Effect Of Mo Addition Research Articles

Effects of Mo Addition on Microstructure and Corrosion Resistance of Cr25-xCo25Ni25Fe25Mox High-Entropy Alloys via Directed Energy Deposition.

Highly entropy alloys (HEAs) are novel materials that have great potential for application in aerospace and marine engineering due to their superior mechanical properties and benefits over conventional materials. NiCrCoFe, also referred to as Ni-based HEA, has exceptional low-temperature strength and microstructural stability. However, HEAs have limited corrosion resistance in some environments, such as a 3.5 wt% sodium chloride (NaCl) solution. Adding corrosion-resistant elements such as molybdenum (Mo) to HEAs is expected to increase their corrosion resistance in a variety of corrosive environments. Metal additive manufacturing reduces production times compared to casting and eliminates shrinkage issues, making it ideal for producing homogeneous HEA. This study used directed energy deposition (DED) to create Cr25-xCo25Ni25Fe25Mox (x = 0, 5, 10%) HEAs. Tensile strength and potentiodynamic polarization tests were used to assess the materials' mechanical properties and corrosion resistance. The mechanical tests revealed that adding 5% Mo increased yield strength (YS) by 20.1% and ultimate tensile strength (UTS) by 9.5% when compared to 0% Mo. Adding 10% Mo led to a 32.5% increase in YS and a 20.4% increase in UTS. Potentiodynamic polarization tests were used to assess corrosion resistance in a 3.5-weight percent NaCl solution. The results showed that adding Mo significantly increased initial corrosion resistance. The alloy with 5% Mo had a higher corrosion potential (Ecorr) and a lower current density (Icorr) than the alloy with 0% Mo, indicating improved initial corrosion resistance. The alloy containing 10% Mo had the highest corrosion potential and the lowest current density, indicating the slowest corrosion rate and the best initial corrosion resistance. Finally, Cr25-xCo25Ni25Fe25Mox (x = 0, 5, 10%) HEAs produced by DED exhibited excellent mechanical properties and corrosion resistance, which can be attributed to the presence of Mo.

Effect of Mo addition on microstructure and mechanical properties of Cu-12.5Ni-5Sn alloy

Cu-12.5Ni-5Sn-xMo (x=0, 0.5, 1.0, 1.5 wt%) alloys were prepared using Spark Plasma Sintering (SPS) technology. The effect of Mo addition on the microstructure and mechanical properties of Cu-12.5Ni-5Sn alloy was investigated. The results indicate that adding trace amounts of Mo significantly refines the grain structure of Cu-12.5Ni-5Sn alloy, attributed to the formation of Mo-rich phases. Mo addition also inhibited the growth of discontinuous precipitation (DP) after aging treatment, reducing the DP volume fraction from approximately 25 % to 6 %. This effect is attributed to the precipitation of micron-sized Mo-rich phases at grain boundaries, which inhibit DP nucleation and growth by occupying γ-phase nucleation sites and pinning grain boundaries, thus impeding grain boundary diffusion. In addition, the interlamellar spacing of the discontinuous precipitation increases and the growth rate of lamellae decreases with increasing Mo content. Furthermore, an optimized combination of hardness (310 HB) and yield strength (586 MPa) was achieved in the Cu-12.5Ni-5Sn-1.0Mo alloy after aging treatment.

New insights of the microcrack initiation induced by Mo addition in Ni-based single crystal superalloys during creep at 900 °C

Mo has received much attention in Ni-based single crystal superalloys as a main strengthening element at elevated temperatures above 1000 °C. However, the effects of Mo addition in new generation single crystal superalloys at medium temperature conditions are still not clear. This paper investigated the creep property at 900 °C and 392 MPa in a 4th generation Ni-based single crystal superalloy with different Mo contents, indicating that Mo addition decreased the creep life and induced large amounts of microcracks. Higher Mo content could weaken the interface strength by inducing more stacking faults, causing crack initiation along the interface. The elemental segregation along the stacking faults triggered the nucleation of other precipitates, which could further lead to cracks. The precipitation of topologically close-packed (TCP) phases introduced by more Mo addition caused crack initiation along the interfaces between the TCP phases and γ′ phase. By investigating the microcrack formation induced by Mo during creep at 900 °C, we provided a new perspective for the alloy design.

Experimental investigation and thermodynamic analysis of TiC–Fe cermets with Mo additions

Abstract In this study, the effects of Mo additions on the microstructure, hardness and bending strength of TiC–Fe cermets manufactured by spark plasma sintering were investigated by scanning electron microscopy, X-ray diffraction and mechanical properties tests. Thermodynamic calculations were utilized to analyze the evolution of the microstructure. The results show that the conventional core/rim structure was not formed during the solid-phase sintering of TiC–Fe cermets. The heat-treatment process and reasonable Mo addition can effectively enhance the overall performance of the alloys. With the addition of minor Mo, the hardness of the sintered cermets improved significantly, which was attributed to the solid solution strengthening mechanism of Mo in Fe binder. However, excessive Mo exceeded the solubility range of Fe binder and precipitated in the form of M 6C and Mo2C phases, which damaged the bending strength of the heat-treated cermets.

Effect of Mo on the Corrosion Resistance of Cr-Containing Steel in a Simulated Tropical Marine Atmospheric Environment

In this manuscript, the effect of Mo addition on the corrosion resistance of the low-alloy steel in a simulated tropical marine atmospheric environment has been studied through microstructure characterization, corrosion immersion experiments, electrochemical measurement, and a series of microscopic characterization methods. The results show that Mo has the ability to reduce the corrosion rate of low-alloy steel in a marine atmospheric environment, with a more pronounced reduction effect observed over longer corrosion periods. The addition of Mo enhances the corrosion product film’s compactness when coupled with Cr, subsequently improving corrosion resistance. Simultaneously, MoO42−, acting as a slow-release ion, can effectively suppress localized corrosion in low-alloy steel. The research findings can offer data support and a theoretical foundation for the design of low-alloy steels with enhanced corrosion resistance in a tropical marine atmospheric environment.

Effect of Mo addition on interfacial microstructure and mechanical property of SiC joint brazed by an Ni–Si filler

AbstractNi‐based alloys provide good brazing filler characteristics for the many applications of SiC ceramics. Nevertheless, the presence of graphite is unavoidable in the reaction between Ni and SiC, leading to a significant degradation of the mechanical properties of the joint. This study investigates the effect of Mo in Ni–30Si alloy on the brazing of SiC at 1300°C, to regulate interfacial reactions and reduce residual stresses by decreasing overall coefficient of thermal expansion (CTE) values throughout the brazing process. The addition of Mo up to 8 at.% efficiently suppresses graphite accumulation by converting it into Mo2C + Ni3Mo3C phases and lowering the CTE to 5.4 × 10−6/°C. When the Mo loading exceeds 12 at.%, the interactions between the filler and SiC are reduced as a result of the non‐homogeneous dispersion of Mo. The experimental findings indicate that the joint without graphite has a lap shear strength of 107 MPa, which is nearly three times greater than the joint with graphite. Thermodynamic analyses are performed to provide a comprehensive understanding of the underlying mechanisms responsible for the formation of distinct phases in brazed joints.

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

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.

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

Effect of Mo Additions on the Physical, Mechanical and Corrosion Properties of Commercially Pure Ti Fabricated by Metal Injection Moulding

Effect of Mo Additions on the Physical, Mechanical and Corrosion Properties of Commercially Pure Ti Fabricated by Metal Injection Moulding

Effect of Mo addition on nanoindentation creep behavior of FeCoBSiNb bulk metallic glasses

Novel Fe52Co20-xB20Si4Nb4Mox (x = 0–5) bulk metallic glasses with a diameter of 2 mm are successfully prepared by vacuum suction casting and the effect of Mo addition on their nanoindentation creep behavior is studied. Through a differential scanning calorimetry and creep compliance spectral analysis, it is found that the addition of a small amount of Mo increases the enthalpies (ΔH) and free volumes of the alloys. These factors stimulate the rearrangement of the atomic structures of the alloys and induce the adjustment of their internal structure, resulting in a relatively loose atomic packing state that allows the alloys to provide a continuous response to stress during creep deformation. By analyzing the unloading and load holding sections on the load-displacement curves, it is shown that the hysteresis of deformation induces the displacement jump phenomenon and the amplitude of the jump is inversely proportional to the equivalent stress. The larger the equivalent stress, the less obvious the displacement pop-out phenomenon. The changes in strain rate sensitivity exponent (m) and hardness are also studied. Combined with a delay spectral analysis, it is found that a 5% Mo addition significantly improves the creep resistance of the alloys.

Effect of Mo addition on microstructure and wear resistance of laser clad AlCoCrFeNi-TiC composite coatings

As a typical wear-resistant material, TiC particle-reinforced AlCoCrFeNi composite coatings have great advantages. In this work, the Mo was added to AlCoCrFeNi-TiC coatings to further improve the wear resistance, which were fabricated as AlCoCrFeNiMox-TiC (x: molar ratio; x = 0, 0.2, 0.5, 0.8) composite coatings by laser cladding. The microstructure evolution, hardness, and wear resistance were investigated in detail. The results show that a ring of (Ti, Mo)C phase is formed in the outer layer of TiC particles due to the substitution of Mo atoms. Based on the first-principles calculations, the lattice constant of (Ti, Mo)C phase is 4.328 Å, slightly smaller than that of TiC. More importantly, Mo can significantly reduce the interface energy from 0.27 J·m−2 to − 0.18 J·m−2, thus improving the interface stability. The coating matrix (CM) exhibits a spinodal structure of B2 + σ phase, caused by the generation of σ phase. The σ phase has a calculated hardness of about 15.3 GPa, which is undoubtedly conducive to wear resistance of the CM. With the addition of Mo, the hardness of composite coating increases from 611.9 HV0.3 to 822.6 HV0.3. All the coatings present high wear resistance, as evidenced by the abrasive wear mechanisms.

Effect of Mo-addition over a large enhancement of the hydrogen evolution reaction in WC/rGO nanocomposite

We report a large enhancement of the hydrogen evolution reaction in WxC/rGO nanocomposite by adding Mo to the composite. The mixed transition metal carbide (WxC-MoxC/rGO) nanocomposite was prepared by a liquid phase reaction followed by a high temperature (900 °C) annealing processes that led to the crystallization of WxC, MoxC and simultaneous reduction of graphene oxide to reduced graphene oxide (rGO). The WxC-MoxC/rGO (Mo = 0.25 g) catalyst achieved very good hydrogen evolution reaction with an overpotential of −170 mV at 10 mA and a Tafel slope of 76 mV dec−1 indicating the suitability of this composite for the hydrogen production.

Effect of Mo addition on thermal stability and magnetic properties in FeSiBPCu nanocrystalline alloys

The glass forming ability, thermal stability, microstructure, and magnetic properties of Fe83.3(Si4B8P4)16−xCu0.7Mox (x = 0, 0.5, 1, and 1.5) alloys are studied to investigate the influence of Mo addition. With increasing Mo content, the negative mixing enthalpy (ΔHmix) increases and the Delta parameter (δ) decreases, which leads to a decline in the glass forming ability. The secondary crystallization temperature increases continuously with increasing Mo content. A small amount of Mo improves sufficiently the thermal stability of the alloy system, which can bear higher temperatures (up to 520 °C) for longer time (up to 40 min) without the formation of compounds because of their increased activation energy. The saturation magnetic flux density (Bs) decreases from 1.78 to 1.68 T with increasing Mo content as a result of the lower volume fraction of the α-Fe phase. Optimum magnetic properties with Bs = 1.74T and Hc = 8.2A/m are achieved in Fe83.3(Si4B8P4)15Cu0.7Mo1 ribbon.

Effects of Mo alloying on the microstructure and wear resistance of Fe–B surfacing alloys

The effect of Mo addition on microstructure, impact property, and wear resistance of high boron Fe-4.5 wt% B surfacing alloy, which was developed by the three-arc double-wire welding method was investigated in this work. The phase structure and microstructure of the surfacing alloy were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Electron Backscattered Diffraction (EBSD). Besides, a two-body abrasive wear test and impact fracture test was carried out to study the wear behavior and fracture mechanism of the surfacing alloy. The results show, hypereutectic Fe-4.5 wt% B surfacing alloys with different Mo additions are mainly composed of primary (Fe, Mo)2B boride, eutectic matrix, and FeMo2B2. With the increase of Mo content in Fe-4.5 wt% B surfacing alloy, the continuous growth of the eutectic structure is blocked, which can inhibit the formation and expansion of cracks in the surfacing layer. With the increase of Mo, the wear resistance of Fe-4.5 wt% B alloy increases from 16.70 g-1 to 22.72 g-1. In the impact fracture experiment, Fe-4.5 wt% B surfacing alloy has high brittleness, the primary Fe2B is a transgranular fracture, and the interface between primary Fe2B boride and eutectic structure is an intergranular fracture. With the addition of Mo, the fracture mechanism of the surfacing alloy changes from transgranular fracture to transgranular fracture + ductile fracture, which reduces the fragmentation and spalling during the wear process, thereby improving its wear resistance.

The Effect of Molybdenum Fertilizer on the Growth of Grass–Legume Mixtures Related to Symbiotic Rhizobium

Molybdenum (Mo) is required by the enzymes involved in many metabolic processes related to plant growth and development. However, the effects of Mo addition on plant growth and beneficial microorganisms in mixed grasslands are unclear. We conducted a greenhouse experiment to examine the effects of different Mo addition levels (10 and 20 mg Mo kg−1 soil in the form of Na2MoO4) on the growth of perennial ryegrass–white clover in two low-Mo soils, as well as their symbiotic microorganisms. Our results showed that the addition of Mo had a significant impact on plant growth in limestone soil but not in yellow loam soil (p < 0.05). Compared with no addition of Mo fertilizer in limestone soil, an addition of 10 mg Mo kg−1 significantly increased the plant community shoot and root biomass (p < 0.05). However, this improvement was not observed with an addition of 20 mg Mo kg−1. The shoot nitrogen and phosphorus content in both soil types was unaffected by the Mo addition (p > 0.05), whereas the 10 mg Mo kg−1 addition significantly increased the shoot nitrogen and phosphorus uptake in limestone soil (p < 0.05). This increase in plant community productivity was primarily due to the increased growth of both species, caused by the enhanced activation of the symbiotic rhizobium. We conclude that Mo supply may promote N utilization and uptake in mixed grassland by increasing the activity of symbiotic rhizobium, resulting in a higher yield of mixed grassland, which is critical for sustainable agricultural development in low-Mo soils.

Effect of Mo addition on the microstructural evolution and mechanical properties of Fe–Ni–Cr–Mn–Al–Ti high entropy alloys

High-strength alloys are in urgent demand for engineering applications. Inducing multiple strengthening phases in a ductile matrix by microalloying is an effective alloy-strengthening strategy, especially the simultaneous formation of geometrically close-packed (GCP) phases and topologically close-packed (TCP) precipitation in high entropy alloys (HEAs). In this study, the microstructural evolution and mechanical properties of a series of (FeNi)67Cr15Mn10-xAl4Ti4Mox HEAs with x values of 1, 2, 3, 4, and 5 were analyzed in detail, with the substitution of Mn by Mo. This substitution does not change the L12 phase forming elements (Ni, Al and Ti) in the alloy, and enhance the σ phase precipitation, which meantime does not modify the oxidation resistance in thermal mechanical treatment. After aging at a temperature of 1023 K for 5 h, the matrix of the HEAs still maintains a face-cubic-centered structure. However, as Mn is replaced by Mo, hard σ precipitates are introduced into the matrix and the grains are significantly refined when x < 5. Therefore, the yield strength monotonically increases with increasing x. However, the formation of the hard σ precipitates also hinders the sustainability of the work hardening process, and thereby decreases the plasticity of the HEAs. Hence, the elongation at break monotonically decreases with increasing x. However, the high density of σ phase precipitates obtained at x = 5 prematurely terminates the work hardening process. Therefore, the highest ultimate tensile stress is obtained at x = 4, rather than x = 5. This also changes the fracture morphology from a coarse grain morphology for x < 5 to a typical brittle fracture at x = 5. Accordingly, (FeNi)67Cr15Mn6Al4Ti4Mo4 obtains the optimal mechanical properties overall.

Effect of Mo Addition on the Austenite Stability of Nanocrystalline Fe-7wt.%Mn Alloy Fabricated by Spark Plasma Sintering

Effect of Mo Addition on the Austenite Stability of Nanocrystalline Fe-7wt.%Mn Alloy Fabricated by Spark Plasma Sintering