Mo Addition Research Articles

Influences of Ti and Mo alloying on the microstructure and properties of laser cladding for CoCrFeNi high-entropy alloys

The CoCrFeNiTi_(1-x) Mo_x high-entropy-alloy coating was prepared using a powder presetting method. The work investigated the influences of Ti and Mo addition on the microstructure and properties of CoCrFeNi high-entropy alloys. The first-principles calculation showed that CoCrFeNiTi_(1-x) Mo_x was mainly composed of the FCC phase, BCC phase, and IMCs. The coating exhibited high hardness, and the mechanical stability of the high-entropy alloys of FCC and BCC phases was maintained when x = 0.5. The coating primarily consisted of FCC, BCC, σand CoTi2 phases when x ≤ 0.75. The coating primarily consisted of FCC, BCC, σand Co2Mo3 phases when x = 1. It exhibited high microhardness, elastic modulus, elastic stiffness, and wear resistance when x = 0.5. Its average microhardness, local elastic modulus, and elastic stiffness were 873.28 HV0.5, 265.5606 GPa, and 102.8008 GPa, respectively. Besides, COF and the wear mass loss were 0.7026 mm3 and 0.0410 mm3, respectively. The coating exhibited exceptional corrosion resistance with a self-corrosion voltage of −0.700 V and a self-corrosion current of 5.387e-007 A when x = 1. The results offer practical guidance for preparing high-entropy-alloy coatings with various advantages as well as a theoretical foundation for preparing such alloys by laser cladding.

Effect of Mo addition on the microstructure and high-specific tensile strength of Fe–Mn–Al–Ni–C ferrous medium-entropy alloy

Molybdenum (Mo) is known to play various roles in ferrous materials, including promoting lattice distortion and forming different types of precipitates. In this study, Mo was added to the Fe–Mn–Al–Ni–C lightweight medium-entropy alloy system, and its effects on microstructure and tensile properties were investigated in comparison to the Mo-free counterpart. The addition of Mo retarded the kinetics of recrystallization and led to the precipitation of M6C-type carbides. In terms of tensile properties, the addition of Mo improved the strength of the alloy by enhancing solid solution strengthening and precipitation strengthening. In particular, the Mo-added alloy, annealed at 800 °C for 7.5 min, exhibited a yield strength of 1274 MPa and an ultimate tensile strength of 1550 MPa. This corresponds to a specific ultimate tensile strength of approximately 218 MPa g−1 cm3, along with a uniform elongation of ∼8.5 %. The Mo content in the solid solution and the presence of Mo-rich M6C-type carbides also contributed to high back stress hardening, which enhanced the alloy's ability for strain hardening and resulted in reasonable uniform elongation.

Effect of Mo addition on AC soft magnetic property, hardness and microstructure of FeCoNiMox (0 ≤ x ≤ 0.25) medium entropy alloys

The FeCoNi medium entropy alloy (MEA) has good alternating current (AC) magnetic properties but poor mechanical properties. This limits its application in soft magnetic materials. In this work, the effects of adding a small amount of Mo on the soft magnetic properties, hardness, and microstructure of FeCoNiMox (0 ≤ x ≤ 0.25) MEAs were investigated. The results indicate that a suitable addition of Mo can simultaneously improve the AC soft magnetic properties and hardness of the alloys. When x = 0.15, the total loss (Ps), AC coercivity (AC Hc), and maximum AC applied magnetic field (AC Hm) of the alloy were improved by 41%, 37%, and 38% over those of the x = 0 alloy, respectively. When x = 0.25, the nano-hardness of the alloy is 91% higher than that of the x = 0 alloy. The results of the microstructure analysis show that the appropriate addition of Mo homogenized the microstructure and refined the grains of the alloys. Meanwhile, the addition of Mo also led to the appearance of two FCC phases with alternating distribution and inhibited the formation of dislocation in the alloys. The mechanisms of adding elemental Mo to improve the soft magnetic properties and hardness of the alloys are discussed. Our work provides an effective way to enhance the soft magnetic and mechanical properties of MEA simultaneously.

Effect of Mo Addition and Water Vapor on the High-Temperature Corrosion Performance of APS Ni-Al-based Coatings

Effect of Mo Addition and Water Vapor on the High-Temperature Corrosion Performance of APS Ni-Al-based Coatings

The role of Mo on the creep deformation of a 4th generation Ni-based single crystal superalloy at 1100 °C

The effects of Mo content on the creep property of a 4th generation Ni-based single crystal superalloy were investigated systematically at high temperature and low stress. Under the condition of 1100 °C and 137 MPa, the performance of SC containing 2 wt% Mo and 3 wt% Mo was close, revealing that low Mo addition could meet the requirements of creep properties at 1100 °C and 137 MPa. However, the massive precipitation of TCP phases significantly degraded the creep performance when Mo content was more than 3 wt%. Mo addition also accelerated the broadening of the γ channel, decreasing the resistance of the dislocation slip. With regard to the positive impacts, Mo addition increased the magnitude of lattice misfit, leading to dense interfacial dislocation networks with high creep resistance. Mo also retarded the diffusion of alloying elements, thereby suppressing the formation of creep pores and the elemental inhomogeneity during creep. The comprehensive Mo-effect was summarized. Moreover, the optimum Mo content in the 4th generation single crystal superalloys was determined for the guidance of alloy design based on the creep results and comparison with other alloys.

Optimization of grain boundary by Mo nano-powder to enhance the coercivity of NdFeB magnets

The Mo doped NdFeB magnets were prepared by the dual alloy method. Through transmission electron microscopy (TEM) and electron probe microanalyzer (EPMA), it is observed that the Mo element is mostly distributed at the grain boundary, which isolates the main phase grains, thus improving the intrinsic coercivity (Hcj) of the magnets. When the addition of Mo nano-powder is increased from 0 to1.0 wt%, the Hcj of the magnet is significantly improved. Especially, when the addition of Mo nano-powder is 0.8 wt%, the Hcj of the magnet is 138 kA/m higher than that of the magnet without Mo addition. The current research work shows that the Mo doped magnet prepared by the dual alloy method effectively improves the Hcj of NdFeB magnets, which has practical application value and theoretical significance for the research and development of high-performance NdFeB magnets.

Preparation of self-supported Mo-doped hierarchical porous Ni–P toward highly efficient hydrogen evolution catalysis

In this contribution, the bulk self-supporting Ni–P catalysts with multistage pore structure were successfully optimized through the addition of Mo into precursors, in which Mo elements were mainly existed in the form of MoNi and MoNiP phases. After the adjustment of pore structure by Mo addition, the dealloyed CNMP-1 (2 at. % Mo) and CNMP-2 (8 at. % Mo) products were found to deliver the rather low overpotentials as 192 mV and 160 mV at current density of 10 mA cm−2, accompanied by Tafel slopes as 105.8 mV dec−1 and 98.2 mV dec−1 in 1 M KOH aqueous solution, respectively. In addition, CNMP-2 catalyst could exhibit a remarkably excellent stability after 100 h of continuous test with 2000 CV cycles. Based on the structural analysis, it was supposed that the excellent electrocatalytic performance of Ni–P skeleton catalysts might be attributed to the unique multistage pore structure, the synergetic effect between NixP and MoxNiyP, and the accelerated electron transport in the skeletons.

Vermiwash-mediated synthesis of molybdenum doped TiO2 nanoparticles: Evaluation of photocatalytic and biomedical properties

Combined effects of molybdenum (Mo) doping and enzyme incorporation on the photocatalytic and certain biomedical activities (antibacterial, antioxidant and antidiabetic) of titanium oxide nanopowder were studied. A soft-chemical eco-friendly approach was adopted to prepare enzyme powered Mo doped TiO2 nanoparticles (MTV). The photocatalytic dye degradation study against MB dye showed that the Mo addition increases the degradation efficiency from 73 to 86%. The enzyme incorporation into the system through the addition of vermiwash improves the efficiency further to 97%. The doping of Mo and addition of enzymes effectively controlled the growth of the tested bacteria Proteus vulgaris, Bacillus subtilis, and Pseudomonas aeruginosa. The minimum inhibitory concentration (MIC) of bare TiO2 against the bacteria viz. P. vulgaris, B. subtilis and P. aeruginosa are 125, 125 and 250 µg/mL, respectively, whereas the MIC of vermiwash activated Mo doped TiO2 are as low as 15.62 µg/mL, 07.81 µg/mL and 15.62 µg/mL, respectively. The antioxidant capacity of the sample MTV expressed potential free radical scavenging effect by 2,2-diphenyl-1-picrylhydrazyl (DPPH) with an inhibition of 89.77% and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with an inhibition of 87.02% compared to the standard ascorbic acid. In addition, the MTV nanopowders exhibited significant anti-diabetic effect (89.29%) by inhibiting the α-glucosidase enzyme. The mechanism involved in the enhancement of efficiency of the synthesized material is elaborated in this article. The XRD, SEM, FT-IR, Raman, XPS and BET results support the discussions on the property enhancement of the prepared material.

Effect of alloying (Cr, Mo, and V) on corrosion behaviors of API-grade steel in CO2-saturated aqueous solutions with different pH

The corrosion behaviors of steels alloyed with Cr, Mo, and V were examined in two different solution chemistries: near-neutral (pH 6) and weakly acidic (pH 4.5) solutions saturated with CO2. In near-neutral solutions, Cr alloying hindered the formation of a stable corrosion scale on the surface, reducing the corrosion resistance compared to conventional low-carbon steel. On the other hand, the alloyed steel exhibited higher corrosion resistance in acidic solutions. In contrast to the conventional carbon steel, which had a single scale of crystalline FeCO3 scale on its surface, a more stable bi-layer of corrosion scale consisting of an inner layer of amorphous Cr(OH)3 and an outer layer of crystalline FeCO3 was developed on the alloyed steel. This was attributed primarily to the increased thermodynamic stability of Cr(OH)3 with an increase in Cr contents at this solution pH. Moreover, the increase in Cr with Mo addition resulted in a refinement of FeCO3 on the outer surface through increased hydrolysis reactions leading to a decrease in the local pH on the steel surface. Furthermore, adding V, even in minute quantities contributed to an increase in Cr-enrichment in the inner scale by suppressing M7C3 precipitation and leaving more Cr in the solid solution.

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.

Effect of Mo addition on the mechanical and tribological properties of magnetron sputtered TiN films

Ternary-based titanium nitride (TiN) thin films have drawn attention toward rational applications due to their wear resistance, high hardness, and corrosion resistance. The influence of Mo content on the structural, tribological, and mechanical properties of TiN films is reported in this study. The microstructure and elemental composition of the as-deposited TiMoN films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), nanoindentation, and ball-on-disc wear tests. XRD results showed that the as-sputtered TiMoN films consisted of a formation of solid solution of TiN and MoN mixture phases. With 18 at. % of Mo, the mechanical property of TiMoN films was enhanced, and the film exhibited a high hardness of 28 GPa. Moreover, this addition led to a wear rate of 0.40 and 6.34 × 10−6 mm3/Nm and to lower the friction coefficient to values lower than the corresponding binary TiN film. This was attributed to the multi-phase strengthening and higher (H/E, H3/E2) values, which indicate that the mechanical properties and the wear resistance of TiN can be enhanced by alloying with Mo.

Effects of Mo and Controlled Cooling on Microstructure and Properties of Thick‐Wall High‐Strength Pipeline Steel

Herein, the effect of molybdenum (Mo) and postrolling cooling processes on the mechanical properties and microstructure transformation characteristics of an X80 thick‐wall high‐strength pipeline steel are deeply investigated. The results reveal that the yield strength and tensile strength of the steel are enhanced with Mo addition at the equalization temperature of 480 °C at a cooling rate of 25 °C s−1, accompanied by the improvement in the yield ratio. However, when the postrolling cooling temperature is reduced to 380 °C, the mechanical properties of steels with Mo‐free and 0.29 wt% Mo are comparable. The mechanistic study indicates that the Mo addition would inhibit the transformation from deformed austenite to polygonal ferrite, and promote the transformation of acicular ferrite/granular bainite at medium–low temperatures, as well as significant differences in the volume fraction, size, and morphology of martensite/austenite (M/A) in the matrix. Notably, the volume fraction of M/A decreases from 7.2% to less than 1.0% with Mo content increasing, while its average size also reduces from 1.5 to less than 1.0 μm. And the fine, spheroidal, and dispersed M/A is found to play a vital role in the high‐strength and excellent low‐temperature toughness of the steel.

Effects of Mo Particles Addition on the Microstructure and Properties of 316 L Stainless Steels Fabricated by Laser Powder Bed Fusion.

Application of the 316 L stainless steel (SS) is limited by its relatively low wear resistance, insufficient strength, and poor corrosion resistance in special environments. To this end, effects of Mo particles addition on the microstructure, mechanical properties, and corrosion resistance of the laser powder bed fusion (LPBF) 316 L SS are investigated in this study. The results show that the addition of Mo particles from 0 wt.% to 10 wt.% can modify the crystal orientation and improve the strength, wear resistance, and corrosion resistance of LPBF 316 L SSs. Particularly, the LPBF 316 L SS forms a biphasic structure with a similar ratio of α-Fe to γ-Fe with 5 wt.% Mo addition. As a result, the corresponding samples possess both the excellent toughness of austenitic SSs and the high strength and corrosion resistance of ferrite SSs, which reaches a high tensile strength of about 830 MPa, together with a low friction coefficient of 0.421 μ. Since the Mo particles addition is beneficial to increase the content of Cr2O3 on the samples surface from 13.48% to 22.68%, the corrosion current density of 316 L SS decreases by two orders of magnitude from 569 nA to 6 nA, while the mechanical properties remain favorable. This study is expected to serve as a reference for the preparation of LPBF SSs with excellent integrated performance.

Observed reduction in fracture toughness of AlN and AlN–Mo ceramic matrix composites with carbon additive

The fracture toughness of AlN ceramic matrix composites containing carbon (0.5 vol%), yttria (5.0 vol%), and Mo (0.0–4.0 vol%) was evaluated using Vickers indentation. The results of these measurements were compared to a carbon-free, commercial AlN (ST-200 ALN) as well as to AlN and AlN–Mo compositions from the literature. The presence of added carbon was found to correlate with a 21% reduction in fracture toughness of the 0.0 vol% Mo carbon-containing sample, compared to commercial ST-200 AlN, in both the A-orientation (indentation parallel to the pressing direction) and the B-orientation (indentation perpendicular to the pressing direction). Mo additions at small loading fractions (~ 0.25 vol%) were found to exhibit greater-than-expected increases in fracture toughness in the A-orientation, when compared to literature data on AlN–Mo composites. This increase in fracture toughness correlates to the removal of elemental carbon in the AlN matrix through reaction with the Mo additive, forming Mo2C, localized at the Mo particle sites. Further increasing Mo loading was observed to result in generally increasing fracture toughness values, as would be expected from literature data.Graphical abstract

Effect of Mo Addition on the Performance of Ni-Based Methanation Catalysts Supported by Halloysites

Effect of Mo Addition on the Performance of Ni-Based Methanation Catalysts Supported by Halloysites

High-temperature oxidation resistance of ternary and quaternary Cr-(Mo)-Si-B2-z coatings — Influence of Mo addition

The Si-based alloying of transition metal diborides is a promising strategy to improve their limited oxidation resistance in high-temperature environments. In this study, we investigate the oxidation resistance of ternary and quaternary Cr-(Mo)-Si-B2-z coatings sputter-deposited from alloyed CrB2/TMSi2 targets (TM = Cr or Mo). The as-deposited Cr-(Mo)-Si-B2-z coatings are stabilized in the single-phased hexagonal AlB2-structure, except the high-Si containing Cr0.26Mo0.11Si0.24B0.39 presenting amorphous character. The Mo-containing Cr-Mo-Si-B2-z films exhibit relatively high hardness compared to their ternary Cr-Si-B2-z counterparts, obtaining up to 26 GPa due to the formation of (Cr,Mo)B2 solid solutions. The Si-alloying in ternary and quaternary coatings provides oxidation resistance up to 1200 °C, owing to the formation of highly protective double-layered scales consisting of SiO2 with a Cr2O3 layer on top, inhibiting oxygen inward diffusion. The quaternary Cr0.31Mo0.07Si0.15B0.47 coating is distinguished by superior oxidation resistance with lower porosity and void formation compared to the ternary Cr0.37Si0.16B0.47. Mo proved to be the key element for the higher stability and enhanced oxidation resistance due to the evolution of the MoSi2 phase at ~600 °C. This phase formation controls the Si diffusion and mobility within the microstructure, thus reducing the porosity and governing the Si supply to form SiO2 scale. The quaternary Cr0.31Mo0.07Si0.15B0.47 coating maintained an oxidation resistance up to 30 h at 1200 °C by forming a 2.5 μm dense amorphous Si-based oxide scale with a thin Cr2O3 on top.

CaMoO4-enhanced Ni-CaO bifunctional catalyst for biomass pyrolysis to produce hydrogen-rich gas

The development and utilization of bifunctional catalysts facilitated hydrogen-rich gas production from biomass pyrolysis to achieve high-value biomass conversion. The effects of different secondary metals (Fe, Mo, Ce) doping and Mo addition ratios on the performance of biomass catalytic pyrolysis for hydrogen production were investigated. The results showed that the Mo0.5Ni1Ca7 catalyst had the best catalytic activity, where the H2 percentage was 69.59 vol%, and the yield reached 617.57 mLgbiomass−1. The CO2 concentration of the Mo0.5Ni1Ca7 catalyst was reduced by 10.6% compared to the Ni1Ca7 catalyst, which enhanced the adsorption performance of the catalyst. The intense interaction between Mo and Ca formed CaMoO4, which inhibited the formation of CaCO3 and promoted the dispersion of the active phase. The Mo0.5Ni1Ca7 catalyst had the largest NiO/Ni (OH)2 ratio and Mo6+/Mo5+ ratio, further enhancing the catalyst's stability and catalytic activity. Considering the effect of pyrolysis temperature on H2 concentration and yield, it was found that 600 °C was a relatively suitable catalytic pyrolysis temperature. This paper explored using Mo-modified catalysts in biomass catalytic pyrolysis for the first time, providing new ideas for developing bifunctional adsorption catalysts. Eventually, it provided a new way for biomass pyrolysis for hydrogen production technology.

Electrical resistivity and flexural strength of mullite‐bonded porous SiC: Effect of transition metal additives

AbstractThe influence of various transition metal (Mo, Co, Ni, and Fe) additives on the electrical and mechanical properties of mullite‐strengthened SiC sintered in the range of 1100–1500°C under an Ar atmosphere was investigated. Kaolin was added as a low‐temperature sintering aid in the designed formulations. The addition of metal additives reduced the electrical resistivity, enhanced the mechanical strength, and produced samples with an approximately 40% porosity. The decrease in electrical resistivity was attributed to the in situ formation of electrically conductive metal silicides, whereas the conversion of kaolin to mullite enhanced the mechanical properties. The comparative study shows that at the same metal‐additive content (15 wt%), Fe was the most effective element to reduce the electrical resistivity and increase the flexural strength, which were recorded as 8.0 × 100 Ω cm and 20 ± 2 MPa, respectively, of the samples sintered at merely 1300°C.

Investigating the influences of Fe, Mn and Mo additions on the evolution of microstructure and mechanical performances of Al–Si–Mg cast alloys

Understanding the evolution of Fe–containing intermetallic compounds (Fe–IMCs) in Al–Si–Mg alloys is essential for improving the mechanical performances. This paper aims to systemically evaluate the influences of both the single addition of Mn or Mo, and the combined additions of Mn and Mo on the evolution of Fe–IMCs and mechanical performances of Al–Si–Mg cast alloys. Results reveal that the as–cast microstructures of these alloys are primarily composed of Al3M (M means Ti, Zr, or TiZr), α–Al, eutectic Si, Mg2Si, Q–Al5Cu2Mg8Si6, and some irregular Fe–IMCs. It is clear that the morphology and size of Fe–IMCs are significantly affected by the single or combined addition of Mn and Mo. Moderate Mn content facilitates the formation of Chinese script–like α–Al(FeMn)Si phases that are favorable to the mechanical properties. The combined addition of Mn and Mo refines the α–Al(FeMn)Si phases and promotes the formation of Chinese script–like α–Al(FeMnMo)Si phases. Furthermore, as the Mo level increases, β–AlFeSi, π–Al8FeMg3Si6, and α–Al(FeMn)Si disappear successively, which also helps improve the mechanical performances. In this article, maximum hardness, ultimate tensile strength, yield strength and elongation of 87.04 HV, 275.34 MPa, 139.70 MPa, 7.88% are obtained when Fe, Mn and Mo are added at 0.20wt.%, 0.02wt.%, and 0.27wt.%, respectively. The purpose of this work is to provide an efficient method to minimize or even eliminate the adverse effects of Fe–IMCs and thus improve the mechanical performances of Al–Si–Mg cast alloys.

Effect of Mo on high entropy Ti-Nb-Zr-Ta alloy: Phase equilibria, microstructure and mechanical properties

Thermal and mechanical properties of Ti-Nb-Ta-Zr high entropy alloys are often influenced by element content and manufacturing routes, producing significant differences between mechanical properties and microstructure. This work presents a Ti-Nb-Ta-Zr alloy in which Mo is added by adjusting the composition with phase equilibria simulation, improving the mechanical properties based on a mixture of two chemically different solid solutions (BCC1 and BCC2). The materials were produced by arc-melting suction casting. Characterization of the dendritic and interdendritic zones was carried out by means of X-ray spectroscopy, indicating the segregation of Ta and Nb in BCC1 and Zr and Ti in BCC2 phases. The dislocation density increased preferentially in the interdendritic Zr-Ti rich zones. The mechanical properties results were related to the chemical differences between the BCC1 and BCC2 lattice parameters induced by the Mo addition. With Mo segregating between both BCC cells, the resulting microstructure increased the yield strength, being confirmed with the kernel average maps, which showed that, after compression tests, the interdendritic zone accumulated a high density of dislocations, resulting in the segregation of Ti and Zr, affecting the mechanical response of Mo containing alloy.