Gas Quenching Research Articles

Stabilizing Solution–Substrate Interaction of Perovskite Ink on PEDOT:PSS for Scalable Blade Coated Narrow Bandgap Perovskite Solar Modules by Gas Quenching

The development of scalable 1.25 eV mixed Pb–Sn perovskite solar modules by blade coating lags behind Pb‐based perovskites due to limited understanding of solution–substrate interaction of the perovskite ink on PEDOT:PSS and subsequent gas quenching. To address this challenge, the wet film deposition and quenching process to better understand narrow bandgap perovskite film formation on PEDOT:PSS are studied. It is found that the wetting of Pb–Sn perovskite ink on PEDOT:PSS is highly unstable over relevant coating time scales, causing the contact angles to decrease rapidly from 42° to 16° within seconds. This instability leads to localized irregularities in the wet film, resulting in uneven solvent extraction and inhomogeneous nuclei density. As a result, rough perovskite films with voids at the buried interface are obtained. To overcome this problem, a quasistatic wetting process by reducing the blade coating speed is developed, thereby stabilizing the wetting behavior of Pb–Sn perovskite precursor ink on PEDOT:PSS. This optimized process facilitates the deposition of high‐quality, void‐free Pb–Sn perovskite films with uniform thickness over 8 cm of coating length using moderate (1.4 bar) N2 quenching. 20% efficient narrow bandgap perovskite solar cells and minimodules with 15.8% active area efficiency on 15.9 cm2 are achieved.

Artificial Intelligence Modeling of the Heterogeneous Gas Quenching Process for Steel Batches Based on Numerical Simulations and Experiments

High-pressure gas quenching is widely used in the metals industry during the heat treatment processing of steel specimens to improve their material properties. In a gas quenching process, a preheated austenised metal specimen is rapidly cooled with a gas such as nitrogen, helium, etc. The resulting microstructure relies on the temporal and spatial thermal history during the quenching. As a result, the corresponding material properties such as hardness are achieved. Challenges reside with the selection of the proper process parameters. This research focuses on the heat treatment of steel sample batches. The gas quenching process is fundamentally investigated in experiments and numerical simulations. Experiments are carried out to determine the heat transfer coefficient and the cooling curves as well as the local flow fields. Quenched samples are analyzed to derive the material hardness. CFD and FEM models numerically determine the conjugate heat transfer, flow behavior, cooling curve, and material hardness. In a novel approach, the experimental and simulation results are adopted to train artificial neural networks (ANNs), which allow us to predict the required process parameters for a targeted material property. The steels 42CrMo4 (1.7225) and 100Cr6 (1.3505) are investigated, nitrogen is the quenching gas, and geometries such as a disc, disc with a hole and ring are considered for batch series production.

Ultrasonic‐Assisted Processing Combined with Gas Quenching for Fabricating High‐Performance and Stable Inverted Perovskite Solar Cells

AbstractIn recent years, perovskite solar cells have attained unprecedented advancements in power conversion efficiency, yet their commercialization remains a formidable challenge. Addressing this challenge relies on developing an affordable and scalable method for manufacturing top‐notch perovskite films. This study presents an innovative strategy, employing both gas quenching technology and ultrasonic‐assisted processing (UAP), to fabricate high‐caliber perovskite thin films. The UAP process enhances the grain size of the perovskite film, reduces grain boundary defects, improves carrier extraction and transport, and suppresses carrier nonradiative recombination. Furthermore, it effectively reduces residual stress and mitigates lattice distortion in the perovskite crystals. Ultimately, efficient and stable inverted perovskite solar cells using FA0.87Cs0.13PbI2.7Br0.3 and FA0.85MA0.1Cs0.05PbI3 perovskite are successfully prepared. The target device achieved a power conversion efficiency of 22.32% and 24.51%, respectively. Moreover, the target devices exhibited enhanced photostability. This work provides a cost‐effective and scalable method for producing high‐quality perovskite films, paving the way for the commercialization of perovskite solar cells.

Nitrogen Gas Quenching Pressure Effect on Bs S155 Alloy Steel in Vacuum Furnace

Nitrogen Gas Quenching Pressure Effect on Bs S155 Alloy Steel in Vacuum Furnace

Development and Prospect of Vacuum High-Pressure Gas Quenching Technology

As industrial modernization surges forward, the heat treatment industry strives for lower pollution, reduced oxidation and defects, minimized waste, and automatization. This paper reviews the mechanisms, processes, equipment, and simulations of the vacuum gas quenching technology, presenting a comprehensive account of the structure and working principle of a typical vacuum gas quenching furnace. Firstly, the mechanism of the heat transfer process, flow process, and flow–heat transfer–phase transition coupling were summarized. Then, the influences of process parameters on the mechanical properties and distortion of vacuum gas quenched workpieces, as well as the process optimization methods, were discussed. Finally, the advantages of vacuum gas quenching in energy saving, low pollution, and high efficiency were introduced, with the future development directions figured out.

Controlling Thin Film Morphology Formation during Gas Quenching of Slot-Die Coated Perovskite Solar Modules.

Transferring record power conversion efficiency (PCE) >25% of spin coated perovskite solar cells (PSCs) from the laboratory scale to large-area photovoltaic modules requires significant advances in scalable fabrication techniques. In this work, we demonstrate the fundamental interrelation between drying dynamics of slot-die coated precursor solution thin films and the quality of resulting slot-die coated gas-quenched polycrystalline perovskite thin films. Well-defined drying conditions are established using a temperature-stabilized, movable table and a flow-controlled, oblique impinging slot nozzle purged with nitrogen. The accurately deposited solution thin film on the substrate is recorded by a tilted CCD camera, allowing for in situ monitoring of the perovskite thin film formation. With the tracking of crystallization dynamics during the drying process, we identify the critical process parameters needed for the design of optimal drying and gas quenching systems. In addition, defining different drying regimes, we derive practical slot jet adjustments preventing gas backflow and demonstrate large-area, homogeneous, and pinhole-free slot-die coated perovskite thin films that result in solar cells with PCEs of up to 18.6%. Our study reveals key interrelations of process parameters, e.g., the gas flow and drying velocity, and the exact crystallization position with the morphology formation of fabricated thin films, resulting in a homogeneous performance of corresponding 50 × 50 mm2 solar minimodules (17.2%) with only minimal upscaling loss. In addition, we validate a previously developed model on the drying dynamics of perovskite thin films on small-area slot-die coated areas of ≥100 cm2. The study provides methodical guidelines for the design of future slot-die coating setups and establishes a step forward to a successful transfer of solution processes towards industrial-scale deposition systems beyond brute force optimization.

Combined CFD and Heat Treatment Simulation of High-Pressure Gas Quenching Process

Abstract To improve the process development for high pressure gas quenching a digital quenching simulation model combining the fields of computational fluid dynamics and heat treatment process simulation has been developed. It was found that the gas flow and hence the quenching properties depend on both local (geometry of parts, carrier and chamber) as well as global influencing factors (fan characteristics, system pressure and hydraulic resistances). Therefore, a computational fluid dynamics model that includes all these factors was realized. The approach includes a heat transfer analysis to determine the local heat exchange coefficients on a component level. By connecting the computational fluid dynamics model and heat treatment simulation the local quenching characteristics are used to compute the temperature history of the quenched part. Based on a thermo-metallurgical heat treatment simulation the computed local cooling curves and metallurgical phase compositions are used to accurately predict the part properties like microstructure and hardness. The applicability of the model has been confirmed by hardness measurements. Hardness results for different batch positions, batch setups or tray systems can now be computed enabling an efficient virtual development of the gas quenching process.

Numerical Simulation of the Slag Granulation Process in Gas Quenching Under Multi-influencing Factors

Numerical Simulation of the Slag Granulation Process in Gas Quenching Under Multi-influencing Factors

Numerical Simulation of Low-Pressure Carburizing and Gas Quenching for Pyrowear 53 Steel

The hardness and phase composition are, among other things, the critical material properties considered in the quality control of aerospace gears made from Pyrowear 53 steel after high-pressure gas quenching. The low availability of data on and applications of such demanding structures justify investigating the choice of the material and the need to improve its manufacturability. In this study, computational finite-element analyses of low-pressure carburizing followed by oil and gas quenching of Pyrowear 53 steel were undertaken, the objective of which was to examine the influence of the process parameters on the materials’ final phase composition and hardness. The material input was prepared using JMatPro. The properties computed by the CALPHAD method were calibrated by the values obtained from physical experiments. The heat transfer coefficient was regarded as an objective variable to be optimized. A 3D model of the Standard Navy C-ring specimen was utilized to predict the phase composition after the high-pressure gas quenching of the steel and the hardness at the final stage. These two parameters are considered good indicators of the actual process parameters and are used in the industry. The results of the simulation, e.g., optimized heat transfer coefficients, cooling curves, and hardness and phase composition, are presented and compared with experimental values. The accuracy of the simulation was validated, and a good correlation of the data was found, which demonstrates the quality of the input data and setup of the numerical procedure. A computational approach to heat treatment processes’ design could contribute to accelerating new procedures’ implementation and lowering the development costs.

Impact of Cooling Rate during High-Pressure Gas Quenching on Fatigue Performance of Low Pressure Carburized Gears

The impact of cooling rate during high-pressure gas quenching on the fatigue performance of low-pressure carburized spur gears was studied for steel grades 20MnCr5 and 17NiCrMo6-4. The results show an increased fatigue limit by 10 to 11% when applying a slower cooling rate for both steel grades. Moreover, for 20MnCr5 the slower cooled gears show an increase in compressive residual stresses by 130 MPa compared to the faster cooling, although no significant difference was observed for 17NiCrMo6-4. It is also seen that the cooling rate affects the core hardness for both steel grades, while other properties like surface hardness, case-hardness depth and martensite variant pairing were unaffected. The results for the retained austenite content and average martensite unit size show no clear effect of the cooling rate. The possible influence of different carbon distributions after quenching for the two used cooling rates on the carbide precipitation and fatigue limit is discussed.

Estimation and analysis of surface heat flux during gas quenching through IHC method

Gas Quenching is a process of quenching steel components with a gas quenchant. This process, due to its several advantages is being extensively used now a days. This work studies the effect of the variation of gas jet pressure and the standoff distance (SOD), which is the distance between the quench probe and the tip of the nozzle on the quenching heat transfer during gas quenching. A gas quenching chamber of octagonal cross-section of side 100 mm was used for quenching experiments, in which an array of nozzles was fixed. The cylindrical workpieces of 20 mm diameter and 50 mm length were machined from stainless steel 304L and K-type thermocouples were fixed at the selected locations inside the workpiece to read the temperature during quenching. Compressed air as the quenchant at different pressures of 4 bar, 6 bar and 8 bar and different SOD of 9 cm, 10 cm and 11 cm were used to study the effect of these two parameters on the quenching heat transfer rates. Surface heat flux computations were made using Inverse Heat Conduction (IHC) method using the measured time–temperature data as input. It was found out that as the pressure increased, the cooling rate and the peak surface heat flux increased and as the nozzle standoff distance was increased, the cooling rate and the peak surface heat flux dropped. The effect of increasing the nozzle SOD by 1 cm was more than the reduction of gas jet pressure by 2 bar.

Minimizing Distortion During High-Pressure Gas Quenching, Part II

Abstract The second article in this series looks at materials testing, microstructural evaluation, mechanical testing, and residual stress and distortion using the DANTE Controlled Gas Quenching process.

Minimizing Distortion During High-Pressure Gas Quenching, Part I

Abstract A new method to control distortion in difficult-to-quench geometries addresses the nonuniform cooling inherent in most gas quenching processes. This article describes the development of a controlled gas quenching prototype unit design and its operation. The prototype unit constructed was able to achieve great control within the temperature range of 400 to 100°C, using varying rates of temperature change.

Microstructure and Material Properties of Ti-15mass%Nb Alloy after Gas Nitriding and Quenching Process

The α′ martensite of Ti-15mass%Nb alloy exhibits high internal friction with high damping properties. However, its structure is smoother than the α + β structure. Therefore, a hardened surface layer is required for abrasion resistance. This study fabricated a martensite structure inside the nitriding layer by quenching, after gas nitriding at 1023 and 1223 K. Vickers hardness test, X-ray diffraction, scanning electron microscopy (SEM), and SEM-energy dispersive X-ray (SEM-EDX) measurements from the surface to the inside were made after the heat treatment process. In addition, the Young’s modulus and internal friction were calculated from the damping analysis. The α-TiN0.3 and β phase region was formed at approximately 80 µm from the surface at 1023 and 1223 K, and it was hardened. The internal friction of the gas nitriding and quenching specimens at 1023 and 1223 K was relatively high, though it did not reach that of the as-quenched specimen owing to the influence of the surface structure. From these results, it is considered that these material property values of the alloy can be controlled using the nitriding and quenching processes.

Revealing the Perovskite Film Formation Using the Gas Quenching Method by In Situ GIWAXS: Morphology, Properties, and Device Performance

AbstractThe optoelectronic properties, morphology, and consequently the performance of metal halide perovskite solar cells are directly related to the crystalline phases and intermediates formed during film preparation. The gas quenching method is compatible with large‐area deposition, but an understanding of how this method influences these properties and performance is scarce in the literature. Here, in situ grazing incidence wide angle X‐ray scattering is employed during spin coating deposition to gain insights on the formation of MAPbI3 and CsxFA1−xPb(I0.83Br0.17)3 perovskites, comparing the use of dimethyl sulfoxide (DMSO) and 2‐methyl‐n‐pyrrolidone (NMP) as coordinative solvents. Intermediates formed using DMSO depend on the perovskite composition (e.g., Cs content), while for NMP the same intermediate [PbI2(NMP)] is formed independently on the composition. For MAPbI3 and CsxFA1−xPb(I0.83Br0.17)3 with a small amount of Cs (10% and 20%), the best efficiencies are achieved using NMP, while the use of DMSO is preferred for higher (30% and 40%) amount of Cs. The inhibition of the 2H/4H hexagonal phase when using NMP is crucial for the final performance. These findings provide a deep understanding about the formation mechanism in multication perovskites and assist the community to choose the best solvent for the desired perovskite composition aiming to perovskite‐on‐silicon tandem solar cells.

Study on the Process of Vacuum Low Pressure Carburizing and High Pressure Gas Quenching for Carburizing Steels

The vacuum low pressure carburizing and high pressure gas quenching processes of 20CrMo, 20CrMnTi and 20Cr2Ni4 with acetylene as carburizing medium were investigated. The results show that the carburizing and diffusion time significantly affected the carburizing performance. Carburized with the process of C2H2 flow rate 10L/min, N2 flow rate 10L/min, carburizing pressure 3kPa, carburizing time 42min, diffusion time 140min and gas quenching pressure 1.5MPa, 20CrMo, 20CrMnTi and 20Cr2Ni4 can obtain the surface carbon content of 0.74%-0.78% and carburizing depth of 0.81mm-0.83mm. Meanwhile, the microstructure showed first grade carbide, and there was no internal oxidation laye on the surface. The carburizing constant and the diffusion time to carburizing time ratio were modified to be more suitable for the carburizing process.

Algorithm Scheme to Simulate the Distortions during Gas Quenching in a Single-Piece Flow Technology

Low-pressure carburizing followed by high-pressure quenching in single-piece flow technology has shown good results in avoiding distortions. For better control of specimen quality in these processes, developing numerical simulations can be beneficial. However, there is no commercial software able to simulate distortion formation during gas quenching that considers the complex fluid flow field and heat transfer coefficient as a function of space and time. For this reason, this paper proposes an algorithm scheme that aims for more refined results. Based on the physical phenomena involved, a numerical scheme was divided into five modules: diffusion module, fluid module, thermal module, phase transformation module, and mechanical module. In order to validate the simulation, the results were compared with the experimental data. The outcomes showed that the average difference between the numerical and experimental data for distortions was 1.7% for the outer diameter and 12% for the inner diameter of the steel element. Numerical simulation also showed the differences between deformations in the inner and outer diameters as they appear in the experimental data. Therefore, a numerical model capable of simulating distortions in the steel elements during high-pressure gas quenching after low-pressure carburizing using a single-piece flow technology was obtained, whereupon the complex fluid flow and variation of the heat transfer coefficient was considered.

Determination of Cooling Intensity Using Transient Heat Transfer Technique at Gas Quenching in Vacuum Heat Treating Furnace

Determination of Cooling Intensity Using Transient Heat Transfer Technique at Gas Quenching in Vacuum Heat Treating Furnace

Granulation Effect Analysis of Gas Quenching Blast Furnace Slag with Different Basicities

High content amorphous phase blast furnace slag beads were prepared by gas quenching blast furnace slag (BFS), which could not only avoid a series of environmental problems caused by traditional water quenching methods, but also significantly increase the added value of BFS subsequent products. In this paper, the granulation mechanism of BFS and the amorphous phase formation mechanism of slag beads were studied by combining the physical properties of BFS and the granulation effect. The results showed that the viscosity of BFS decreased with the increase of basicity; the bigger the basicity, the higher the bead formation rate, the smaller the particle size and the more regular the slag shape. The smaller the basicity, the greater the crystallization activation energy and the smaller the Avrami exponent, which indicated that the crystal was more difficult to nucleate and grow. The increase of the cooling rate could effectively inhibit crystal precipitation. Therefore, the high basicity and cooling rate could not only guarantee the high bead formation rate of BFS, but also ensure the high content amorphous phase of slag beads.

Experimental Study on Granulation of Blast Furnace Slag by Gas Quenching

Experimental Study on Granulation of Blast Furnace Slag by Gas Quenching