Diffusion Annealing Research Articles

Research Status of Large‐Size Carbides in High‐Carbon Chromium Bearing Steel

Metallurgical quality of bearing steel is an important foundation and guarantees for determining the performance, accuracy, service life, and reliability of bearings. Nowadays, advances in refining technology have led to a significant increase in the cleanliness of bearing steel, and the control of large‐size carbides (primary, banded, and network carbides) has become particularly important. In this article, the recent research on large‐size carbides regarding morphology, precipitation mechanism, and control methods is reviewed. Firstly, the morphological characteristics of carbides are summarized. Primary carbides appear as blocky, lamellar, or irregular shapes, while banded carbides are distributed in bands. Network carbides mainly precipitate along the austenitic grain boundaries and aggregate to form networks. Secondly, the precipitation mechanisms of carbides are summarized. Dendritic segregation is the fundamental cause of the formation of primary and banded carbides, whereas network carbides are the supersaturation precipitation of carbon at austenite grain boundaries. Finally, methods for controlling large‐size carbides are summarized, including improving dendritic segregation, high‐temperature diffusion annealing, improving rolling and cooling processes and using magnesium or rare‐earth treatments. No single method offers sufficient carbide control, and mechanism of rare‐earth refining carbides is unknown. Thus, a comprehensive approach should be used in production to effectively regulate carbides in steel.

Effect of Diffusion Annealing and Aging Post-Treatments on Scratch Properties of Boride Layers on CoCrMo Alloy

Effect of Diffusion Annealing and Aging Post-Treatments on Scratch Properties of Boride Layers on CoCrMo Alloy

Microstructural and mechanical characterization of chromium carbide layers obtained on 100Cr6 and X200Cr12 steels by conversion

Carbides and Nitrides of transition metals are widely used due to their interesting properties. Several deposition methods and techniques can be used to produce carbide and nitride coatings. The choice of how to make the deposit depends on several parameters such as, the conditions of use of these deposits, the thickness to be produced, the adhesion between the substrate the deposit, and the cost. In this work, hard coatings of chromium carbide were produced by a conversion treatment on 100Cr6 and X200Cr12 steels. The conversion treatment consists of electrode position of chromium on the surface of 100Cr6 and X200Cr12 steels followed by diffusion annealing treatment at 1000 and 1100 °C for holding times of 1 and 2 hours. The obtained results show that, for all the conversion treatments carried out in this work, there was formation of chromium carbides layer on the surface of steel. However, it should be noted that the nature of the constituting phases of the formed layer depends on the temperature of the diffusion annealing treatment and the duration at this temperature. It should also be noted that the X-ray diffraction analysis has allowed us to show the existence of chromium oxide in addition to chromium carbides. The microhardness profile and the scratch test show that the X200Cr12 steel sample shows better results.These properties are usually obtained by expensive methods such as PVD, CVD, while we can obtain them by easy and inexpensive methods.

In-situ synthesizing Al–Y precipitates in Mg–3Y/Al composites for enhancing high-temperature tensile properties

Mg–3Y/Al composites were produced through accumulated rolling bonding. During annealing, Al–Y precipitates were synthesized in-situ within the Mg–3Y/Al composites through solid diffusion reactions. In these composites, the volume fraction of the interface layer containing abundant Al–Y precipitates can reach approximately 74% after three passes of accumulated rolling bonding and diffusion annealing. At room temperature, the Mg–3Y/Al composite exhibits increased strength (∼273.9 MPa) but reduced ductility (∼3.5%) compared to the base Mg–3Y alloy (∼191.0 MPa, ∼30%), due to the presence of numerous Al–Y precipitates and residual dislocations. These Al–Y precipitates display remarkable thermal stability, maintaining their size without significant coarsening even after annealing at 400 °C for 1–4 h, thereby contributing to the exceptional thermal stability observed in Mg–3Y/Al samples. After annealing at 400 °C for 4 h, the tensile strength of the Mg–3Y/Al samples remained unchanged, while the ductility increased to 8.5%. At 300 °C, the Mg–3Y/Al composite demonstrates exceptional high-temperature strength (179.9 MPa), significantly surpassing that of the original Mg–3Y alloy (110.6 MPa). Moreover, compared to the original Mg–3Y alloy and magnesium alloys reported in the literature, the Mg–3Y/Al composite exhibits a higher RE-equivalent strength at 300 °C. This enhanced strength is primarily attributed to precipitation strengthening induced by fine Al–Y precipitates. These findings underscore that introducing fine Al–Y precipitates through a solid diffusion reaction is an effective approach for achieving outstanding high-temperature strength in magnesium alloys.

Bio-tribocorrosion resistance of CoB–Co2B and Co2B layers on CoCrMo alloy

Cobalt-based alloys, such as cobalt-chromium-molybdenum (CoCrMo), are known for their high mechanical strength and find extensive applications in the biomedical field such as manufacturing of tools, dental components, and orthopedic implants. The longevity of the CoCrMo alloy in service is intricately linked to its resistance to corrosion and wear. Specifically, tribocorrosion can contribute to material loosening; therefore, it is essential to explore surface treatments for cobalt-based alloys as a means to enhance their wear resistance, ensuring the prolonged durability of the material. This study provides novel insights into the bio-tribocorrosion resistance of the borided CoCrMo alloy when immersed in calf serum, emulating the synovial fluid. Two distinct microstructures of boride layers were examined in this research: (1) a CoB–Co2B layer formed through powder-pack boriding and (2) the borided surface underwent diffusion annealing to completely dissolve the CoB, resulting in a monophasic layer (Co2B). Following the ASTM G119-09 procedure, the total material loss (T), encompassing both material loss due to wear (WC) and corrosion (CW), was determined using a linear reciprocating ball-on-flat tribometer equipped with an electrochemical cell. Test results indicated that the presence of CoB–Co2B and Co2B layers on the CoCrMo alloy increased bio-tribocorrosion resistance approximately 2.4 times and 1.3 times, respectively, compared to the non-treated CoCrMo alloy. A dominant wear regime was observed for the borided surface exposed to diffusion annealing and the non-treated CoCrMo alloy, whereas the borided CoCrMo alloy exhibited a corrosion-wear regime. Clearly, these findings highlight the capability of the cobalt boride layer to improve the performance and extend the service life of the CoCrMo alloy in biomedical applications.

Thermodynamic modelling application for prediction of diffusion formation of supersaturation solution

Abstract In this paper the effect of diffusion formation of supersaturated solid solution in the Al–Ge system is discussed. It was shown that at relatively low temperatures of diffusion annealing, Ge concentration in Al-based solid solution became higher than the solubility limit at given temperatures. The maximal concentration of Ge was determined by extrapolation of the diffusion profile on the Ge/Al interface. Analysis of diffusivity of Al in Ge allowed to suggest that slow diffusion in Ge restricts the formation of Ge-based solid solution. Qualitative approach confirmed this suggestion.

Microstructural characterization of 15Cr steel after quenching and slow cooling rates

Abstract Ferritic 15 %-Cr steels have better oxidation resistance, due to their higher chromium content, and creep strength, their lower dislocation density and lack of lath microstructure than conventional martensitic steels such as MarBN. Their mechanical properties are sensitive to chemical composition and heat treatment. In this study, we first simulated the formation of stable phases in two ferritic steels containing 2 % nickel (wt.%) and an alloy without nickel using the thermomechanical software MATCALC. Microstructural analysis using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) reveals the formation of carbides and intermetallic phases after diffusion annealing, both during rapid cooling in oil and slow cooling in the furnace. Dilatometry and XRD studies confirm the gradual phase transformation of ferrite to austenite from 650 °C onwards during heating. Dilatometry also shows that ferritic steels have a lower coefficient of thermal expansion than martensitic steels, austenitic steels, and superalloys, which results in lower thermal stresses during frequent start-up and shutdown of power plants.

Hot-Dip Aluminizing of Flow-formed AISI 4140 Steel

Cold plastic deformations recognizably cause increasing lattice imperfections such as point defects and dislocations in the structure, which could then have an effect on diffusion characteristics of the material. In order to explore such an effect of flow forming, a flow formed AISI 4140 steel and an annealed 4140 steel were subjected to the HDA process in a molten Al7020 bath at 750◦C for 4 min, and a subsequent diffusion annealing was performed at 800◦C, and their coating characteristics such as coating thickness and hardness were compared. The results indicated that the coating thickness of the flow formed samples was higher (80◦m) than that of the annealed sample (50◦m) after the HDA process. Diffusion annealing increased the coating thickness of both samples five times, reaching 400◦m and 250◦m for the flow formed and the annealed samples, respectively. Comparing the measured thickness of the coatings revealed that flow forming accelerates diffusion during the HDA process, probably due to the defect structure induced by the flow forming. On the other hand, the coating hardness was in between 1000-1100 HV for both samples, implying that the initial condition of the sample does not have a remarkable effect on hardness after the HDA process.

Features of formation of titanium–nickel system coatings during annealing of titanium with nickel layer

The results of studies of the processes of formation of coatings based on titanium nickelides during diffusion annealing of titanium at a temperature of 750...850 °C with a chemical nickel coating are presented. The kinetics of transformation of a nickel layer on titanium into an intermetallic coating based on titanium nickelides is shown. The dependence of the chemical composition of the formed layers of nickelides on the temperature-time regimes of annealing has been established.

Fabrication of AZ31/Mg3Y Composites with Excellent Strength and Plasticity via Accumulated Rolling Bonding and Diffusion Annealing

Fabrication of AZ31/Mg3Y Composites with Excellent Strength and Plasticity via Accumulated Rolling Bonding and Diffusion Annealing

Mechanical properties and fracture behavior in copper-brass heterostructured fibers

Inspired by natural structures like bamboo and bone, the incorporation of heterogeneous fibrous structure plays a significant role in skillfully optimizing their mechanical properties. A set of copper-brass heterostructured fibers has been successfully designed and fabricated by a novel strategy, named DRA (diffusion welding, rotary swaging and annealing). This leads to a significant improvement in the synergy between strength and ductility, which can be attributed to the HDI (hetero-deformation induced) hardening effect caused by the high density of hetero-interfaces. The experimental results found that once the GND (geometrically necessary dislocations) density around the hetero-interface reaches the saturation, some GNDs can spread into the adjacent copper and brass zones to alleviate partial stress concentration. The presence of four-sides interfaces in the fibrous composite restricts the dislocation storage capacity of individual fiber, thereby abundant GNDs accumulating near the hetero-interface to produce significant stress concentration and HDI stress. Simultaneously, the severe stress concentration promotes the initiation and propagation of micro-cracks at the hetero-interfaces. These results lead to a more significant HDI hardening while a faster decrease in the work hardening rate of the hetero-fiber during the later stage of tension. Our findings have significantly enhanced our understanding of the deformation mechanism of heterostructured materials. Additionally, this innovative structural design strategy has proven to be highly valuable in the development of heterostructured materials with substantial potential for various applications.

Effect of yttrium on the formation, microstructure and high-temperature oxidation resistance of the oxide film on the surface of FeCr alloy

Yttrium was diffused into the surface layer of FeCr alloy using an electrodeposition–thermal method via yttrium nitrate solution and diffusion annealing at 1000 °C. Y-doped FeCr samples exhibited excellent high-temperature oxidation resistance. The mass gains and spallation of Y-doped FeCr samples were only 0.51–0.64 mg/cm2 and 0.19–0.25 mg/cm2, respectively, and much lower than the alloy without yttrium (20.7 mg/cm2 and 9.08 mg/cm2, respectively) when oxidized in air at 900 °C for 200 h. The presence of yttrium increased the number of oxide nucleation sites, led to the transformation of the oxide from the Cr2O3 phase to the spinel (FeCrY)3O4 phase and accelerated the rapid formation of a continuous oxide film in the initial oxidation stage. The yttrium content affected the formation and microstructure of oxide film due to the lattice distortion of the FeCr phase. Excess Y induced formation of Y2O3 at grain boundaries, which further increased the bonding force between the oxide film and the substrate. A first-principles calculation confirmed that the bond strength between Y and other atoms was improved significantly. The length of the CrY bond showed little change under an external stress, which increased the bonding strength of the FeCr/Cr2O3 interface.

Generative adversarial networks via a composite annealing of noise and diffusion

Generative adversarial network (GAN) is a framework for generating fake data using a set of real examples. However, GAN is unstable in the training stage. In order to stabilize GANs, the noise injection has been used to enlarge the overlap of the real and fake distributions at the cost of increasing variance. The diffusion process (or data smoothing in its spatial domain) removes fine details in order to capture the structure and important patterns in data but it suppresses the capability of GANs to learn high-frequency information in the training procedure. Based on these observations, we propose a data representation for the GAN training, called noisy scale-space (NSS), that recursively applies the smoothing with a balanced noise to data in order to replace the high-frequency information by random data, leading to a coarse-to-fine training of GANs. We experiment with NSS using DCGAN and StyleGAN2 based on benchmark datasets in which the NSS-based GANs outperforms the state-of-the-arts in most cases.

ОБ ИДЕНТИФИКАЦИИ ПРОСЛОЙКИ TIC В СОСТАВЕ ДИФФУЗИОННОЙ ЗОНЫ СМИК СИСТЕМЫ TI-FE

The paper presents the data of electron-optical studies on the identification of the TiC interlayer in the composition of the diffusion zone, which is formed at the interlayer boundary in the SMIC of the Ti - Fe system after diffusion annealing.

ОЦЕНКА ЭНЕРГЕТИЧЕСКИХ ЗАТРАТ ПРИ ДИФФУЗИОННОМ ОТЖИГЕ СВАРЕННОГО ВЗРЫВОМ БИМЕТАЛЛА ВТ1-0 + М1

A technique is presented that makes it possible to optimize the process of diffusion annealing of an explosion-welded titanium-copper bimetal, taking into account the heat costs for the formation of coatings based on titanium cuprides and losses for heating the furnace, holding at a given temperature, loading and unloading workpieces.

Magnetic Properties of Silicon with Paramagnetic Impurity Atoms

One of the possible ways to obtain silicon with magnetic properties is the introduction of paramagnetic impurities into silicon: Cr, Mn, Fe, Ni, and Co. In our opinion, silicon materials containing magnetic nanosized clusters are most suitable for spintronic devices. The possibility of obtaining silicon with magnetic properties by diffusion doping was studied in this work. To obtain silicon doped with Cr, Mn, Fe and Ni impurity atoms, p-type single-crystal silicon with a specific resistance of ρ = 5 Ohm·cm and ρ = 0.5 Ohm·cm was used, and for doping with Co atoms, n-type silicon with resistivity ρ=10 Ohm·cm was used. The diffusion temperature and time were chosen such that, after diffusion annealing, the samples with impurity Cr, Fe, and Mn atoms remained highly compensated p-type, and when doped with impurity Co atoms, they remained high-resistance n-type. The results of the study showed that with decreasing temperature, the value of the negative magnetoresistance Δρ/ρ in the Si<Mn> samples increases and reaches its maximum value (about 800%) at T = 240 K, a further decrease in temperature leads to a decrease in the magnetoresistance, and at a temperature T = 170 K, the sign of the magnetoresistance is inverted. In Si <Cr> samples, with decreasing temperature, the positive magnetoresistance turns into a negative one, the value of which increases with decreasing temperature, and is achieved at T=100 K Δρ/ρ = 45–50%. In Si<Fe> samples, with decreasing temperature, the value of negative magnetoresistance increases monotonically and at T=100 K its value is Δρ/ρ = (100÷120) %. The study in Si<Сo> samples showed that with decreasing temperature the value of positive magnetoresistance increases and at Т=100 K it reaches Δρ/ρ = (17÷20) %. The study of magnetoresistance in samples - Si<Ni> showed that with decreasing temperature the value of positive magnetoresistance increases and at T=100 K it reaches Δρ/ρ = (10÷15) %. When studying the magnetic properties of p-Si <B, Mn> samples at low temperatures (below T=30 K), a ferromagnetic state was found, i.e. succeeded in obtaining a magnetic semiconductor material by the method of diffusion of a paramagnetic impurity. In the overcompensated Si <B, Mn> (n‑type) samples, no magnetic hysteresis was found. This shows a significant effect on the magnetic properties of the manganese impurity in silicon of its charge and, accordingly, spin state. Based on the results obtained, it can be argued that diffusion doping of silicon with manganese can be used to obtain silicon with magnetic properties.

Hot Deformation Behavior of 301L Stainless Steel and Dissolution Behavior of δ‐Ferrite During Heat Treatment

The hot deformation behavior of 301 L stainless steel is investigated at 1000–1250 °C and 0.1–50 s−1. Deformation characteristics are studied through compressive stress–strain curves and constitutive equations. According to the dynamic material model and a series of diffusion annealing experiments, the hot processing map of 301 L stainless steel is established to determine the suitable processing domain. The results show that the stable domain is located in 1085–1240 °C and high strain rate range of 4.5–50 s−1, and the strain rate is the main factor affecting the machinability. Based on the hot compression tests, δ‐ferrite gradually forms a network structure with the increase of temperature; however, it can be inhibited at high strain rate. Therefore, it is necessary to reduce the temperature and increase the strain rate in the actual processing of the machinable area. It is found that diffusion annealing can reduce the content of δ‐ferrite from 12% to 0.67%, and the dissolution of δ‐ferrite is controlled by the diffusion of Cr and Ni, especially noticeable at the interface between γ and δ phase. Finally, the optimum diffusion annealing process parameter is determined at 1300 °C and 10 min.

Growth behavior of intermetallic layers at the interface between Cu and eutectic Sn–Bi by grain boundary diffusion with the grain growth at solid-state temperatures

The growth kinetics and rate-controlling processes of intermetallic layers formed in Cu/(Sn-58 wt% Bi) diffusion couples were investigated. Isothermal annealing of diffusion couples was conducted in the temperature range of 363–393 K for various times up to 384 h. In the diffusion couple, an intermetallic layer composed of Cu6Sn5 with irregular scallop shapes and Cu3Sn with relatively uniform thickness forms at the Cu/(Sn–Bi) interface. Isothermal sections of the equilibrium phase diagram in the ternary Bi–Cu–Sn system were calculated at the isothermal annealing temperatures and the peak temperature of the reflow process by a CALPHAD (calculation of phase diagrams) method. The diffusion path passes through the three-phase tie-triangle, including Cu6Sn5 and Cu3Sn. The obtained thicknesses were plotted against the annealing time, and a power function equation was found to describe their relationship. The values of the exponent in the power function were close to 0.25, indicating that the layer growth was predominantly controlled by boundary diffusion with the grain growth. Furthermore, the exponent values were relatively insensitive to the annealing temperature. The relationship between the exponent and the annealing temperature was analyzed, and it was concluded that the grain growth in the intermetallic layer followed a parabolic law. The growth and morphology evolution of the intermetallic compound and Sn–Bi eutectic microstructure at the interface were depicted, shedding light on the widening of the eutectic microstructure. Additionally, the activation enthalpy for the rate-controlling process of intermetallic layer growth at solid-state temperatures was evaluated using a least-squares method, providing insights into the energy barrier for the diffusion or transport of atoms across the interface. This study contributes to a better understanding of intermetallic layer formation and growth in Cu/(eutectic Sn–Bi) diffusion couples, offering valuable information for developing reliable solder joints and high-temperature solders.

Microstructure, magnetocaloric and mechanical properties of LaFe11.8Si1.2/Y64Co36 composites prepared by hot pressing and diffusion annealing

Microstructure, magnetocaloric and mechanical properties of LaFe11.8Si1.2/Y64Co36 composites prepared by hot pressing and diffusion annealing

Superior comprehensive properties of LaFe11.8Si1.2/Ce60Co40 magnetocaloric composites

LaFe11.8Si1.2/10 wt%Ce60Co40 composites were prepared by spark plasma sintering and subsequent diffusion annealing. A novel core–shell structure is observed with the LaFe11.8Si1.2 particles as the core and the (La,Ce)2(Fe,Co,Si)17 (2:17) phase as the shell. As diffusion annealing time (ta) increases, this core–shell structure is replaced by the formation of the (La,Ce)1(Fe,Co,Si)13 phase. Annealing at 1323 K for 12 h results in samples with (−ΔSM)max of 9.30 J/(kg·K) (Δμ0H = 2 T), good mechanical properties ((σbc)max = 402 MPa, ε = 4.21%) and thermal conductivity of 8.7 W/(m·K). Thus, bulk composites with excellent comprehensive properties for magnetic refrigeration are obtained in this work.