Effect Of Molybdenum Addition Research Articles

Effect of molybdenum addition on oxidation behavior and secondary protection mechanism of FeCrAl coatings

FeCrAl alloy coatings are widely used for their excellent oxidation resistance at high temperatures, but they can suffer from rapid material degradation due to breakaway oxidation of the coating. Composition manipulation is an essential way to prompt the oxidation resistance of the coatings. In this study, we prepared Fe-13Cr-7Al (at.%) alloy coatings with varying Mo contents (Mo = 0, 1.5, 3, 6 at.%) by magnetron sputtering and investigated their oxidation behaviors at 550 °C. The surface and cross-sectional morphologies of the coatings before and after oxidation were examined using electron microscopy. The results showed that the crystalline grain and particle size of the coatings decreased significantly with the increase of Mo content, leading to a notable increase of grain boundaries and further enhancing element diffusion during the oxidation tests. As a result, a protective and stable oxide scale rapidly grew on the surface of FeCrAlMo coatings during oxidation. Moreover, FeCrAlMo coatings demonstrated improved secondary protection mechanisms with increasing Mo contents. This was attributed to the formation of an internal oxidation layer of a spinel barrier (M3O4, M = Fe, Cr, Al, Mo) beneath the outer oxidation layer. The spinel barrier impeded inward diffusion of oxygen ions and outward diffusion of metal cations, resulting in enhanced oxidation resistance of the spinel-type oxide. The thermodynamic calculations were used to evaluate the oxidation mechanisms of the coatings. These results provide a deeper understanding of the effect of Mo addition on the oxidation behavior and underlying protection mechanisms of FeCrAl coatings, and can be beneficial for designing and developing materials for use in oxidation environments.

Further investigations into alloy induced acidic fluxing

ABSTRACT Gas turbine materials often feature precipitates containing refractory metals to enhance their mechanical strength. This can make them susceptible to alloy-induced acidic fluxing whereby refractory elements increase the acidity of salt deposits. It is not clear to what degree degradation around alloy precipitates is caused by alloy-induced hot corrosion mechanisms, or the inability to develop a protective scale where precipitates are located. The effect of alloy-induced hot corrosion was isolated from the disruption of the protective-scale formation by adding particles of molybdenum to the 80/20 (Na/K)2SO4 deposit for a ‘deposit re-coat’ style hot corrosion test. The resulting morphologies were compared to samples exposed without the addition of molybdenum. Morphology changes were investigated using scanning electron microscopy with energy-dispersive X-ray mapping. Results show a mix of sulphidation and pitting. The effects of molybdenum additions appear more severe for MarM 509 compared to PWA 1483.

The role of molybdenum on evolution of deformation texture in the cold rolled Fe30Mn5Al1C-xMo lightweight austenitic steels

The effect of molybdenum addition on the evolution of deformation texture during cold rolling is studied in Fe30Mn5Al1C-xMo (x = 0−3 wt%) light weight austenitic steels using EBSD. All the alloys have random texture prior to cold-rolling. After cold rolling, molybdenum promoted the formation of Brass-type texture. This texture can be attributed to dislocation based active deformation mechanisms because no deformation twins were found in the microstructure. The intensity of the major texture components: Brass and S increased up to 2 wt% Mo and then decreased. The increase in the molybdenum content did not affect mechanical properties significantly.

Effect of molybdenum addition on microstructure and mechanical properties of 90% tungsten heavy alloys

Powder metallurgy approach was used to produce fine-grain tungsten heavy alloys (WHAs), and the effect of Mo addition on the microstructures and mechanical properties of the alloy was discussed. The W-Mo-Ni-Fe ultrafine composite powders were prepared via method consisting of steps of carbothermic pre-reduction and subsequent deep hydrogen reduction. The sintered compacts of these W-Mo-Ni-Fe composite powders reached virtually full densification after sintering at 1500 °C for 2 h. It was discovered that the W grain size of WHAs reduced due to the Mo addition (0, 2.5, 5, 10 wt%). Tensile test results showed that the alloy with 5 wt% Mo exhibited the maximum ultimate tensile strength and elongation, which has a significant relationship with finer W grain size, lower WW contiguity and higher volume fraction of the γ-(Ni, Fe) matrix phase. It was also concluded that the major fracture characteristic of WHAs were transformed from WW decohesion to W-matrix interface separation with increasing the addition amount of Mo.

Effect of Molybdenum Addition on Microstructure and Mechanical Properties of 90 % Tungsten Heavy Alloys

Effect of Molybdenum Addition on Microstructure and Mechanical Properties of 90 % Tungsten Heavy Alloys

Effect of Molybdenum (Mo) Addition on Phase Composition, Microstructure, and Mechanical Properties of Pre-Alloyed Ti6Al4V Using Spark Plasma Sintering Technique.

The effect of molybdenum additions on the phases, microstructures, and mechanical properties of pre-alloyed Ti6Al4V was studied through the spark plasma sintering technique. Ti6Al4V-xMo (where x = 0, 2, 4, 6 wt.% of Mo) alloys were developed, and the sintered compacts were characterized in terms of their phase composition, microstructure, and mechanical properties. The results show that the equiaxed primary alpha and Widmänstatten (alpha + beta) microstructure in pre-alloyed Ti6Al4V is transformed into a duplex and globular model with the increasing content of Mo from 0 to 6%. The changing pattern of the microstructure of the sample strongly influences the properties of the material. The solid solution hardening element such as Mo enhances mechanical properties such as yield strength, ultimate tensile strength, ductility, and hardness compared with the pre-alloyed Ti6Al4V alloy.

Effect of Molybdenum Addition on Microstructural and Mechanical Characterization of Highly Porous Steels

In this work, the influences of adding different amounts of molybdenum (0, 0.5, 1, 2, and 4 wt%) on the microstructure and mechanical properties of highly porous steels fabricated using powder metallurgical water-leachable space holder technique were studied. The microstructure of cell walls and morphologies of cells and micro-pores were evaluated using an optical microscope and scanning electron microscope equipped with X-ray energy dispersive spectroscopy. To evaluate the mechanical properties, compression tests were conducted on the highly porous steel specimens. The results demonstrated that about 90 wt% of urea granules are discontinuously removed during the multi-stage leaching process. The relative density of the highly porous steels was measured between the range of 0.18 and 0.22 and it increased by adding the molybdenum content. Ferrite, fine pearlite, and distributed molybdenum islands formed the microstructure of cell walls. The stress–strain curves contained linear elastic region, long saw-toothed plateau region, and fracture point. By changing the amounts of molybdenum from 0 to 4 wt%, mean modulus of elasticity, plateau stress, and density of energy absorption showed 0.75, 7.32, and 6.75 times improvement, respectively. Also, yield strength and failure strain revealed up–down behavior.

Effect of Mo addition on the microstructural evolution and γ-U stability in Th-U alloys

Previous studies have established that Th-U alloys up to 20 wt%U have good irradiation stability. To retain or enhance the irradiation stability of Th-U alloys with increase in uranium content, uranium should be stabilised as isotropic γ-U. Molybdenum is one of the most potent stabilizers of γ-U. Although U-Mo system is well studied, scant availability of open literature related to Th-U-Mo system indicates, need for planned studies. In the present study, effect of molybdenum addition on the microstructural evolution and stability of γ-U phase in some selected compositions of Th-30U alloy has been investigated. A pseudo binary phase diagram of Th-Mo at 30 wt%U has been constructed by CALPHAD approach using respective binary interaction parameters. The origin of as cast microstructure is explained with the help of assessed phase diagram. Three different compositions of Th-U-Mo alloy with varying molybdenum content have been evaluated for their potential application as nuclear fuel.

The Effects of Molybdenum Additions on the Sintering and Mechanical Behavior of Ultrafine-Grained Tungsten

Tungsten (W) is a brittle material at room temperature. Although the lack of ductility remains a difficult challenge, solid solution alloying of tungsten with rhenium offers an effective approach to improve tungsten’s room temperature brittleness. There are strong motivations to seek a substitute element for rhenium, because it is prohibitively expensive, for manufacturing solid solution tungsten alloys with improved mechanical behavior. As one of the potential substitute elements, the effects of molybdenum were studied in terms of its effects on densification and the grain growth of samples produced with nano-tungsten powder by pressureless sintering. A study on the mechanical properties of sintered tungsten-molybdenum alloy, including hardness, indentation toughness and bending stress–strain relationships, is also reported. It was found that alloying tungsten with molybdenum clearly reduced tungsten grain size, significantly increased hardness and indentation toughness, and also resulted in an appreciable improvement in tungsten’s tensile behavior during bending.

Effect of molybdenum addition in nickel-based catalyst on hydrogenation reaction of 2-ethyl-2-hexenal hydrogenation to 2-ethyl-hexanol

The 2-ethyl-hexanol compound is much needed in the plasticizer industry as a precursor for the synthesis of bis diesters (2-ethyl hexyl) phthalate (DEHP). This compound can be synthesized by oxo reaction. One of the steps in the oxo reaction is consecutive hydrogenation reaction of the 2-ethyl-2-hexenal to 2-ethyl-hexanol. This reaction requires nickel-based catalyst as an effective step for obtaining higher and purer 2-ethyl-hexanol yields. This research aims to develop the formula and procedure of catalyst synthesized in Laboratory of Catalysis and Reaction Engineering Institut Teknologi Bandung and get a rate of the reaction. The catalysts were synthesized by co-impregnation with a nickel content of 20%-w and varied with molybdenum loading (5-20%). The support that used for these metals is alumina-phosphate (AlP2). The synthesized catalysts were tested for their activity against the 2-ethyl-2-hexenal conversion at 120°C, 30 bar in the fixed bed reactor and compared its performance with a commercial catalyst. The results showed the addition of molybdenum loading increases selectivity of 2-ethyl-hexanol but decrease the conversion of 2-ethyl-2-hexenal. The highest selectivity was achieved by Ni5-Mo20/AlP2 (X=31%, S=85%), but the highest conversion was achieved by Ni20/AlP2 (X=88%, S=32%). Nickel tend to play a part of breaking the C=C bond. Meanwhile, molybdenum tends to break the C=O bond. This shows that the hydrogenation of C = C bonds and the C = O bond is very depending on nickel and molybdenum metal loading.

Effect of molybdenum additions on the microstructures and corrosion behaviours of 316L stainless steel-based alloys

ABSTRACTAlloys were made by alloying 5, 10, 15, 17.5 and 20 wt-% Mo with Type 316L stainless steel. Sigma phases containing 21–29 wt-% Mo formed along the austenite grain boundaries with the addition of 5 wt-% Mo and increased with additions up to 15 wt-% Mo, but they decreased with further additions. Laves phases containing 33–40 wt-% Mo co-precipitated at additions of 10 wt-% Mo which increased with further Mo increases. The corrosion resistance, assessed by potentiodynamic polarisation in a 10 mM NaCl solution adjusted to pH 4, increased relative to Type 316L for alloys made with 5 and 10 wt-% added Mo, but decreased with further additions due to preferential corrosion of the Laves phase. The alloy made with 10 wt-% added Mo had the highest corrosion resistance due primarily to the high Mo content of the austenite.

Microstructures and mechanical properties of as‐cast titanium–zirconium–molybdenum ternary alloys

AbstractIn this study titanium–zirconium–molybdenum alloys (Ti50Zr50)100‐xMox (xMo; x = 0 at.%, 1 at.%, 3 at.%, 5 at.% or 7 at.%) were investigated, focusing on the effect of molybdenum addition on their microstructures and mechanical properties. Transmission electron microscopy observations revealed that the binary Ti50Zr50 alloy was composed entirely of an acicular hexagonal structure of the α’ phase. When the molybdenum content was 1 at.%, the alloy was composed of β and ω phases. However, when 3 at.% or more molybdenum was added, only the equiaxed, retained β phase was observed. Tensile tests at room temperature indicated that the mechanical properties of the 1Mo alloy were inferior owing to the embrittlement effects of the ω phase and the difficulty of dislocation motion through the ω phase. Our research suggested that the 5Mo alloy had excellent ductility (16.5 %) as well as adequate strength (780 MPa). The improved mechanical properties were attributed to the enhanced stability of the β phase and the disappearance of the ω phase.

Effect of molybdenum addition on hardenability of chromium-boron steels used for press hardening applications

Two laboratory heats of low-Carbon low-alloy steels, one with boron and chromium additions and other with boron, chromium and molybdenum additions were made and cast into pencil ingots. These ingots were hot-rolled to 2 mm sheets suitable for press hardening application in an experimental rolling mill. A detailed study was made on the effect of various alloying elements on the microstructure and mechanical properties of these steels. A significantly higher hardness (~496 VHN), yield strength (~1137 MPa) and ultimate tensile strength (~1673 MPa) with comparable elongation (~6%) could be achieved in the as rolled and water-quenched Mo-Cr-B steel in comparison to Cr-B steel under similar processing condition. Moreover, a reduction of critical cooling rate by10?C/s was observed in this steel to obtain fully martensitic structure. The combined addition of boron, chromium and molybdenum was found to be more effective than that of boron and chromium in enhancing the microstructure and mechanical properties of boron-added steels. Additionally, a few hot compression tests were carried out to simulate the press hardening process of these experimental steels. It was found that one of the press hardening process parameters, viz., prior strain had a greater impact on the transformation behaviour of Cr-B and Mo-Cr-B steels during cooling.

Effect of molybdenum addition on the microstructure and mechanical properties of Cr3C2-20 wt. % Ni cermet

Effect of Mo addition on the microstructure and mechanical properties of Cr3C2-20 wt. % Ni cermet was investigated. Three different phases can be seen in the microstructure after adding appropriate molybdenum. The completely undissolved (Cr, Mo)3C2 phase maintains the original grain size and effectively prevents the (Cr, Mo)7C3 grains from merging and growing. The relative densities of the sintered specimens decrease slightly, while the hardness and bending strength increase firstly and then decrease slightly with the increase of Mo content. The maximum values of the hardness (88·6 HRA) and bending strength (1200 MPa) are achieved with 1 wt. % Mo addition.

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

Abstract

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.

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.

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.

Effect of Molybdenum Additions on the Microstructure and Properties of WC–W2C Alloys

The paper examines how additions of 5, 10, and 20 wt.% molybdenum influence the structure, stress–strain state, phase composition, and size of phase components in WC–W2C alloys. It is found that 5 wt.% molybdenum leads to 30% increase in the microhardness and twofold to threefold increase in the wear resistance of cast tungsten carbide compared to the alloy without additions. Higher molybdenum content of the WC–W2C alloys changes the phase composition and increases compressive stresses in the W2C matrix phase and tensile stresses in WC, (Mo, W)2C, and Mo2C inclusions.

Effect of molybdenum addition on aluminium grain refined by titanium on its metallurgical and mechanical characteristics in the as cast condition and after pressing by the equal angular channel process

Aluminium and its alloys are versatile materials which are widely used in industrial and engineering applications due to their attractive characteristics. However, they solidify in columnar structure which tends to reduce their surface quality and mechanical strength. It is therefore, grain refined by grain refiners i.e. titanium or titanium+boron. The equal angular channel pressing, ECAP, process is a recent method for producing severe plastic deformation in materials. In this research work, the effect of addition of molybdenum either alone or in the presence of titanium to commercially pure aluminium on microstructure and mechanical behaviour is investigated in two conditions; first, in the as cast condition, and second after pressing by the ECAP process at room temperature. It was found that addition of Ti alone at a rate of 0.15% weight to commercially pure Al resulted in grain refining of microstructure and a grain size of 91μm was obtained. However, after pressing by the ECAP process further refinement was achieved and the grain size was reduced to 18μm. Addition of Mo alone to aluminium at a rate of 0.1% resulted in grain size of 76μm in the as cast condition and 32μm after pressing by the ECAP process. The combination of the two elements Ti and Mo together resulted in 48μm grain size in the as cast condition, compared to 40μm after pressing by the ECAP process. Furthermore, it was found that in the as cast condition: addition of Ti alone to Al resulted in enhancement of its mechanical behaviour by an increase of 5.2% increase in its flow stress at 20% true strain, whereas addition of Mo either alone or in the presence of Ti resulted in decrease of its flow stress at 20% by 9% and 5.6% respectively. However, after pressing by ECAP: it was found that addition of Ti or Mo either alone or together to Al resulted in increase of its flow stress at 20 % strain by the following percentages 5.49, 4.74 and 10.3% respectively.