Effect Of Mo Content Research Articles

Microstructure evolution, mechanical properties, and corrosion behavior of in-situ TiC/TC4 composites through Mo addition

To further improve the mechanical properties and corrosion resistance of the composites, in-situ TiC/TC4-xMo composites were fabricated. The effect of Mo content on the microstructure evolution, mechanical properties, and corrosion behavior of the composites was investigated. The results show that with the increase of Mo content, the amount of β-Ti phase and the size of the TiC particle increase. The mechanical properties and corrosion resistance of the composites can be significantly enhanced through Mo addition. The TiC/TC4 composites containing 10 wt% Mo exhibits superior mechanical properties and corrosion resistance. Grain refinement, load transfer, and solid solution strengthening are the main strengthening mechanisms for improving the strength of composites. In addition, the increase of the β-Ti content, the presence of TiC, and the solid solution of Mo elements contribute to enhancing the corrosion resistance of the composites.

Influence of different metal-modified Beta zeolites on the liquid-phase isomerisation of xylene and reaction mechanisms

PX is a very important chemical raw material. There are few studies on the liquid-phase isomerisation of xylene. Here, a series of Beta catalysts with different metal modifications were prepared and tested for many characterisations. The reaction performance of the catalysts was evaluated in the liquid-phase MX isomerisation reaction. The results show that the loading of La, Ce, Mo,Fe and Mg metals decreases the specific surface area and acid content of Beta zeolite. Among them, Mo has a strong interaction with the skeleton Al atoms in Beta. The side reactions of MX isomerisation were inhibited by metal loading, and the selectivity of PX and OX was improved. The effect of Mo content on the liquid-phase isomerisation of MX was further investigated. The selectivity of PX can be improved by appropriate Mo content. This is related to the reaction mechanism of the liquid-phase isomerisation of MX at mainly low temperatures. The acidic site density of B and L acids on the catalyst surface was successfully modulated by Mo loading. At 260 °C, the conversion of MX over Mo/Beta catalyst was about 33 % and the PX yield was 12.83 %. In addition, based on the results of liquid-phase isomerisation of MX, OX and PX, the transformation relationship between the three isomers was investigated.

Effect of Mo Content on the Structural, Mechanical, and Tribological Properties of New Zr-Nb-Mo Alloys Obtained by Combining Powder Metallurgy and Vacuum Arc Melting Methods.

Considering the high demand for innovative solutions in medicine, a major increase in interest in biomaterials research has been noticed, with the most significant advancements in metals and their alloys. Titanium-based alloys are one of the most recognised in the scientific community but do not represent the only way to achieve optimal results. Zirconium alloys for medical applications are a novelty with significant research potential based on their outstanding properties, which may be of value for medicine. The aim of the present study was to obtain new biomedical Zr-Nb-Mo alloys with varying ratios of their respective elements-Zr and Mo-using combined powder metallurgy (PM) and arc melting (VAM) methods. The obtained samples underwent microstructure analysis using an optical microscope (OM) and a scanning electron microscope (SEM). The study of element distribution was conducted with energy dispersive spectroscopy (EDS), whereas the phase composition was determined using X-ray diffraction (XRD). Mechanical properties were examined with a Micro Combi Tester MCT3, whereas tribological properties were assessed with a TRN Tribometer, and Ringer's solution was used as a lubricant. Additionally, the wear tracks of the studied samples were observed using the SEM. The research results indicated that increased Mo content conduced to microstructure refinement and homogeneity. Furthermore, the higher content of this element contributed to the growth of the HVIT, HIT, and EIT parameters, together with the improvement in the tribological performance of the alloys. XRD analysis revealed that the obtained samples were multiphase, and raising the Mo addition promoted the formation of new phases, including a ternary phase-Zr0.9Nb0.66Mo1.44 (Fd3¯m). The chemical composition study showed uneven distribution of niobium and areas of uneven mutual distribution of zirconium and molybdenum.

Effect of Mo content on microstructure and mechanical properties of CoCrFeNi Series high-entropy alloys

In this paper, the microstructure and mechanical properties of CoCrFeNiMox (x = 0, 0.1, 0.3, 0.5, 0.7, and 1.0) high-entropy alloys (HEAs) prepared with high-vacuum arc melting method were studied in detail. After Mo-doping, the strengthening mechanism of HEAs mainly included the component segregation strengthening and the second phase strengthening. Cr and Mo elements were enriched at the grain boundary of HEAs, which leaded to the formation of σ phase and strengthens the alloys. The microhardness and strength increased with Mo contents, while the elongation decreased gradually. Among which, the higher microhardness, yield strength, and ultimate tensile strength of CoCrFeNiMo0.3 alloy reach 205.96 HV, 292.22 MPa, and 593.25 MPa, respectively, in compared with other alloys. More importantly, the percentage elongation of which remains 37.36%, and the microhardness distribution was uniform with an average value of 7.4 GPa and an elastic modulus of 263.6 GPa. The research findings presented in this paper could serve as a valuable theoretical basis and practical foundations for the strengthening efforts of face centered cubic (FCC) HEAs.

Effect of mo content on the microstructure and properties of powder metallurgy iron based friction materials

This article uses powder pressing and sintering methods to prepare iron-based friction materials. The influence of molybdenum on the microstructure and comprehensive properties of powder metallurgy friction materials was studied from the aspects of density, hardness, and wear resistance. The results show that with the increase of Mo mass fraction, the sintering density of iron-based friction materials gradually increases, and the hardness of sintered materials first shows an increasing trend. As the Mo content increases by more than 12%, the hardness of sintered friction materials decreases. With the addition of Mo, the wear amount of the friction material first decreases and then increases. When the mass fraction of Mo added to the sintered friction material is 12%, the wear rate of the material is lower than that of other samples, and it has good wear resistance. Adding Mo element to iron copper based friction materials improves the wear resistance of sintered friction materials due to the strengthening effect of Mo.

Effect of Mo content on microstructure and corrosion behavior in HCl of ultra-high strength maraging steels

Maraging steels are one of the highest strength steels commercially available. The new versions are known as ultra-high strength maraging (UHSM) steels and can offer yield strength values over 3 GPa. The aim of this investigation was evaluating the electrochemical behavior of three non-commercial/laboratory UHSM steels containing 13Ni–15Co and Mo content variations (7.5, 11 and 15 wt%). The UHSM steels were annealed at 1000 °C and studied at different conditions (non-aged and aged at 480 °C for 3 h and 6 h). As reference material, a commercial maraging steel (18Ni–9Co–5Mo) heat treated according to typical recommendations (annealed at 820 °C for 1 h and aged at 480 °C for 4 h) was used. The UHSM presented considerable higher hardness than commercial maraging. Comparing between the UHSM steels, the samples treated for 6 h do not contribute to increase the hardness when compared to those of 3 h. The electrochemical tests in hydrochloric aqueous solution showed that commercial maraging steel and the UHSM containing most Mo (11 wt%) aged by 6 h presented the worst corrosion resistance while the best performance was obtained by the samples with 7.5 and 11 wt% Mo aged for 3 h.

Effects of Mo content on the microstructure and mechanical properties of laser cladded FeCoCrNiMox (x = 0.2, 0.5) high-entropy alloy coatings

The laser cladding additive manufacturing technology and high-entropy alloys can serve as ideal techniques and materials for the surface repair of high-speed train axles. Coatings of FeCoCrNiMox (x = 0.2, 0.5) were prepared on EA4T axle steel using laser cladding technology, and their phase, structure, and mechanical properties were analyzed using X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) characterization techniques. Additionally, the mechanical properties of the coatings were tested, and first-principles calculations were used to verify and calculate the material's mechanical performance. The research findings indicate that an increase in Mo content leads to a greater degree of lattice distortion, causing a leftward shift in diffraction peak positions. Significant differences in the microstructure from the substrate to the coating surface were observed, with columnar grain structure at the bottom of the cladding layer and equiaxed dendrites dominating the coating surface. The increase in Mo content promotes the formation of σ phase while also refining the grain size. ECCI results show that both types of coatings consist of a high-density dislocation cell structure and Mo-rich particles. With an increase in Mo content, the peak hardness of the coating increased from 456.5 HV to 469.4 HV, while the impact energy decreased from 56 J to 16 J, attributed to the increase in dislocation density and the greater quantity of σ phase. First principles calculations verified that the comprehensive mechanical properties of FeCoCrNiMo0.2 are superior, providing theoretical guidance for the optimization and design of the coatings.

Effect of Mo on the σ-phase precipitation behavior of super-austenitic stainless steel

The aging precipitation behavior of super-austenitic stainless steels 904L (4.32% molybdenum (Mo)), 254SMo (6.06% molybdenum) and AL-6XN (6.29% molybdenum) with different molybdenum contents at 800–900°C was investigated by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The effect of molybdenum content on the σ-phase precipitation behavior of commonly used super-austenitic stainless steel was investigated. The results show that the super-austenitic stainless steels with different molybdenum contents formed different numbers and shapes of σ phases in the isothermal aging process, and the number of σ phases of 254SMo and AL-6XN is much larger than that of 904L, and the shape of the σ phases mainly shows coarse acicularity and elongation, while the σ phases of 904L show fine granularity.

Effect of Mo content on the corrosion resistance of (CoCrFeNi)1−xMox thin films in sulfuric acid

(CoCrFeNi)1−xMox thin films with various Mo content (0–10 at.%) were grown by magnetron sputtering on a stainless steel substrate. The films with 0–2 at.% presented two crystal structures: one FCC phase and one sigma phase, while films with higher Mo content only had the FCC structure. All films have a (111) texture and follow the topography of the substrate. The corrosion resistance of the films was evaluated in 0.05 M H2SO4 at room temperature and at 80 °C. It was observed that the corrosion current densities considerably decreased for Mo > 2 at%, and that the current densities were higher at the elevated temperature. Scanning Kelvin Probe Force Microscopy showed a large potential difference between the main FCC phase and sigma phase for the Mo0–2 films. This would suggest that preferential dissolution of the FCC phase occurs over the sigma and reduces the corrosion resistance. Such preferential dissolution does not occur for the higher Mo content films with only the FCC phase. The high corrosion resistance was also attributed to the inhibition of Fe and Cr dissolution by Mo and the stabilisation of the Cr enriched oxide by incorporating Mo oxides into the passive film, identified by X-ray photoelectron spectroscopy. The low corrosion current densities (below 1 µA/cm2) make these thin films possible candidates for protective coatings of bipolar plates in PEM fuel cells.

Effects of molybdenum addition to activated carbon supported Ni‐based catalysts for CO2 methanation

AbstractRecently, CO2 methanation has become a technique that aims to reduce anthropogenic CO2 emissions by converting CO2 captured from stationary and mobile sources and H2 produced from renewable sources into CH4. Due to their excellent performance‐to‐cost ratio, Ni‐based catalysts were frequently used in such conversions. The main drawbacks, however, are that Ni has the propensity to aggregate and deposit carbon during the high‐temperature reaction. These issues can be partially resolved by including a support (e.g., MOF, zeolite, activated carbon, etc.) and a second transition metal (e.g., Mo, Co, or Fe) in Ni‐based catalysts. Therefore, the activity of Ni‐based catalysts at low temperatures needs to be improved. In this study, a series of mesoporous activated carbon (AC) supported bimetallic Ni–Mo catalysts (Ni–xMo/AC, Ni = 13 wt.%, x = 5, 7, 9, 11 wt.%) were synthesized using the incipient wetness impregnation method. The effect of Mo content on the catalyst's activity was examined in a fixed‐bed reactor. At 250–650°C, 1‐atmosphere pressure, gas hourly space velocity (GHSV): 1200 mL h−1 g−1, and H2/CO2 ratio: 4:1, the catalytic efficiency of these catalysts was examined. The catalysts were analyzed using transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), X‐ray powder diffraction (XRD), N2‐physisorption, and scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM‐EDX). Ni–7%Mo/AC catalyst showed the lowest carbon deposition rate, superior stability, and the best activity. The addition of Mo can improve the heat resistance of the Ni/AC catalyst and the interaction between the metal nickel and the support, which prevents the sintering of the catalyst. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Effect of Mo content on the microstructure and mechanical properties of CoCrFeNiMox HEA coatings deposited by high power impulse magnetron sputtering

In this work, CoCrFeNiMox high entropy alloy (HEA) films were deposited by High Power Impulse Magnetron Sputtering (HiPIMS) using pure Mo and equiatomic CoCrFeNi targets. The effect of Mo content on the microstructure, residual stress state, and mechanical properties of the films was investigated in the range of 0–20 at.%. All films exhibited a columnar growth morphology and a high density of planar defects. Increasing the Mo content promoted the formation of a fine-grained structure and induced the transformation from a single face-centered cubic (FCC) phase to a mixture of FCC and body-centered cubic (BCC) phases. All produced films displayed a compressive residual stress state regardless of the Mo concentration. In terms of mechanical properties, the hardness of the films increased with increasing Mo content due to solid solution and grain boundary strengthening, along with the formation of a hard BCC phase. On the other hand, the elastic modulus decreased, likely due to the formation of an amorphous phase at higher Mo concentrations.

Passivation and localized corrosion resistance of Al0.3Cr0.5Fe2MoxNi1.5Ti0.3 compositionally complex alloys: Effect of Mo content

Al0.3Cr0.5Fe2MoxNi1.5Ti0.3 (x = 0, 0.05, 0.15) FCC+L21 compositionally complex alloys are investigated using electrochemical and surface science methods in 0.1 M Na2SO4 and 0.1 M NaCl at pH 4 and 10. Mo is mainly found in the FCC phase and amplifies Al and Ti partitioning. The passive film is enriched in Cr(III), Ti(IV), Mo(IV)/Mo(VI), and (at pH 4) Al(III) with elemental fates tracked during film formation and dissolution. Mo presence does not enhance Cr or Ni passivation, instead promoting Ti(IV). Pitting and repassivation potentials increase at higher Mo concentrations, suggesting improved resistance to localized corrosion often initiated at FCC-L21 interfaces.

Effect of Mo Content on Friction and Wear Properties of Fe-Mn-Al-C Alloys Under Different Working Conditions

For this study, Fe-25Mn-9Al-8Cr-1C-xMo alloys (x = 0, 0.1, 0.2, 0.3, 0.4 wt%) were prepared by mechanical alloying combined with vacuum hot-pressing sintering. The corresponding microstructure, mechanical properties, and friction and wear properties under different working conditions (dry friction, oil lubrication and sulfur-containing boundary lubrication) of materials were studied. The results show that the Fe-25Mn-9Al-8Cr-1C alloy is mainly composed of the austenite phase, Cr7C3 phase, and a small amount of a-Al2O3 phase. After adding Mo element, the Fe2MoC phase appears. With the increase of Mo content, the tensile strength and elongation of the alloys increase first and then decrease. In particular, when the Mo content is 0.3 wt%, an excellent combination of strength and toughness is obtained. The product of strength and elongation of the Fe-25Mn-9Al-8Cr-1C-0.3Mo alloy reaches a maximum value of 3.69 GPa·%, which is improved by 158.04% compared with the matrix alloys. With the increase of Mo content, the average friction coefficient and volume wear rate of the alloys show a trend of first decreasing and then increasing under different working conditions. Also, the average friction coefficient and volume wear rate of the alloy with 0.3 wt% Mo reach a minimum value, especially under the condition of sulfur-containing boundary lubrication. The average friction coefficient and volume wear rate of Fe-25Mn-9Al-8Cr-1C-0.3Mo alloy are 0.051 and 0.222 × 10−4 mm3·N−1·m−1, respectively, which are 40.69% and 46.38% lower than those of the matrix alloys.

Effect of Mo content on interfacial microstructure and properties of explosive welded Mo–Cu/Cu plates

In this study, Mo–Cu/Cu plates were successfully fabricated by explosive welding and the influence of Mo content on their interfacial microstructure, shear strength, thermal conductivity and electrical conductivity was investigated. The results showed that as the Mo content increased to 70 wt%, the number of serrations at the interface of the Mo70Cu30/Cu plate increased, exhibiting a more complete shape and periodically ordered arrangement. In addition, increasing the Mo content to 70 wt% leads to a significant improvement in the interdiffusion distance at the interface, resulting in significant improvements in shear strength, thermal conductivity and electrical conductivity compared to the corresponding Mo70Cu30 plate. More serrations, more complete serrations and periodically arranged serrations benefit from increased Mo content to 70 wt% while improving the shear strength, thermal conductivity and electrical conductivity compared to raw material of Mo–Cu plate.

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.

Effect of Mo content on the passivation and localized corrosion behavior of laser engineered net shaped (LENS) Co-Cr-Mo alloys in a simulated physiological solution

Effect of Mo content on the passivation and localized corrosion behavior of laser engineered net shaped (LENS) Co-Cr-Mo alloys in a simulated physiological solution

Insight into the Role of Mo Content on the Microstructure and Impact Toughness of X80 Thick-Walled Low-Temperature Pipeline Steel

In this manuscript, the effects of Mo content on the microstructure and impact toughness of X80 thick-walled low-temperature pipeline steel were studied. Two test steels with different Mo content (0.25% and 0.40%) were prepared by the thermo-mechanical control process. The impact properties were measured at −45 °C, and the microstructure evolution was observed via an optical microscope (OM), a scanning electron microscope (SEM), electron back-scattered diffraction (EBSD), and a transmission electron microscope (TEM). Each steel showed the formation of a mixed microstructure consisting of polygonal ferrite (PF), granular bainite (GB), and lath bainite (LB). Increasing Mo content resulted in the rise of LB at the expense of PF and GB. At the same time, the morphology of martensite/austenite (M/A) constituents changed from blocky to slender. The dislocation density in the ferrite matrix around the M/A constituents enhanced with an increase in Mo content. This also led to an increase in the microstrains around the M/A constituents. Also, the number fraction of the high angle grain boundary (HAGB) (MTA > 15°) decreased with the addition of more Mo content. Furthermore, with an increase in Mo content from 0.25% to 0.40%, the low-temperature impact toughness decreased from 206 to 57 J. Both an increase in the slender M/A constituents and a decrease in the HAGB number fraction deteriorated the low-temperature impact toughness of the X80 thick-walled low-temperature pipeline steel.

Effect of Mo content on oxidative dehydrogenation of propane with CO2 over ZnOx catalysts supported on Mo–Zr mixed–oxides

The production of propylene from readily available propane sources is of great importance as it serves as a crucial building block for producing numerous value-added chemicals. Oxidative dehydrogenation of propane with carbon dioxide (ODPC) has been proposed as a viable and eco-friendly approach for simultaneous propylene production and carbon dioxide reduction. In this study, ZnOx catalysts were prepared by supporting them on a range of molybdenum–zirconium (Mo–Zr) mixed–oxides with varying Mo contents, aiming to utilize them for ODPC applications. The incorporation of suitable quantities of Mo in zirconium dioxide (ZrO2) supports increases the surface concentration and enhances the dispersion of ZnOx, thereby demonstrating promotional effects on the surface properties of the supported ZnOx catalysts. Notably, the ZnOx catalyst supported on a Mo–Zr mixed–oxide, with an optimized Mo content, exhibits a propane conversion rate more than two-fold higher than that of the catalyst without Mo in ODPC. Furthermore, the introduction of Mo into the ZrO2 supports effectively inhibits the formation of coke by suppressing the cleavage of C–C bonds in propane. In comparison, the supported ZnOx catalysts with higher Zn loadings, show that a Mo–Zr mixed–oxide support effectively suppresses the formation of bulk ZnOx more than an unmodified ZrO2 support, leading to improved ODPC performance. The promoting effects of Mo emphasize the potential of utilizing mixed–oxide supports for ZnOx catalysts in ODPC, demonstrating a promising opportunity for enhancing catalytic performance.

Microstructure, wear and corrosion behavior of high-entropy alloy coatings: The concentration of Mo element and the dual effect of σ-CrMo phase

In this work, LaB6/FeCoNiCrMoX (X = 0, 0.3, 0.6 and 1) high-entropy alloys coatings with different Mo contents were prepared on the Ti6Al4V substrate by laser cladding technology. The effect of Mo content on the microstructure, microhardness, friction and wear, and electrochemical properties were investigated. The results indicated that the increase of Mo element enhanced the lattice distortion effect, and σ-CrMo phase is generated at X = 0.6 and 1. Benefiting from the strength of σ-CrMo phase, the mechanical properties of the coating have been significantly improved. At X = 1, the microhardness of Mo1.0 coating was the highest (987 HV0.3), and compared to the Mo0 coating, the wear volume of Mo0.3, Mo0.6, and Mo1.0 were lower, with values of 5.01, 1.47, and 0.54 μm3, respectively. The appropriate content of Mo element significantly improved the corrosion resistance of the coating. The corrosion current density of Mo0, Mo0.3, Mo0.6, and Mo1.0 coatings were 2.045 × 10−5, 8.873 × 10−6, 1.641 × 10−6, 2.164 × 10−6, 1.641 × 10−6 A·cm−2, respectively. As the Mo content increased, the thickness of the passivation film increased, reaching the maximum value (6.915 nm) at X = 0.6. However, excessive Mo (X = 1.0) content led to crack initiation, disrupting the stability of the passivation film, and the thickness of the passivation film actually decreases (4.162 nm). The research in this work provided a theoretical basis for the composition design of high entropy alloys regarding Mo content.

Effect of Mo content on the microstructure, superplastic behavior, and mechanical properties of Ni and Fe-modified titanium alloys

Novel titanium-based alloys are required to increase the efficiency of superplastic forming technology and decrease energy consumption. For this purpose, the superplastic deformation behavior, strain-induced microstructure evolution in a temperature range of 625–775 °C, and post-deformation mechanical properties of Ti–4Al–1V–1Fe–1Ni-0.1B-xMo alloys (x = 1, 2.5, or 5 wt%) were investigated. The studied alloys demonstrated a stable flow with a high strain rate sensitivity coefficient m of 0.50–0.65 and an elongation-to-failure δ of 700–1000% at temperatures of 700–775 °C. Molybdenum insignificantly influenced superplastic deformation behavior at high temperatures due to a high fraction of the β phase of 22–62%. The Mo effect was significant at a low deformation temperature of 625 °C. At this temperature, an increase in Mo content from 1 to 5% provided the β-phase fraction above the critical value of ∼20% and increased the m-value from 0.4 to 0.5 and δ from ∼200 to ∼700%. Increasing Mo from 1 to 5% enhanced the post-deformation yield strength at room temperature by 180 MPa, the ultimate tensile strength by 170 MPa, and the ductility by 2.5%. Consequently, alloying Ti–4Al–1V–1Fe–1Ni-0.1B with 5% Mo provided an excellent combination of superplasticity at a low temperature of 625 °C and post-forming tensile mechanical properties.