Heat Treatment Cycles Research Articles

Effect of various surface heat treatment methods and its parametric variation on the hardness properties of different steels grades

In the current era of industry 4.0 automobile industry is playing a major role. The material used for making parts of automobile such as camshaft, screws, nuts, transmission shaft etc. is directly related to vehicle performance. So, it is necessary to choose particular material grades. In automobile industry EN1A, AISI 1018, AISI 1020, 20MnCr5B, SCr420H, S700MC, AISI A514, AISI 8620, SAE1141 commonly use and has many applications. This material grades are usually incorporated in the many automobiles’ application mention above. The aim of the present study is to improve the performance of existing material grades by various heat treatment cycle. In the present study, few materials grade are identified such as EN1A, 20MnCr5B, SCr420H, SAE1141, AISI 8620 and subsequent heat treatment such as carburizing, tempering, hardening and diffusion performed on it. Study performed by varying process parameter such as time in range from 0.5 h to 6 h and temperature ranging from 160 °C to 930 °C in inert atmosphere. Over-all in the post heat treatment on various grades, it has been found that hardness of the material grades improved in the outermost layer of the sample and same pertain to the microstructure.

Laser powder bed fusion of Alumina/Fe–Ni ceramic matrix particulate composites impregnated with a polymeric resin

Additive Manufacturing (AM) plays a key role in meeting the vital demands of Industry. The AM industry needs the range of applicable materials to be expanded by conducting research on novel ones. In the present investigation, alumina/Fe–Ni (steel) ceramic matrix particulate composite was fabricated employing laser powder bed fusion (LPBF) additive manufacturing (AM) technology. The quality of the printed samples was associated with the LPBF process parameters, which were optimized for this process. In general, the fabricated samples showed a microstructure of alumina matrix with uniform distribution of steel (Fe–Ni) particles. The as-printed samples exhibited pores. Thus, they were subjected to a sintering heat treatment cycle under an inert atmosphere. Although the sintering cycle considerably increased the average Vickers hardness, pores were not eliminated entirely. Therefore, polymer impregnation of the as-sintered samples was carried out to reduce porosities and microcracks. The mercury porosimeter showed that the porosity decreased sequentially after sintering and polymer impregnation. In addition, mechanical investigations revealed that the polymer impregnation improved the compressive strength of the sintered samples (from 56 to 120 MPa). Alumina-based materials find wide applications in various fields, including the manufacturing of electronic components, cutting tools, biomedical implants, and catalyst converters, owing to their low density, high hardness, wear and corrosion resistance, and biocompatibility. This study presents a viable approach for the fabrication of these materials, with developed samples exhibiting promising properties. The study emphasizes the potential of additive manufacturing as an approach for the fabrication of ceramic matrix composites reinforced with metallic particulates in future research.

Corrosion Protection and Heat Resistance of Paints for Outdoor Use.

Innovative heat- and corrosion-resistant coating approaches, applicable in indirect-food-contact outdoor environments, have been developed. Two systems, a direct-to-metal single-layer, polysiloxane-based, oven-dried system and a bilayer, zinc phosphate active pigment-containing, ambient-cured system were developed to overcome the shortcomings of the traditional bilayer, zinc-rich primer-based heat-resistant surface-protective solutions for outdoor cooking equipment, such as barbecue grills. This case study aims to optimize the application conditions, measure and evaluate the impact of surface preparation and compare thermo-resistant and anticorrosive properties of different coating systems focusing on eco-efficiency. The anticorrosion efficiency of the coatings was characterized using salt-spray chamber corrosion tests and electrochemical impedance spectroscopy. The thermo-resistant character of the coatings was tested by cyclic and constant heat treatment, after which the physical integrity of the coatings was evaluated by optical microscopy. In the overall performance of the coatings, the roughening of the steel substrate surface and the thickness of the coatings were also considered as influential parameters. The study revealed that the newly developed coatings have superior anticorrosion performance to the usually applied Zn-rich coating. The Single-layered Coating has excellent corrosion resistance under certain conditions and has the advantage of fast layer application. The Bilayered Coating showed excellent heat- and corrosion-resistance properties even on a surface without sand-blasting.

Convoluted filtering for process cycle modeling

AbstractPrinciples of materials science and engineering, physics, mathematics, and information science are used to extract knowledge and insights from the process‐structure–property‐performance relationships hidden in materials data. The process‐structure modeling can be accelerated without loss of interpretability, with artificial intelligence tools that mimic the salient features of the process and process‐structure relations. In this work, a novel convoluted model‐filtering technique was exploited to build and successfully train the Convoluted Filter (CoFi) artifacts for Fe‐based alloy heat treatment cycles. The artifacts were pre‐trained to filter out deep models that change the surrogate microstructure state after the heat treatment at ambient conditions. Direct representation of the thermal cycle features within knowledge Graph facilitated development of meaningful data models for microstructure evolution, which reduce overfitting to limited datasets.

Effect of Cyclic Heat Treatment on Microstructure Evolution of TA15 Titanium Alloy

Effect of Cyclic Heat Treatment on Microstructure Evolution of TA15 Titanium Alloy

Effect of cyclic heat treatment on abnormal grain growth in Fe-Mn-Al-based shape memory alloys with different Ni contents

Cyclic heat treatment that can continuously promote abnormal grain growth is widely used for the preparation of single‐crystal Fe‐Mn‐Al‐based shape memory alloys. However, it takes a long time to prepare large‐size Fe‐Mn‐Al‐based alloy single crystals via the reported cyclic heat treatments. Meanwhile, the long‐time cyclic heat treatment at high temperatures leads to the development of defects including oxidation and a decrease in Mn, which would deteriorate superelasticity in the Fe‐Mn‐Al‐based shape memory alloys. To shorten the fabrication time of single crystals, the effect of the cyclic heat treatment process on the abnormal grain growth in the Fe‐Mn‐Al‐based alloys with different Ni contents was systematically investigated. It is found that the abnormal grain growth of Fe‐Mn‐Al‐based alloys was not significantly affected by the Ni contents (within 2.1 at.%–6.2 at.%). In addition, the abnormal grain growth could be promoted by 1–2 °C min–1 cooling rate, high solution temperature, and multiple cycles, while it was insensitive to other processes including heating rate, dual‐phase time as well as long‐time solution treatment. These findings can guide optimizing the fabrication process of single crystals by cyclic heat treatment. Finally, the Fe41.9Mn37.8Al14.1Ni6.2 single crystal prepared by the optimized cyclic heat treatment showed a recoverable strain of about 4%.

Promoting the dissolution of delta ferrites by cyclic heat treatment in martensitic heat-resistant steel

Promoting the dissolution of delta ferrites by cyclic heat treatment in martensitic heat-resistant steel

Electron Beam Based Additive Manufacturing of Alloy 247 for Turbine Engine Application: From Research towards Industrialization

In this contribution it will be shown how the metal powder bed fusion technology electron beam melting (EBM) enables a successful crack- and defect-free processing of the non-weldable Ni-based superalloy Alloy 247. Besides a defect-free processing, EBM process capabilities offer unique opportunities to tailor the microstructure according to material requirements for high-temperature applications. It could be demonstrated that EBM material properties are comparable or even better than traditionally casted Alloy 247 material. Tailored polycrystalline and columnar microstructures were achieved by process parameter adoption for solidification control. The EBM as-built microstructure was characterized by conventional metallography techniques and the results were used to define an adopted HIP + heat-treatment cycle which was applied prior to mechanical testing. Thus, corresponding mechanical and microstructural properties in different conditions will be presented and discussed to show EBM material capabilities. As a result, directionally solidified (DS) EBM material can achieve similar creep performance as DS cast material, despite an observed fine-grained “micro-DS” structure in EBM.Graphical

Influence of Various Heat Treatment Cycles on the Phase Transformation and Microstructure Evolution of AISI 329 Super-Duplex Stainless Steel

The importance of duplex stainless steel in the global steel industries takes from its application because of its utilization in the environment, the paper industries, and pipelines and reactions champers found in the gas, oil, and chemicals industries. This research investigates the effect of various heat treatment cycles on the intermetallic compound precipitation and different constituents' evolution of the AISI 329 steel. Also, this investigation aims at exploring the relationship of the microstructure evolution at various heat treatment cycles and its effect on the tensile properties of selected steel. The phase transformation studies were conducted theoretically utilizing the JMatPro program and experimentally employing differential scanning calorimetry tests and dilatation; the obtained microstructure was inspected by exploiting a light metallographic microscope, a field-emission scanning electron microscope, and x-ray diffraction. The results illustrated that the microstructure includes ferrite, austenite phases, and dispersive particles. The dispersive particles are carbide particles and intermetallic compounds. Furthermore, the sigma phase settled at the boundaries of the ferrite grains. Intermetallic compounds were observed in both cast and heat-treated steel microstructures. Observed intermetallic compounds have no specific engineering geometry with various sizes, and the main alloying elements are Cr, Fe, and Mn. Special heat treatment, including solid solution and aging at high temperatures, leads to thinning of the sigma phase while diminishing the size of the intermetallic compound. Tensile properties were enhanced by controlling the volume fraction of different constituents that are adjusted by heat treatment. The fracture morphology is consistent with the microstructure and tensile properties of the investigated steel.

Experience of P93 manifold welding under fabrication conditions

ABSTRACT A test manifold of grade P93 is welded under shop fabrication conditions. Raw materials include pipe and forgings. Welding processes used are GTAW and SMAW. Weld joints involve heavy wall butt welds and branch joints. Welded joints are subjected to different heat treatment cycles to assess the effect on the materials’ properties. Welding experiences and mechanical test results in relation to PWHT and ageing are discussed. Tensile test results comply with the requirements. Achieving impact toughness requirements appears to be challenging, however improvements are expected through further optimisation of heat treatment and welding procedures.

Oxidation Behavior of NiCoCrAlY Coatings Deposited by Vacuum Plasma Spraying and High-Velocity Oxygen Fuel Processes

To reduce the formation of detrimental complex oxides, bond coatings in the thermal barrier coatings for gas turbines are typically fabricated using vacuum plasma spraying (VPS) or the high-velocity oxygen fuel (HVOF) process. Herein, VPS and HVOF processes were applied using NiCoCrAlY + HfSi-based powder to assess the oxidation behavior of the bond coatings for both coating processes. Each coated sample was subjected to 50 cyclic heat treatments at 950 °C for 23 h and cooling for 1 h at 20 °C with nitrogen gas, and the weight change during the heat treatment was measured to evaluate the oxidation behavior. After the oxidation test, the coating layer was analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The VPS coating exhibited faster weight gain than the HVOF coating because the alumina particles generated during the initial formation of the HVOF coating inhibited oxidation and diffusion. The VPS coating formed a dense and thick thermal growth oxide (TGO) layer until the middle of the oxidation test and remained stable until the end of the evaluation. However, the HVOF coating demonstrated rapid weight loss during the final 20 cycles. Alumina within the bond coat suppressed the diffusion of internal elements and prevented the Al from being supplied to the surface. The isolation of the Al accelerated the growth of spinel TGO due to the oxidation of Ni, Co, and Cr near the surface. The as-coated VPS coating showed higher hardness and lower interfacial bonding strength than the HVOF did. Diffusion induced by heat treatment after the furnace cyclic test (FCT) led to a similar internal hardness and bonding strengths in both coating layers. To improve the quality of the HVOF process, the densification of the coating layer, suppression of internal oxide formation, and formation of a dense and uniform alumina layer on the surface must be additionally implemented.

Rapid and reversible detection of trace amounts of H2S in air and packaged food using a biogenic bismuth oxide nanorod colorimetric sensor

A colorimetric reversible sensor has been developed for detection of trace amount of H2S gas in air and sealed meat packages. The active sensing area includes high surface area bismuth oxide (Bi2O3) nanorod prepared by green synthesis method. The as fabricated sensor demonstrates a rapid response in just 25 s for sensing 1 ppm H2S gas with distinct colour change in the active sensing area from white to brown. Sensing pellets were used to optimize the performance of the H2S sensor in terms of sensitivity and selectivity in air. Flexible nitrocellulose membrane filter papers coated with Bi2O3 were used to detect spoilage in packaged raw animal food products such as meat, poultry and fish. The sensor is reversible and can be recovered within a short cycle (3 min) of heat treatment at 300 °C. X-ray diffraction, Raman spectroscopy and band gap measurements confirmed partial conversion of Bi2O3 nanorods into Bi2S3 when exposed in the range of 1–100 ppm H2S gas.

Improvement of thermocyclic treatment technology to increase wear resistance of gears

The technology of thermocyclic treatment of fine‑module gears has been improved, which makes it possible to increase their wear resistance by 30–40 %. Gears were subjected to preliminary cyclic heating and subsequent impulse hardening. In all cases of hardening, a martensitic structure is formed, which provides high rigidity of the material. The sizes of martensitic plates depend on the heating temperature during quenching. During cyclic heat treatment up to a temperature of 450 °C, the sizes of austenite grains and martensite plates did not depend on temperature.

Reactive air aluminizing of a nickel-based superalloy (IN738LC): Coating formation mechanism

Reactive air aluminizing (RAA) based on a slurry route is a low-cost method with high efficiency to form aluminide coatings on surfaces where final coating microstructures are temperature and time-dependent. This study aims to incorporate the RAA method into standard heat-treatment cycles of IN738LC. Painted samples are solutionized, solutionized then aged, and only aged. Different samples are prepared at different stages of aluminide formation. FE-SEM surface morphology, BSE-SEM cross-sectional observations, surface XRD characterization, and comparing EDS elemental composition with Al-Ni-Cr phase diagrams are utilized to discuss the formation mechanism thoroughly. A classical high activity type of aluminide coatings with a triple-layered structure of β-NiAl and Cr-rich precipitates at the top coat, β-NiAl in the middle coat, and an IDZ is formed by the RAA method. A three-stage formation mechanism, including the reactive stage (interaction between molten Al and solid substrate), Al-inward diffusion at low and Ni-outward, and Al-inward diffusions at high temperatures, is proposed in detail. After heat-treatment cycles, a ~3 μm aluminum oxide protective scale is detected on the sample surfaces. γ-Al2O3 and α-Al2O3 are formed during only aging at 845 °C and solutionizing at 1120 °C on sample surfaces, respectively.

Modeling and simulation through multi-criteria approach for customized conveyor-type industrial oven handling wide variety of metal structures

Modern ovens are utilized from large span of time for completing different heat treatment cycles like baking, curing, annealing, aging, drying, and so on. There are numerous sorts of industrial ovens namely batch, relieving, drying, baking, reflow, clean room, conveyor types, and so on. Conveyor oven helps to perform the heat treatment cycle in an uninterrupted flow, including the heating of the objects followed by the cooling down of the same object. A multipurpose conveyor-type industrial oven is designed using analytical approach for heat treatment process on various objects. This article presents the modeling and CFD analysis of conveyor-type continuous ovens. Simulation of the entire model of conveyor-type industrial oven is carried out in Solidworks Flow package. Since the boundary conditions of an actual industrial oven is open at both entry and exit points, same condition is maintained in the CFD analysis. With the help of the simulation model, researchers can study and observe the temperature distribution throughout the oven.

Effect of forging sequence and heat treatment on microstructure of high-duty power-plant shaft made of Cr-Mo ultra-high strength steel

The paper presents results of modeling and testing of a heavy weight part made of Cr-Mo, which was V-modified ultra-high strength steel grade AISI 4140, processed through a novel open-die forging schedule and two alternative routes of two-stage heat treatment cycles designed to meet requirements of high-duty components for energy sector. Taking advantage of unconventional forging conditions based on assumption of large feed and reduction ratios and the modification of chemical composition better control of austenite grain was achieved to minimize abnormal grain growth and/or strain uniformity problems. With aid of Finite Element Modeling of multi-stage sequence of upsetting and cogging strain distribution was optimized so as to minimize strain fluctuations on the length to range 2.2?2.7,and correlated with microstructure produced at every major stage on the large cross-sections of the shaft. Designed with aid of finite element method processing cycles was verified in full-scale physical modeling with use of 16 ton forging ingot, including two alternative quenching strategies: oil vs. water spray and air. Examination of material in as-forged, normalized and heat-treated condition was carried out to observe response of hot-worked material and the effect of cooling conditions on microstructure during final heat treatment. As observed, employing large feed ratios on cogging and varied cooling allowed suppress detrimental effect of inevitable abnormal grain growth which resulted in 1-2 ASTM grain in as-forged conditions to reach 6 ASTM in normalized and 8/9 ASTM after quenching in oil and water spray, respectively, which allows producing after tempering, correspondingly, 44?48 and 85?122 J/cm2 V-notch impact strength in the critical area of the forged shaft.

Структура сплавов для постоянных магнитов типа (Sm,Zr)(Co,Cu,Fe)z и механизм формирования высококоэрцитивного состояния

Owing to the high temperature stability of hysteretic characteristics and corrosion resistance under external actions, (Sm,Zr)(Co,Cu,Fe)z-based magnets are widely used in devices operating at high temperatures, most critical constructions of aerospace engineering and defense technology, and in traction electric motors for transport engineering. A number of modern research methods are used to study in detail the structure and phase composition of the (Sm,Zr)(Co,Cu,Fe)z alloys with z = 5.5 – 7.0 in as-cast state and after heat treatment, which includes the solid solution treatment at 1150 – 1180 °С for 5 h, subsequent water quenching, isothermal aging at 800 °С for 20 h, and cooling (stepped aging) from 800 to 400 °С at an average cooling rate of 100 °С/h. The results obtained allowed us to suggest the schematic diagram of grain-boundary constituent transformation at different stages of heat treatment of (Sm,Zr)(Co,Cu,Fe)z permanent magnets prepared by powder metallurgy. The formation mechanism of high-coercivity state of (Sm,Zr)(Co,Cu,Fe)z permanent magnets in the course of complete heat treatment cycle is given as the sequence of phase transformations accompanied by redistribution of a number of alloy components.

Effect of heat treatment on the precipitation of Mg17Al12 in Mg-7Al alloy

Mg–7Al alloy is synthesized using a protective atmosphere electrical resistance furnace in which both the melting and casting compartments have provision for operation under a protective atmosphere. The maximum solid solubility of Al in Mg is around 12 wt% at 437 °C and is decreased to 0.1 wt% at room temperature as dictated by the phase diagram. Microstructural observation of the cast structure confirmed that most of the aluminium present in the alloy forms a eutectic β phase segregated around the grain boundaries of α-magnesium and hampered the mechanical properties significantly. To understand the precipitation behaviour, the Mg alloy is heat treated employing three sets of heat treatment cycles. The cast Mg alloy is solutionized at 420 °C for 24 hrs and then quenched in ice water at 7 °C to achieve a supersaturated solid solution (SSSS). The quenched samples are aged at 350 °C, 227 °C, and 150 °C for 8, 10, and 12 hrs respectively. The microstructure confirms that the alloy aged at 350 °C, forms continuous precipitation of β-phase whereas the alloy aged at low temperature i.e., at 150 °C forms discontinuous precipitation, while the sample aged at intermediate temperature i.e., 227 °C both the continuous and discontinuous precipitation are observed. Vickers hardness values of the solutionized sample are 48 ± 3 HV and aged at 350 °C, it is 55 ± 5 HV. At low-temperature ageing i.e., at 150 °C the hardness value is decreased to 44 ± 5 HV, whereas ageing at 227 °C, the hardness value is found 53 ± 5 HV.

Enhanced strength-plasticity matching of lamellar 1 GPa-grade dual-phase steels via cyclic intercritical quenching

In this work, an innovative cyclic intercritical quenching process has been proposed for achieving excellent mechanical properties in terms of strength and plasticity, which results in a lamellar martensitic-ferritic dual-phase steel. The microstructural evolution under cyclic heat treatment was thoroughly investigated, and the mechanism that enables the lamellar structure to enhance its strength-plasticity matching was also explored. The experimental results revealed that the incomplete austenitization process inhibits the coarsening of the reversed austenite, and the cyclic intercritical quenching procedure finer and more evenly distributes the reversed austenite. The single intercritical quenching (C1) generated mostly massive martensite with traces of ferrite, whereas three-cyclic intercritical quenching (C3) yielded a fine and uniformly distributed lamellar structure. A comparison in terms of the mechanical properties between C3 and C1 steels indicates that uniform elongation, total elongation, and the product of strength and uniform elongation of the C3 steel increased by 85.4%, 47.3%, and 65.0%, respectively, while ultimate tensile strength was dropped by only 11.0%. In addition, the yield ratio of C3 steel is just 0.48. The slight decrease in strength is due to the fine lamellar microstructure. The high plasticity is attributed to the good deformation compatibility between lamellar ferrite and lamellar martensite with excellent plastic deformability. Therefore, cyclic mechanical heat treatment is very promising for the production of low-cost dual-phase steels.

Effects of cyclic heat-treatment in air on optical performances of AlCrSiO-based solar selective absorber

Higher working temperatures could help to improve the solar-electricity efficiency of concentrating solar power plant. However, the high temperature also induces structure variations and optical degradation of solar absorbers, and how the structure evolutions affect the optical performances remains largely unclear. To address the problems, we conducted cyclic heat-treatment on the AlCrSiO-based solar selective absorbers at a temperature of 650 °C. Then the microstructures and optical properties of the absorbers before and after annealing were systematically investigated. Finite-Difference Time-Domain simulations were used to establish the relationships between the microstructures and optical properties. The results showed that the absorber can maintain its multilayered structure after cyclic heat-treatment at 650 °C in air with a solar selectivity of 0.928/0.171. Oxidation of micro-droplets on surface can enhance solar absorption in the UV–Vis region due to the reduction of backscattering. The weak oxidation of the absorbing layers would lead to the enhancement of interference effects in the whole solar spectrum. The combination of the above effects can actually enhance the solar absorptance. The diffusion of carbon from the substrate into the infrared reflective Cr layer would slightly improve the thermal emittance. These results suggested the AlCrSiO-based solar selective absorber can be a possible candidate for applications in the next-generation concentrating solar power plant system.