Mo Alloy Research Articles

Corrosion resistance investigation of the Ti–Al–Mo system supported by CALPHAD approach and key experiments

The corrosion resistance of Ti–Al–Mo alloys in seawater were investigated by thermodynamic calculations and electrochemical tests. Four as-cast alloys were designed based on thermodynamic calculations. The calculated results were verified by experimental determination. The Gibbs energy and electrochemical experiment results showed Ti55Al40Mo5 alloy has the most positive Gibbs energy and the best corrosion resistance. The bcc(Ti) phase has best corrosion resistance among AlTi, AlTi3 and bcc(Ti). The present work further proves the important role of phase diagram calculation in alloy design, and thermodynamic database provides important theoretical support for efficient development of new alloys.

Microstructures and Tensile Properties of Ti-6Al-4 V-(0, 2.5, 5, 7.5)Mo Alloys Manufactured by Metal Injection Molding

Microstructures and Tensile Properties of Ti-6Al-4 V-(0, 2.5, 5, 7.5)Mo Alloys Manufactured by Metal Injection Molding

Material design using calculation phase diagram for refractory high‐entropy ceramic matrix composites

AbstractTo achieve Si‐free refractory ceramic matrix composites exposed to an oxidizing atmosphere at approximately 2000°C, a Ti–Zr–Mo ternary alloy melt‐infiltration (MI) method was developed for the production of carbon fiber‐reinforced refractory high‐entropy ceramic matrix composites (C/RHECs), with high‐entropy carbides serving as the matrix. This approach was designed using calculation phase diagrams (CALPHADs) and the calculation of thermodynamic parameters. The combination of CALPHAD and the calculation of alloy and carbon reactivity enabled the prediction of reaction and infiltration behavior into a preform comprising carbon fiber, carbon black, and transition metal carbide powders. Furthermore, C/RHECs featuring a (Ti, Zr, Hf, Nb, Ta, Nb, Mo)C matrix were experimentally fabricated through the Ti–Zr–Mo alloy MI method in accordance with the design. The arc‐wind tunnel tests on the C/RHECs conducted at approximately 2000°C revealed surfaces covered with complex oxides. The apparent oxidation rate of the C/RHECs was similar to that of Si‐containing ceramics and composites. These results indicate that complex oxides act as a barrier to oxygen diffusion toward unoxidized regions, making Si no longer essential for protecting materials from oxidation above 2000°C.

Corrosion studies on pulse reverse Ni–Mo coatings electrodeposited on Cu substrate

This study conducts a thorough analysis of Ni–Mo coatings electrodeposited on copper substrates, assessing the corrosion resistance of the coated system in a 3.5 M NaCl solution. It focuses on how deposition methods and anodic current densities affect both the coating's integrity and its ability to protect the substrate from corrosion. Three distinct techniques were employed to form Ni–Mo coatings: Direct Current (DC), Pulse Current (PC), and Pulse Reverse Current (PRC). Notably, coatings fabricated using the PRC method demonstrated significant morphological and corrosion behavioral variations compared to their DC and PC counterparts. Emphasis was placed on the role of porosity type and grain boundaries of the coatings, in addition to their composition, highlighting their considerable influence on corrosion dynamics. The standout performer was the one electrodeposited at the supreme anodic current density of 200 mA.cm⁻², exhibiting a composition of 25.2 wt% Mo, 57.4 wt% Ni, and 17.4 wt% O, and incorporating Ni–Mo alloy with oxide and hydroxide phases along with a small average grain size of less than 192 nm. The findings underscore the PRC method's efficacy in producing optimized Ni–Mo coatings, highlighting its broad potential for enhanced corrosion resistance applications.

Effect of TiAlN diffusion barrier at MoSi2-SiO2 composite coating/Mo alloy interface

In order to reduce the interdiffusion at interface of the silicide coating/Mo alloy and improve the service life of the coatings. MoSi2-SiO2 composite coatings with TiAlN diffusion barrier were prepared on Mo alloy by magnetron sputtering and followed by hot press sintering in the present study. Oxidation and interdiffusion behaviors of the samples were investigated at 1200 °C in static air. The results show that MoSi2-SiO2 composite coatings have excellent high temperature oxidation resistance, and the inward diffusion of Si is greatly inhibited with the addition of TiAlN diffusion barrier. After oxidation at 1200 °C for 100 h, the mass change of the MoSi2-SiO2 composite coatings is only -0.059 mg/cm2 to -0.022 mg/cm2, the thickness of the interdiffusion zone is just only 3.4 μm that is one order of magnitude smaller than TiAlN-free coating. The TiAlN diffusion barrier can effectively inhibit the interdiffusion of elements between the MoSi2-SiO2 composite coatings and the Mo alloy substrates.

Exceptional thermal stability and mechanical properties of dual-phase amorphous-nanocrystalline Al–Mo alloy films

Dual-phase amorphous-nanocrystalline Al-x at.% Mo (x = 20, 26, 30) alloy films prepared in the way of dual-phase co-growth directly through magnetron sputtering were studied in terms of thermally induced microstructural evolution and mechanical properties via annealing at 550 °C. It was observed that, the annealed Al-26 and 30 at.% Mo alloy films maintained stable dual-phase amorphous-nanocrysatlline structure and precipitated Al8Mo3 nano-grains dispersed in amorphous matrix uniformly. After annealing, the surface roughness of Al-26 and 30 at.% Mo alloy films remained unchanged of 7.5 nm and the hardness and elastic modulus of them were as high as 13 and 210 GPa which enhanced about 50 % and 24 % than before, respectively. In contrast, the Al-20 at.% Mo alloy film crystallized completely and mainly contained intermetallic Al12Mo phase along with apparent grain coarsening after annealing, which resulted in significant increase of surface roughness and deterioration of hardness. The excellent thermal stability of dual-phase amorphous-nanocrystalline Al-26 and 30 at.% Mo alloy films stem from the small driving force for precipitated Al8Mo3 nano-grain growth, as well as benefit from effect of diffusion field impingement.

Subsequent growth and sequential twinning induced by the interaction of {332} twins in Ti[sbnd]15Mo alloy

The mechanisms associated with the interaction of {332} twins are investigated in metastable Ti15Mo alloy. There are 12 possible twin-twin junctions (TTJs) induced by {332} twins that can be classified into 5 types according to the crystallographic relation. Twin-twin interactions are accompanied with the formation of twin-twin boundaries (TTBs) on the acute side and obtuse side. Experimental results based on transmission electron microscopy (TEM) and procession electron diffraction (PED) show that subsequent growth of the TTBs is asymmetric with the twin thickening preferred only on one side for each type. Besides, it is observed that the twin-twin interaction could stimulate sequential {332} twinning inside the primary twin with a specific twin variant promoted. To account for the subsequent growth of the TTBs and the preferred selection of the sequential twinning variant associated with twin-twin interactions, the elastic energy analysis of the resultant dislocations at TTBs indicates that the growth of the TTBs is energetically favorable only on one side. Displacement gradient based analysis shows that the active sequential twin variant could maximumly accommodate the accumulated strain induced by the twin-twin interaction. This work is useful for predicting the preferential growth of the interfaces and the associated accommodation mechanisms induced by the interactions of localized shear bands.

Atomistic simulation of deformation twinning in nanocrystalline body-centered cubic U–Mo alloys

Deformation mechanisms of the nanocrystalline body-centered cubic U–Mo alloy were investigated through molecular dynamics simulations, focusing on the influences of the grain size and Mo content.

Effect of Gas Atmosphere in Aluminobarothermal Synthesis on the Structure of Metal Matrix Composites Based on Fe – Cr – Mn – Mo Alloy

Effect of Gas Atmosphere in Aluminobarothermal Synthesis on the Structure of Metal Matrix Composites Based on Fe – Cr – Mn – Mo Alloy

Corrosion Resistance, Composition, and Stratification of Passive Films: Ni-22Cr and Ni-22Cr-6Mo Alloys Passivated and Exposure Aged in Acidic Chloride Solutions

Ni-Cr based super-alloys have exceptional corrosion resistance, which is further improved with Mo alloying. The correlation between passive layer performance and composition was studied to gain a deeper mechanistic understanding of the role of Mo by comparing the behavior of Ni-22Cr to Ni-22Cr-6Mo (wt%) alloys. The passive layers were formed using galvanostatic holds to create fast and slow growth conditions using high and low current densities. A potentiostatic hold was added to initiate exposure aging. The passive film was characterized using electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), atomic emission spectro-electrochemistry (AESEC), and X-ray photoelectron spectroscopy (XPS). Combined electrochemical and XPS characterization offered insight in cation concentrations and stratification, bonding states (oxide, hydroxide), and their modulation as a function of electrochemical conditions and performance. Most importantly: (i) Mo addition enhanced Cr(III) bound in oxide, (ii) fast growth conditions resulted in less corrosion resistant films, and (iii) exposure aging increased Cr-enrichment and reduced stratification of Mo-cations. The correlation between passive film performance and Cr, Ni, and Mo oxidation states, bonding, oxide-hydroxide contributions, and stratification is discussed. Generally accepted correlations, such as Cr-cation concentration and performance of the passive layer, have to be reexamined in order to account for the complex chemical make-up of the passive layer.

Structure transformation induced bi-component Co–Mo/A-Co(OH)2 as highly efficient hydrogen evolution catalyst in alkaline media

Elucidating the inherent origins of the sluggish hydrogen evolution reaction (HER) kinetics in alkaline media and developing high-performance electrocatalysts are fundamental for the advances of conventional alkaline water electrolyzers and emerging anion exchange membrane (AEM) electrolyzers. Here we present a facile electrochemical modification strategy for the synthesis of bi-component Co–Mo(18%)/A-Co(OH)2 catalyst toward efficient HER catalysis in alkaline media. Porous Co–Mo alloys with adjustable Mo/Co atomic ratio are first prepared by H2-assisted cathodic electrodeposition. By virtue of the appropriate electronic structure and hydrogen binding energy, Co–Mo(18%) is the most HER active among the alloys and is further activated by a constant-current electrochemical modification process. Physical characterizations reveal the formation of amorphous Co(OH)2 nanoparticles on the surface. Electrokinetic analysis combined with theoretical calculations reveal that the in-situ formed Co(OH)2 can efficiently promote the water dissociation, resulting in accelerated Volmer-step kinetics. As a result, the Co–Mo(18%)/A-Co(OH)2 simultaneously achieves the optimization of the two factors dominating alkaline HER activity, i.e., water dissociation and hydrogen adsorption/desorption via the bifunctional synergy of the bi-components. The high HER activity (η10 of 47 ​mV at 10 ​mA ​cm−2) of Co–Mo(18%)/A-Co(OH)2 is close to benchmark Pt/C catalyst and comparable or superior to the most active non-noble metal catalysts.

Electrodeposited alloy electrodes in the Co–W–Mo system as highly efficient catalysts for hydrogen production from alkaline water electrolysis

In the presented paper the non-precious electrode materials containing Co, Mo, and W demonstrating high catalytic activity towards hydrogen evolution reaction were characterized. The studied alloy electrodes were electrodeposited from electrolytes with a simple composition, containing CoSO4, Na2WO4, Na2MoO4, and Na3C6H5O7. The structure, surface morphology, and composition of the prepared deposits were analyzed using scanning microscopy, X-ray diffraction, and transmission electron microscopy techniques. Cathodic polarization and electrochemical impedance spectroscopy were applied to assess the electrocatalytic activity and elucidate the HER mechanism in 1 M KOH solution. The nanocrystalline structure, fine grain size, and presence of microcracks on the surface of the studied alloys contributed to their notably high electrochemically active surface area (ECSA) (65.7e2, 11.7e4, and 99.7e3 cm2 for the Co–W, Co–Mo, and Co–W–Mo, respectively), a crucial factor driving their superior catalytic activity. The intrinsic catalytic activity evaluated at the overpotential of 150 mV was 9.2, 3.3, 0.78 and 1.4 μA cm-2 for the Co, Co–W, Co–Mo and Co–W–Mo electrodes, respectively. This indicates that the superior electrocatalytic characteristics observed for the alloy coatings, compared to Co resulted from the substantial increase in their ECSA. Among the investigated electrodes, the ternary Co–W–Mo alloy was characterized by the highest electrocatalytic performance confirmed by the lowest overpotential (42 mV) required to attain a current density of 10 mA cm−2.

Obtaining of Antibacterial Nanoporous Layer on Ti7.5Mo Alloy Surface Combining Alkaline Treatment and Silver: In Vitro Studies

In the present study, a combination of alkaline treatment and silver was used to produce an antibacterial nanolayer on the Ti7.5Mo alloy surface. The antibacterial response and osteogenesis were evaluated by assessing the adhesion and proliferation of S. aureus and S. epidermidis, as well as the adhesion, viability, and expression levels of genes involved in osteogenic differentiation in the mouse pre-osteoblast cell line MC3T3-E1. The potential stimulus of extracellular remodeling was evaluated using zymography. Our results showed that there is no difference in cytotoxicity after silver immobilization. Protein activity (MMP9) progressively increased for theTi7.5Mo alloy, both untreated and after alkaline treatment. However, the highest increase in protein activity was observed when the alloy was in direct contact with immobilized silver nanoparticles. The surfaces containing silver showed a better response in terms of colony formation, meaning that less bacterial adhesion was detected. The results showed that the layer formed was effective in reducing bacterial activity without altering cell viability.

Regularities in the Evolution of Thermoelastic Martensitic Transformations during Cooling/Heating in the Free State and under Load of Titanium Nickelide Alloyed with Niobium.

This article presents the results of studies of the features of the development of thermoelastic martensitic transformations during cooling/heating in the free state and under load of Ti50Ni49.7-XNbXMo0.3 alloys (X = 0.5, 1.0 and 1.5 at% Nb) with shape memory effects. Using X-ray diffraction analysis, it was found that all the alloys studied at room temperature contained a multiphase mixture consisting of intermetallic compounds with the TiNi (B2, B19'), Ni56Ti29Nb15, and Ti2Ni compositions. Scanning electron microscopy was used to study the microstructure of TiNi (Nb,Mo) alloys and it was found that the distribution of fine Ni56Ti29Nb15 particles in the matrix depends significantly on the concentration of the alloying element. A correlation was established between changes in the structural-phase state in TiNi (Nb,Mo) alloys and the occurrence of the B2↔B19' martensitic transition in the free state and under load. Based on physical and mechanical studies, the temperature ranges of the martensitic transformations (MT) in the free state and under load were established. Based on the thermodynamic description of the MT and the analysis of the characteristic temperatures of the MT, it was found that the MT mechanism is strongly dependent on the concentration of the alloying element.

The Effects of Trace H2S Levels on the Structure of Surface Scales in CO2 Corrosion

The CO2 corrosion of carbon steel is very strongly influenced by the formation of surface scales of corrosion products. Hence, the structure and composition of those scales has been the subject of much research. For oxygen-free brines in contact with gaseous CO2 at partial pressures up to ~50 bar, and temperatures up to ~120 °C, the formed scales are generally found to consist of a mixture of Fe3C (cementite) and FeCO3 (siderite). In simulated oil and gas production brines, the siderite incorporates Ca and Mg, while DeMarco et al [1] identified the scales that form over short times at ambient temperature as a mixture of Fe2(OH2)CO3 and Fe2O2CO3.Williams and colleagues [2-7] carried out detailed studies of the scales formed in solutions of moderate chloride content (0.5 – 1 M), saturated with CO2 at ~ 1 bar, pH adjusted to ~ 6.5 and at temperatures of ~ 80 °C. For the solutions containing only sodium chloride, siderite (FeCO3) was the major phase in the scale, though chukanovite (Fe2(OH)2CO3) was also present in some cases. With the addition of magnesium chloride, both siderite and chukanovite were always found in the scale, while there was no evidence of magnesium incorporation until the bulk concentration of MgCl2 was ~ 0.1 M. Considering the effect of low-level Cr and Mo alloying, it was found in the base sodium chloride solutions that mixed siderite/chukanovite scales were formed, but the scale became thinner and the chukanovite-to-siderite ratio decreased with alloy content. Even for alloys with 3.5 wt% Cr there was no evidence of discrete Cr (hydr)oxide layers within the scale. However, the addition of trace levels of H2S (∼ 0.5 μM) produced more significant changes. First, only chukanovite and FeS (mackinawite) were now found in the scale, with no siderite. Second, for the unalloyed steel and for alloys with 1 wt% Cr and up to 0.7% Mo, the scales were highly porous. Finally, for the 3.5wt% Cr alloy, a non-porous, protective layer was formed, about 200–600 nm thick.In this paper, we utilize ab-initio techniques to investigate the effects of very low level H2S on carbonate scale formation. In the past DFT has been used to understand the various aspects of corrosion and the design of corrosion inhibitors for various conditions [9-11]. We have used similar approach for studying the H2S adsorption on siderite and chukanovite surfaces, considering the experimental observation by Hassan et al [2], that trace amounts of H2S result in chukanovite over siderite. Initial studies show that there is a 0.7 eV higher interaction energy (more thermodynamically favorable) for H2S adsorption on chukanovite compared to siderite. This may imply the possibility that H2S could encourage chukanovite formation over siderite formation in aqueous environments.We further investigate this possibility using DFT to understand the mechanism that leads to formation of chukanovite. We aim to use implicit solvation in order to bring the effect of water in the vicinity. We further use the cluster approach within DFT, to explain the effect that alloying has on the scale formation. We take a bare Fe cluster and replace one of its atoms with an alloying element and study the electronic structure in the presence of H2S and CO2. The potential energy surface gets modified for a H2S—Fe interaction in the presence of Ni. We expect that this work would help us to have a deeper understanding of how alloying can impact or rather initiate certain kind of scale formation over others.

Abnormal evolution of resistivity and microstructure of annealed Ag nanoparticles/Ag–Mo films

Abstract Ag–Mo films with different thicknesses were prepared on polyimide substrate by magnetron sputtering and annealed at different temperatures. The effects of film thickness and annealing temperatures on the resistivity and microstructure of Ag–Mo alloys were investigated. Results show that many Ag nanoparticles were self-formed on Ag–Mo films’ surface. As the thickness of the Ag–Mo film increased from 163 to 409 nm, there was a significant decrease in its resistivity, dropping from 485.44 to 237.12 μΩ cm. Resistivity of the Ag–Mo film is dependent on the annealing temperature. When temperature rises from room temperature to 180℃, the resistivity decreases from 390.62 to 339.37 μΩ cm, with little change. After annealing above 270℃, a sudden increase of resistivity of the Ag–Mo film was attributed to the growth of Ag particles on the film surface contributing to the increase in surface roughness, which hindered electron transport and caused severe surface scattering. High-resistivity Ag–Mo films are expected to be candidates for high-resistivity thin-film devices.

The positive contribution of Cr2O3 reinforcing nanoparticles to enhanced corrosion and tribomechanical performance of Ni–Mo alloy layers electrodeposited from a citrate-sulfate bath

The service lifetime and efficiency of the engineering materials can be enhanced by adopting an appropriate surface modification strategy. This work has endeavored to finish the surface of St37 steel by electrodeposited Ni–Mo alloy layers strengthened by various levels of suspended Cr2O3 nanoparticles in the bath, i.e., 0–8 g/L, to obtain high corrosion and tribomechanical performance. The phase structure, morphology, chemistry, and roughness of the surfaces were assessed by XRD, FESEM, EDS, and AFM, respectively. Corrosion performance of the developed films was measured using OCP, EIS, and potentiodynamic polarization techniques, as well as long-term immersion in the corrosive NaCl medium. Vickers microhardness tester and ball-on-disk tribometer were employed to evaluate the tribomechanical behavior of the coatings. While there is no change in the phase structure of the Ni–Mo alloy layer with the included Cr2O3 nanoparticles, the nanocomposite layers show a more compact and rougher surface. The microhardness of the alloy coating was enhanced by approx. 30 % with the inclusion of the 8 g/L Cr2O3 nanoparticles in the electrolyte. An increase in polarization resistance of the nanocomposite layers compared to alloy one, by 16 kΩ, demonstrated the improvement in the corrosion protection performance with the included nanoparticles. The Ni–Mo–Cr2O3 nanocomposite layers offered lower COF and wear mass loss than the Ni–Mo alloy layer, irrespective of Cr2O3 loadings. The surface modification of mild steels by the Ni–Mo–Cr2O3 nanocomposite films can promote their service lifetime and efficiency in severe industrial applications.

Recovery of W–Mo Alloy Scrap and the Photochromic Properties of WO3/MoO3 Composite Products

Recovery of W–Mo Alloy Scrap and the Photochromic Properties of WO₃/MoO₃ Composite Products

Segregation behavior of alloying elements at the fcc-Fe/TiC interface by first principles exploration

In this paper, the effects of rare earth elements on the bonding strength and stability of TiC/fcc-Fe interface are explored by using the first-principles method based on density functional theory. The results show that the Ti terminal is more stable than the C terminal in the process of forming the interface. The alloying elements tend to segregate at position 2 on the side of fcc-Fe. The segregation of Mo, Nb, Cr and Ce alloying elements increases the interatomic electron cloud enrichment and consumption between the interfaces and enhances the Fe–Ti interactions. The d orbitals of Mo, Nb, Cr and Ce and f orbitals of Ce have strong hybridization with Fe-d orbitals and Ti-d orbitals electrons near the Fermi energy level, indicating an increase in bonding strength and stability of the interfaces. When Fe atoms are replaced by W, Ni and Al atoms, the covalent bond strength between interfacial atoms is reduced, thus weakening the interfacial bonding strength. This provides solid theoretical foundation with regard to further application in austenitic heat-resistant steel fields.

Comparing the Cold, Warm, and Hot Deformation Flow Behavior of Selective Laser‐Melted and Electron‐Beam‐Melted Ti–6Al–2Sn–4Zr–2Mo Alloy

The cold, warm, and hot deformation flow behavior and mechanical properties of the Ti‐6242 alloy produced by selective laser melting (SLM) and electron beam melting (EBM) are compared. Hot compression tests are conducted over a wide temperature range (100–1000 °C) at a constant strain rate of 0.001 s−1. The yield and overall strength levels of the SLMed specimens are higher than those of the EBMed specimens at all temperatures. A thermally stable region is observed for SLMed specimens in the temperature range of 100–700 °C, but the strength level drops significantly (approximately 300–500 MPa) at above 700 °C. The stability region shifts to the lower temperature range of 100–600°Cfor the EBMed specimens, and strength starts to decrease at 600 °C. Both specimens experience fracture in a cold‐temperature regime but exhibit a high strain tolerance of approximately 0.4. The SLMed samples display a completely brittle behavior at a warm temperature regime, whereas, the EBMed specimens demonstrate better formability, tolerating higher compressive strains. The softening fraction substantially increases at high temperatures, indicating safe domains for thermomechanical processing of additively manufactured Ti6242 alloy.