maps suggest that the bonding in all phases is predominantly metallic. However, addition of molybdenum delocalizes the spatial distribution of charge density, suggesting an enhancement of metallic character. Anisotropy in charge density was observed along 〈011〉 and 〈010〉 in (100), 〈101〉 and 〈001〉 in (010) and 〈110〉 and 〈010〉 in (001) plane. This offers direct evidence for the origin of anisotropy in the values of elastic constants, reported in literature.

Effect of Alloying with Molybdenum and Chromium on Pipe Steel of Strength Category X65 Properties

Kinetics of austenite phase transformation in previously deformed steels of different alloy systems during continuous cooling are studied. It is shown that with a basic chemical composition of 0.06% C and 1.55% Mn–Nb–Ti alloying with chromium (0.19%) leads to the formation after cooling of an almost identical microstructure, as also with addition of molybdenum (0.14%), from the point of view of fineness and hardness. An optimum steel alloy system is suggested from an economic point of view that provides the required set of properties for rolled sheet more than 30 mm thick of strength category X65 produced under conditions of the VMZ (Vyksa) sheet rolling complex (5000 mill).

Corrosion behavior of construction materials for ionic liquid hydrogen compressor

The corrosion behavior of various commercially available stainless steels and nickel-based alloys as possible construction materials for components which are in direct contact with one of five different ionic liquids was evaluated. The ionic liquids, namely: 1-ethyl-3-methylimidazolium triflate, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide, butyltrimethylammonium bis (trifluoromethylsulfonyl) imide, methyltrioctylammonium bis (trifluoromethylsulfonyl) imide have been identified, as performance fluids in an ionic liquid hydrogen compressor. An electrochemical cell was specially designed, and steady-state cyclic voltammetry was used to measure the corrosion resistance of the alloys in the ionic liquids at 23 °C, under atmospheric pressure.The results showed a very high corrosion resistance and high stability for all the alloys tested. The two stainless steels, AISI 316L and AISI 347 showed higher corrosion resistance compared to AISI 321 in all the ionic liquids tested. It was observed that small addition of molybdenum, tantalum, and niobium to the alloys increased the corrosion stability in the ionic liquids studied. Hastelloy® C-276 showed the poorest corrosion resistance in all the ionic liquids tested. AISI 316L with high corrosion resistance and the lowest cost is recommended as the most attractive construction material for all the components, in an ionic liquid hydrogen compressor, which are in direct contact with ionic liquids used in this study.

Effect of molybdenum addition to ZA22 grain refined by titanium in the cast and after pressing by ECAP

Zinc aluminum alloys are versatile materials which are widely used in manufacturing many industrial and engineering parts due to their attractive properties. The ZA22 has the extra advantage of possessing super plastic behavior within the temperature range from 350 to 375°C. The equal channel angular pressing, ECAP is a relatively recent manufacturing process by which heavy plastic deformation can be produced in materials resulting in grain refinement of its microstructure. It is, therefore, anticipated that if the ECAP process is applied to the ZA22 alloy after being grain refined by certain grain refiners may produce super plastic behavior in this alloy at room temperature, by this eliminating the heating process and its costs, hence widening its applications rendering it to be cost effective. In this paper, the effect of molybdenum addition at a rate of 0.1 % wt. to ZA22 grain refined by Ti on its metallurgical and mechanical characteristics in the cast condition and after applying the ECAP process is investigated. It was found that addition of Mo to ZA22 either in the nonrefined or the refined by Ti resulted in refining its structure being more refined in the latter. The ECAP process resulted in further refinement of its structure of the ZA22-Ti, ZA22-Mo and the ZA22-Ti-Mo alloys. Regarding the mechanical behavior, it was found that addition of Mo to ZA22 resulted in pronounced reduction of its mechanical strength presented by the following values of the flow stress at 20% strain: from 451 MPa to 346 MPa, whereas pronounced increase in case of Ti addition i.e. by 22.22% and only increase of 1.1% when Mo is added in the presence of Ti. However the Vickers hardness HV was increased by 5% in case of Ti addition and 2.5% increase in case of Mo addition. Finally it was concluded that super plastic behavior was obtained at room temperature by the addition of Mo and the ECAP process.

Effects of heat treatments on the thermal diffusivity of Uranium-Molybdenum alloy

U-Mo alloys are the most investigated nuclear fuel material to be used in research reactors. The addition of molybdenum stabilizes the gamma phase of uranium and increases its melting point. A research program under development at Nuclear Technology Development Center (CDTN) aims the obtaining of uranium-molybdenum alloys to enable the high enriched uranium (HEU) to low enriched uranium (LEU) conversions. U-Mo ingots with 10% by weight were induction melted and heat treated at 300 °C for 72 h, 120 h and 240 h. Thermal diffusivity was determined by the laser flash method and thermal quadrupole method, from room temperature to 300 oC and 400oC. It was observed that the thermal diffusivity tends to increase with increasing temperature.

Microstructural Characterization and Properties of Microalloyed Powder Metallurgy Steels

The aim of this research is to investigate the effect of alloying elements of nickel, molybdenum, carbon and copper on hardness, density and microstructure of low alloy steel produced by powder metallurgy method. The results showed that molybdenum addition could lead to increase the density and hardness. Also, an increase in carbon content up to 1 wt. % could result in an increase in density and hardness. Copper is mainly added to increase strength as a result of solid solution hardening effect. Molybdenum is a ferrite stabilizer while Nickel is a strong austenite stabilizer. Consequently, the nickel and copper rich regions are mainly surrounded by austenite or bainite. Regions with higher amounts of alloying elements appeared to be martensitic islands. Increasing martensite and bainite volume fraction led to increase hardness.

Wear Resistance of H13 and a New Hot-Work Die Steel at High temperature

The friction and wear behaviors of a new hot-work die steel, SDCM-SS, were studied at high temperature under dry air conditions. The wear mechanism and microstructural characteristics of the SDCM-SS steel were also investigated. The results showed that the SDCM-SS steel had greater wear resistance compared with H13 steel; this was owed to its high oxidizability and temper stability. These features facilitate the generation, growth, and maintenance of a tribo-oxide layer at high temperature under relatively stable conditions. The high oxidizability and thermal stability of the SDCM-SS steel originate from its particular alloy design. No chromium is added to the steel; this ensures that the material has high oxidizability, and facilitates the generation of tribo-oxides during the sliding process. Molybdenum, tungsten, and vanadium additions promote the high temper resistance and stability of the steel. Many fine Mo2C and VC carbides precipitate during the tempering of SDCM-SS steel. During sliding, these carbides can delay the recovery process and postpone martensitic softening. The high temper stability postpones the transition from mild to severe wear and ensures that conditions of mild oxidative wear are maintained. Mild oxidative wear is the dominant wear mechanism for SDCM-SS steel between 400 and 700 °C.

Plastic deformation and corrosion in austenitic stainless steel: A novel approach through microtexture and infrared spectroscopy

The anodic potentiodynamic polarization behaviors of austenitic stainless steels, with varying Cu (copper) and/or Mo (molybdenum) additions, were explored after plane strain compression. Though all the alloys showed developments in deformed microstructures, the presence of Cu+Mo did not result in strain induced martensite formation (SIMF). However, the presence of Cu+Mo revealed the highest degradation in corrosion performance. A combination of microtexture measurements and fourier transform infrared spectroscopy (FTIR)-imaging revealed that the presence of SIMF promoted post-passivation stability or retention of a protective Cr2O3 film.

The effect of molybdenum on chromium deposition at (La0.8Sr0.2)0.95MnO3-δ cathode of solid oxide fuel cells

The effect of addition of molybdenum in FeCrMn based alloy on the chromium deposition and poisoning of LSM cathodes is investigated at 800 °C by electrochemical impedance spectroscopy and microstructure analysis. The FeCrMnMo ferrite stainless steel metallic interconnect shows much less Cr deposition and poisoning on the LSM cathodes as compared with the FeCrMn alloy. The addition of Mo into the alloy suppressed Cr evaporation from interconnects, decreased the degradation of cathode performance caused by Cr. According to SEM results, MoO3 and MnMoO4 is observed at the depositional area. The segregated MnO from LSM cathode can act as a nuclei agent, and react with vaporized Mo to form Mo-contained oxide particles, which will not inhibit the oxygen reduction reactions in the three phase boundary (TPB). As a result, suitable addition of Mo into the interconnect alloy can effectively alleviate the Cr poisoning of the LSM cathode.

Improved activity and stability of Ni-Ce0.8Sm0.2O1.9 anode for solid oxide fuel cells fed with methanol through addition of molybdenum

Ni-Mo-Ce0.8Sm0.2O1.9 (SDC) composites are prepared and investigated as anodes of solid oxide fuel cells with methanol as fuel. The addition of Mo improves the catalytic activity for methanol pyrolysis and the resistance to carbon deposition of Ni-SDC anode. The anode with a mole ratio of Mo to Ni of 0.03:1 exhibits the lowest polarization resistance. The cell with that anode and SDC-carbonate composite electrolyte shows a maximum power density of 680 mW cm−2 at 700 °C. The stability of the cell is enhanced with the increase of the content of Mo in the anode, which is mainly attributed to the decreased amount of carbon deposits with a high graphitization degree.

Promotional Effect of Molybdenum Additives on Catalytic Performance of CeO2/Al2O3 for Selective Catalytic Reduction of NOx

A series of CeO2/Al2O3 and CeMoxOy/Al2O3 catalysts were prepared by an extrusion method for selective catalytic reduction of NOx, and were characterized by techniques of XRD, XPS, N2-BET, H2-TPR and NH3-TPD. Promotional effects of molybdenum additives on catalytic performances and tolerances toward SO2 and H2O poisoning of the catalysts were comparatively studied. Results showed that the CeO2/Al2O3 catalyst with the Ce/Al molar ratio of 1:5 exhibited the best catalytic performance; molybdenum additives greatly improved catalytic performance of the CeMoxOy/Al2O3 catalysts, and the catalyst with the Al/Ce/Mo molar ratio of 5:1:0.15 calcinated at 550 °C exhibited the highest catalytic activity above 95 % in active temperature window of 250–430 °C under the gas hourly space velocity (GHSV) of 7200 h−1. Moreover, molybdenum additives broadened the range of the active temperature, and significantly enhanced the anti-sulfur poisoning ability. Analysis showed that the promotional effects of molybdenum additives were attributed to the improvement of specific surface area, increment of surface acidity and the enhancement of the redox properties. The molybdenum additives significantly increase the catalytic performance of CeO2/Al2O3 for selective catalytic reduction of NOx and greatly broaden the range of the active temperature. The reasons mainly due to molybdenum additives improve the specific surface area, increase the proportion of Ce3+/(Ce4++Ce3+) and Oα/(Oα + Oβ) on the surface, and enhance the amount of the Lewis acid sites.

Comparison between Mo Addition to Al Grain Refined by Ti and Ti+B on its Metallurgical and Mechanical Characteristics in the Cast and after ECAP Process Conditions

Aluminum and its alloys are widely used materials; they are next to steel in use mainly in the automobile industry due to their high strength – to – weight ratio and corrosion resistance beside its other attractive properties. Against their attractive properties; they have the disadvantage of solidifying in columnar structure which tends to reduce their mechanical characteristics and surface quality. Therefore it became customary to grain refine them either by Ti or Ti+B to overcome this discrepancy. In this paper, comparison between Molybdenum addition to commercially pure aluminum grain refined by Ti and Ti+B on its grain size and mechanical characteristics both in the cast and after pressing by the ECAP process is investigated and the obtained results are presented and discussed.

Characterization of weld metal microstructure in a Ni-30Cr alloy with additions of niobium and molybdenum

Additions of niobium (Nb) and molybdenum (Mo) were made to an Alloy 690 base alloy in order to investigate the formation of a eutectic constituent at the end of solidification and to evaluate the effect of the eutectic liquid on backfilling (or healing) of solidification cracks. Solidification cracking was induced using the cast pin tear test (CPTT) and regions of backfilling were located and characterized via optical and electron microscopy. Computational predictions of fraction eutectic and composition of the eutectic constituent were compared to experimental findings and were found to correlate well in both cases. The extent of crack backfilling increased significantly with increasing Nb content, but the addition of Mo did not seem to influence the amount of eutectic constituent or the degree of backfilling. SEM/EDS analysis confirmed that the eutectic composition is constant and that increasing Nb above 4wt% has little effect on expanding the solidification temperature range, but has a beneficial effect on mitigating solidification cracking by a crack healing effect.

Effect of Mo Content on the Corrosion Resistance of Fe-Based Amorphous Composite Coating

A Fe-based amorphous composite coating doped by molybdenum was fabricated by the pulse laser cladding technology. The substrate was a low carbon steel plate. The nominal composition of the powder in the range from 100 to 200 meshes was (wt.%) Cr:14.95, Mo:25.7, B:1.24, C:3.45, Y:3.40, Fe:51.29, which was selected for the laser cladding process. The microstructure, phase composition, hardness and corrosion resistance of the coatings were characterized by means of SEM, EDS, XRD , DSC and potentiodynamic polarization test. The results show that the coating which was composed of amorphous and nanocrystal phases had the dense structure and metallurgical bonding with the substrate, meanwhile with low porosity and cracks. The addition of molybdenum played an important role in improving the corrosion resistance of the coatings. With the increasing content of molybdenum, the hardness had no significant change, while the corrosion resistance of the coatings significantly increased. From the results of polarization curves, the corrosion current density of the coating added 0 wt.% Mo is higher than that of the coatings added 2 wt.% Mo and 10 wt.% Mo. The molybdenum has a superior effect on the corrosion resistance in Fe-based amorphous composite coating.

Effect of molybdenum addition on the precipitation of carbides in the austenite matrix of titanium micro-alloyed steels

The present work aims to reveal the effect of Mo on the precipitation behavior of MC-type (M = Ti and Mo) carbides in the austenite matrix of titanium micro-alloyed steel. The precipitation start-time–temperature curve was determined by a double-pass compression test on a Gleeble simulator, and the elemental mass fraction of MC-type carbides was measured by a physical–chemical phase analysis after a single-pass rolling test. The results shows that 0.2 wt% Mo accelerates the precipitation kinetics of MC-type carbides. During the initial stage of precipitation, Mo tends to distribute in the outer region of precipitates by replacing Ti despite of the high solubility of MoC in austenite. The replacement of Ti by Mo in TiC lattice leads to two opposite effects: First, it restrains MC precipitation due to the higher Gibbs free energy of (Ti, Mo)C relative to TiC; Second, it promotes MC precipitation by decreasing the interfacial chemical energy of MC/austenite system. The second effect is more pronounced during the initial stage of precipitation when MC precipitates are relatively small and hence MC precipitation is accelerated by Mo addition. Compared to TiC, (Ti, Mo)C with stronger coarsening resistance suppresses austenite recovery and recrystallization more effectively, which favors maintaining the deformation microstructures at high temperatures.