Heating Furnace Research Articles

A real-time temperature field prediction method for steel rolling heating furnaces based on graph neural networks

In the billet reheating process during steel rolling, the real-time and accurate prediction of the temperature field is a prerequisite for the dynamic regulation of the heating process, which is crucial for ensuring the quality of billet reheating and reducing the energy consumption of the reheating furnace. The most commonly used finite element thermal field simulation and analysis methods are unable to meet the demand for real-time prediction under dynamic working conditions. Furthermore, traditional machine learning methods struggle to handle irregular data that includes spatial location information, resulting in inaccurate temperature field predictions, which in turn affect the furnace control efficiency and the quality of the product. In light of these limitations, this study proposes a Graph Neural Network (GNN)-based temperature field prediction method for steel rolling reheating furnaces. This method considers the interactions between the nodes within the reheating furnace and constructs a temperature field topology graph to effectively capture these interactions, including heat conduction and convection. Additionally, in the feature fusion and state updating mechanism of the model, we introduce process parameters, such as the air-fuel ratio, as additional inputs to enhance the ability of the GNN to handle complex variables. This enables real-time accurate simulation of the internal temperature distribution of the reheating furnace. The experimental results demonstrate that the model prediction error is controlled within 2.9 % and the response time is maintained within 20 ms, thereby validating the reliability and efficacy of the method in practical applications.

Activation of NO with microwave irradiation for low temperature direct decomposition

Direct decomposition of nitric oxide (NO) on metal oxides under microwave (MW) irradiation was investigated and it was found that the most metal oxides show higher NO decomposition activity than that in the conventional electric furnace heating at low temperature. Among the examined oxides, it was found that TiO2, CeO2, ZrO2, and Y2O3 show about 95 % or higher NO conversion at 573 K, and both N2 and O2 are formed with almost equimolar amount. In particular, ZrO2 exhibited high and stable NO decomposition activity more than 25 h. In this study, the influence of coexisting gases on NO decomposition activity on ZrO2 under microwave heating was further investigated and the direct decomposition of NO can be proceeded even in the presence of 5 % O2, 5 % CO2, or humidified condition. Mechanism of high NO decomposition activity under MW irradiation was also studied and it was found that removal of oxygen from the catalyst was much increased under MW irradiation because of direct activation of oxygen and also direct activation of NO which is also suggested by pulse reaction.

Simulation methods for local microstructure evolution-cooling and time–temperature transformation behavior in heat treatment of tool steels

This paper presents the development of a simulative workflow capable of predicting microstructural evolution during heat treatment processes. It represents a meaningful advance in this field by extending existing simulation models previously published by the authors. In this previous work, the software solutions MatCalc®, MATLAB®, and Abaqus FEA® were coupled to calculate several local microstructural properties: the carbide content, the type, the distribution, and the chemical composition of the matrix. In addition, the model could determine the proportions of microstructural components such as martensite and retained austenite within the matrix. The hardening treatment was simplified by assuming a fast quenching, leading to complete martensitic phase transformation. However, this assumption may not be valid for larger components, leaving room for optimization. Therefore, the simulation model in this publication has been successfully extended to include local solution-state dependent time–temperature transformation behavior. In addition, an automated microstructure simulation of the entire component is now possible. As an application example, two tool geometries of different sizes were simulated with an identical furnace heat treatment. The same furnace temperature (T = 1050 °C) and the same holding time (t = 60 min) were simulated with a slow air cooling (Tair = 25 °C). The austenitizing temperature and holding time were chosen to dissolve a sufficient amount of carbides during austenitization, and the slow cooling rates were chosen to form diffusion controlled phases such as bainite or pearlite. To validate the simulation model, the simulated time–temperature sequences were reproduced experimentally in a quenching dilatometer. The resulting real microstructures were compared with the simulated ones.

TREATMENT OF COPPER FLUE DUST FROM FLASH FURNACE WASTE HEAT BOILER FOR IMPURITIES CONTROL

During the pyrometallurgical processing of copper sulphide raw materials, part of the charge leaves the furnace space together with the exhaust gases in the form of dust entrainment. Volatile components also pass into the dust-gas flow, due to which it is enriched with impurities, some of which are harmful to the technological process. The formed dust-gas flow passes through dust collection equipment, where the main part of it is captured. Most often, the captured dust is recirculated, which leads to a decrease in the productivity of the furnace unit and a gradual increase in the content of impurities in the condensed products of the smelting. To overcome these disadvantages, it is necessary to take part or all the recirculating dust out of the melting cycle and process it independently to extract the valuable metals and dispose of the harmful substances. In metallurgical practice, industrial application for the processing of recirculating dust entrainment has mainly been accomplished by hydrometallurgical methods based on treating the flue dust in aqueous solutions of acid or alkaline reagents. In the present research work, laboratory results on hydrometallurgical leaching of flue dust from a flash furnace waste heat boiler (FF-WHB) are presented. The effect of the main technological parameters affecting the degrees of recovery of the main metals in solution was studied. Based on the experimental results, the optimal conditionsfor hydrometallurgical treatment of the FF-WHB flue dust were determined. By treating the dust under optimal conditions, the main tasks of the research are achieved - removal of impurities harmful to the technological process and reduction of the amount of flue dust processed in the flash furnace.

Reproduction of decarburization caused by overheating in fire tube boiler material

One of the non-destructive testing methods for analysing fire tubes is the replica technique. This technique allows the investigation of microstructure, cracking, and high-temperature creep under operational circumstances without the cutting of the components. A cellulose-acetate foil was used to make a copy from the topography of the surface, which was suitable for microscopic analysis. In this paper, decarburization was generated in P355N fire tube material. The aim of the reproduction was to investigate the effect of overheating in boilers. The decarburization of the fire tube was made at different temperatures (300 – 900 °C) in an electric heating furnace. General deterioration and decarbonization began at 700 °C. A preliminary step of the decarburization was the transformation of the pearlite, which can be easily detected by scanning electron microscope. Grain growth could not be observed, and the particle size was unrelated to the thickness of the decarbonized layer.

Influence of heating elements layout on temperature uniformity in a large size heat treatment furnace

Computational Fluid Dynamics simulations were used to optimize heating elements placement on the walls of a large size electrical heat treatment furnace in order to reduce temperature gradients within the furnace and uneven temperatures on different faces of the blocks which could result in variabilities in final mechanical properties. Initial evaluations of different layouts highlighted the effectiveness of equipping two side walls. Subsequently, an optimal percentage of side wall coverage was identified through simulations and multi-objective evolutionary optimization. Genetic and pareto search algorithms yielded 10 % and 14.2 % as optimum values, respectively. Implementing an optimal coverage demonstrated significant reductions in surface temperature non-uniformity, surface-to-center temperature differential, and temperature differences between loaded blocks. These improvements suggest a potential for enhanced uniformity in mechanical properties across a batch of products. This approach presents a promising strategy for obtaining consistent and efficient heat treatment cycles in industrial heat treatment furnaces resulting in energy saving and improved product quality.

Preparation of bainite phase microstructure by laser-electromagnetic induction hybrid solid-state phase transformation

Increasing the proportion of bainite and martensite phases is one of the effective ways to enhance the toughness of medium-carbon low-alloy steel(42CrMo). In this paper, the surface heat treatment of 42CrMo steel is carried out by using a laser heat source to achieve complete austenitization, then with electromagnetic induction heating for several times to implement insulation, and eventually to promote bainite phase transformation. In conjunction with the temperature history curves, OM, SEM, and EBSD are used to characterize the bainite morphology and percentage of bainite via different parameters of the hybrid process. The results demonstrate that the hybrid process combined with twice electromagnetic induction heating can yield a considerable proportion of bainite phase in 42CrMo steel. The resulting duplex structure, consisting of bainite and a minor fraction of martensite, exhibits a significant increase (81.1%) in tensile strength, while maintaining similar impact toughness. The elongation after fracture only has a slight reduction of 5.5% compared to that of the substrate. This innovative process provides a practical alternative to traditional bainite isothermal treatment method which must perform in a heat treatment furnace. Therefore, it is presented as a promising solution for enhancing the mechanical properties of medium-carbon low-alloy high strength steels.

Unveiling Thermal and Athermal Effects in Strain Hardening Removal of A6061 Aluminum Alloy

AbstractThis study explored the application of a high-density pulsed electric current (HDPEC) to mitigate strain hardening in a cold-rolled A6061 aluminum alloy while examining the simultaneous application of HDPEC with furnace heating to reveal the contributions of thermal and athermal effects. The results showed that significant strain-hardening relief was achieved through the HDPEC treatment, particularly at 300 A/mm² for 260 ms, resulting in a 23% reduction in strength and an 86% increase in ductility. Microstructural analysis revealed a shift to fine and equiaxed grains with reduced dislocation density, which was primarily attributed to thermal effects. HDPEC annealing exhibits superior efficiency compared to the conventional annealing treatment, offering cost and time advantages. In addition, this study validated the synergistic impact of HDPEC and furnace heating, with furnace heating supplementing energy requirements, facilitating practical HDPEC implementation. These findings suggest that the HDPEC method and the combined method with conventional heating are promising alternatives for strain-hardening alleviation in A6061 aluminum alloy manufacturing, supporting the development of an eco-friendly and efficient process. Graphical Abstract

Mechanism of Working Fluid Circulation in the Multisource Organic Solid Waste Incinerator

Garbage incineration power generation is utilized to dispose of multi-source organic solid waste. This work constructed a mathematical model for a 750 t/d garbage incinerator to reveal the coupled response between the boiler and furnace sides. Field experiments validated the model, exploring various operating conditions including different loads, fuel blending ratios, primary air, and internal flue gas recirculation (IGR) air flow rates. Increasing the load by 9.1% raised furnace heat exchange by 4.0% but reduced economizer heat exchange by 19.0%. Introducing waste cloth strips and paper mill waste enhanced furnace water-cooled wall heat transfer but reduced economizer heat exchange. A 10.8% rise in primary air flow increased superheater heat exchange by 7.8%. Similarly, a 21.3% rise in IGR air flow increased economizer heat exchange by 9.0%. The temperature rise and enthalpy rise in the superheater were higher when the low calorific value of the fuel was higher. Increasing primary air velocity enhanced heat transfer, raising the outlet temperature of the medium-temperature superheater, necessitating an increase in secondary water spray to adjust the outlet temperature of the high-temperature superheater. This work provides guidance for the design and practical operation of multi-source solid waste incinerators.

Electrothermally-Driven Ultrafast Chemical Modulation of Multifunctional Nanocarbon Aerogels.

Ultrahigh-temperature Joule-heating of carbon nanostructures opens up unique opportunities for property enhancements and expanded applications. This study employs rapid electrical Joule-heating at ultrahigh temperatures (up to 3000K within 60s) to induce a transformation in nanocarbon aerogels, resulting in highly graphitic structures. These aerogels function as versatile platforms for synthesizing customizable metal oxide nanoparticles while significantly reducing carbon emissions compared to conventional furnace heating methods. The thermal conductivity of the aerogel, characterized by Umklapp scattering, can be precisely adjusted by tuning the heating temperature. Utilizing the aerogel's superhydrophobic properties enables its practical application in filtration systems for efficiently separating toxic halogenated solvents from water. The hierarchically porous aerogel, featuring a high surface area of 607m2g-1, ensures the uniform distribution and spacing of embedded metal oxide nanoparticles, offering considerable advantages for catalytic applications. These findings demonstrate exceptional catalytic performance in oxidative desulfurization, achieving a 98.9% conversion of dibenzothiophene in the model fuel. These results are corroborated by theoretical calculations, surpassing many high-performance catalysts. This work highlights the pragmatic and highly efficient use of nanocarbon structures in nanoparticle synthesis under ultrahigh temperatures, with short heating durations. Its broad implications extend to the fields of electrochemistry, energy storage, and high-temperature sensing.

Microstructure evolution in bituminous-coal pyrolysis under in situ and stress-free conditions: a comparative study

A self-made triaxial testing machine with thermal–hydraulic–mechanical–chemical (THMC) coupling and a tubular heating furnace, combined with in situ (IS) micro-computed-tomography technology was utilized in this study. The evolution of pore-fissure (PF) structure parameters (porosity, PF scale distribution, effective PF volume ratio, and permeability) of bituminous coal under stress-free (SF) and IS conditions with temperature was investigated, and then the mechanism of experimental results was analyzed. Results showed that (1) under SF conditions, at 300–550 °C, the coal samples after pyrolysis are dominated by elongated large fissures, with PF structure parameters positively correlating with temperature. After 400 °C, the number of PFs increases, with most PFs having equivalent diameter (R) ≤ 100 μm. (2) Under IS conditions, coal sample fissures are dominated by elongated large fissures at 300–350 °C and by holes at 350–600 °C. (3) Under IS conditions at 300–600 °C, the PF structure parameters of coal samples initially decrease with temperature and subsequently increase. The number of PFs fluctuates within a certain range, and the PF scale distribution dynamically shifts with temperature. (4) After 300 °C, the PF structure parameters of bituminous coal under SF and IS conditions show a bipolar distribution with temperature. Therefore, the weakening effect of stress on the PF structure of coal samples should not be overlooked during IS pyrolysis mining of coal bodies.

Improving the design of blast furnace blast regenerative devices by calculating coolant flows through the channels of the air heater nozzle

The air heaters used for heating blast furnace blast have recently undergone a number of design changes, which has affected their key thermal performance indicators. There are established temperatures at which settled operating conditions show sufficient technical and economic performance. Deviation from the conditions by increasing the temperature of the hot blast entails negative consequences of a different nature, which ultimately makes it unfeasible from an economic point of view. New design solutions for air heaters must be determined by maximum temperatures, which affects the service life of the equipment and system. Consequently, the development of the heat transfer surface of the nozzle plays an important role in solving the problem. Increasing the reliability of the apparatus and achieving high thermal performance indicators will result from improving the design of regenerative devices. By applying a mathematical model to the calculation of flows in a system of channels of an arbitrary given structure, calculations of coolant flows through the channels of a blast furnace heater nozzle were obtained. Modeling of flow non-uniformity at the inlet to the nozzle was carried out for different pressure fields at the inlet to the nozzle with horizontal channels. The results of the specified pressure fields at the entrance to the system and the results of calculating the mass flow rates of the coolant through vertical and horizontal channels are presented. It has been confirmed that the pattern of the pressure field at the inlet to the nozzle and the velocity field in the supply vertical channels are different due to the mutual influence of adjacent vertical channels because of their being connected into a single system by horizontal channels. Calculations have confirmed that horizontal channels do not actively participate in the heat exchange process. For better efficiency, it was proposed to make horizontal channels not along the entire height of the nozzle, but only in its upper and lower layers.

New MMO coatings for electro-refinery applications: Promoting the production of carboxylates

Within the new circular economy paradigm, this work evaluates the performance of tailored mixed metal oxides (MMO) anodes, based on ruthenium and antimony, for their application into an electrochemically-assisted organic refinery process. This process is designed to transform pollutants into value-added products with minimal mineralization. Oxidation of synthetic wastes consisting of phenol solutions was used to validate the electrochemical conversion of phenolic wastes into carboxylates, which are then considered as bricks to be used for electrosynthesis or to produce fuels. The MMO anodes were manufactured using two synthesis routes (Pechini method and ionic liquid method), each followed by one of three different heating treatments: furnace, microwave, and CO2 laser. The selection of the optimal electrode for the organic electrorefinery was based on a combination of physical and electrochemical properties, degradation performance of phenol to carboxylates, and long-term stability, looking for a truly sustainable solution. Results indicate that anodes synthesized by the ionic liquid (IL) method, regardless of the heating treatment, demonstrated superior performance, with larger active areas (with furnace 82 mC cm−2, microwave 97 mC cm−2, and laser 127 mC cm−2) and higher phenol degradation rates, resulting in a greater generation of carboxylates during electrolysis, yielding primarily oxalate and achieving up to 40% conversion with furnace heating. However, laser-treated anodes exhibited greater stability than furnace-made ones, attributed to the formation of an insulating TiO2 layer. Although the electrode with the longest service life did not show the best catalytic properties for minimizing mineralization, the observed variations in coatings with identical chemical compositions highlight the importance of this research. This study positions itself at the forefront of developing more efficient and sustainable electrochemical technologies for organic waste treatment.

Pyrolysis characteristics of different types of tobacco and its correlation with the released aroma components under heating condition

An in-depth insight into the pyrolysis characteristics of tobacco is of great significance for the utilization of tobacco wastes. The effects of glycerol addition on the pyrolysis characteristics and distribution of aroma components of four types of tobacco was investigated in this study by using thermogravimetry and self-built rapid heating furnace capture and GC-MS analysis. Further, correlation network analysis was used to study the correlation between pyrolysis characteristics and released aroma components. It was found that the thermal weight loss behavior of different samples exhibited both commonalities and differences, the thermal weight loss process could be divided into four stages. After the application of glycerol, the overall performance of all types of tobacco leaves at stage II showed that DTGmax2 and WL2 increased, and glycerol had a relatively obvious effect on the pyrolysis characteristic parameters of flue-cured tobacco. Pyrolysis kinetic analysis based on Coats-Redfern method showed that the activation energy and pre-exponential factor of tobacco samples were decreased after the addition of glycerol. Under the heating condition, the total amount of released aroma components from each type of tobacco followed the order of burley tobacco > flue-cured tobacco >oriental tobacco > yellow sun-cured tobacco. The release amount of heterocyclic and olefins compounds from burley tobacco were higher, while flue-cured tobacco released higher contents of esters, ketones and furans compounds. The addition of glycerol promoted the release of aroma components. In terms of correlation, Tmax2 was negatively correlated with esters, aldehydes, and furans compounds, and positively correlated with DTGmax3. Tmax3 was significantly correlated with a lot of indicators, positively with acids, aldehydes, and furans compounds, but negatively with olefins and heterocyclic compounds.

Efficient conversion of ethanol to acetaldehyde with induction heating at low temperature

The application of induction heating (IH) to provide heat for chemical reactions has received great attention due to its potential to electrify chemical reactions. Biomass-based production of acetaldehyde from ethanol has gained rising interest since it provides an alternative sustainable method instead of the fossil-fuel-based output using acetylene and formaldehyde in the presence of a catalyst. The dehydrogenation of ethanol can be catalyzed by supported copper catalysts. The reaction is typically carried out at high temperatures, around 250–300 °C, without oxygen. The resulting product mixture usually contains acetaldehyde, as well as other byproducts such as ethylene and hydrogen gas. The acetaldehyde can be separated from the other components using distillation or other separation techniques. In this work, we studied the catalyst activity with IH for the first time and achieved high ethanol conversion and acetaldehyde selectivity at a temperature of 30 ˚C lower than that with conventional furnace heating (CFH). A transport model was applied to design the catalyst bed configuration and improve the catalyst activity, stability, and energy efficiency by minimizing the temperature gradient. Our work suggests that the temperature distribution and the fast compensation of heat loss through IH are critical for the catalyst behavior. Both high production efficiency and energy efficiency can be achieved with IH, such that it can be an efficient and environment-friendly heating method for the chemical industry.

Optimization of Billet Cooling after Continuous Casting Using Genetic Programming—Industrial Study

ŠTORE STEEL Ltd. is one of the three steel plants in Slovenia. Continuous cast 180 mm × 180 mm billets can undergo cooling to room temperature using a turnover cooling bed. They can also be cooled down under hoods or heat treated to reduce residual stresses. Additional operations of heat treatment from 36 h up to 72 h and cooling of the billets for 24 h, with limited capacities (with only two heat treatment furnaces and only six hoods), drastically influence productivity. Accordingly, the casting must be carefully planned (i.e., the main thing is casting in sequences), while the internal quality of the billets (i.e., the occurrence of inner defects) may be compromised. Also, the stock of billets can increase dramatically. As a result, it was necessary to consider the abandoning of cooling under hoods and heat treatment of billets. Based on the collected scrap data after ultrasonic examination of rolled bars, linear regression and genetic programming were used for prediction of the occurrence of inner defects. Based on modeling results, cooling under hoods and heat treatment of billets were abandoned at the casting of several steel grades. Accordingly, the casting sequences increased, and the stock of billets decreased drastically while the internal quality of the rolled bars remained the same.

1.05 MW molten salt furnace experimental investigation of full-conditional thermal energy storage for the transfer and storage of waste heat from blast furnace gas

This paper proposes the use of heat storage devices and technologies to convert the unstable heat of gas generated by the iron and steel industry into stable heat, thus realizing the controllable and stable utilization of the gas waste heat. To this end, a 1.05 MW molten salt furnace energy storage experimental system was developed, utilizing a spiral coil type molten salt furnace to heat solar salt and achieve energy transfer and storage. The study comprehensively analyzes the preheating, heating, cooling, and special working conditions of the molten salt furnace. The experimental results demonstrate that the coils can be preheated within 150 min and heats the solar salt to over 570 °C at the rated load. However, the vertical and axial directions of the coil exhibit varying degrees of thermal stress under different operating conditions. In addition, the Reynolds number and Nusselt number of the heat transfer process were calculated and the convective heat transfer correlation equation was fitted using the similarity principle to find the heat transfer efficiency of the molten salt furnace of 77.12 %. These findings are expected to address the waste blast furnace gas issue and contribute to developing a sustainable energy system in the steel industry.

Study of the Effects on the Strengthening Mechanism and Wear Behavior of Wear-Resistant Steel of Temperature Controlling in Heat Treatment.

To improve the wear resistance of the materials used for blades in engineering machinery, this study focused on the microstructural characteristics, mechanical properties, and wear behavior of HB500 grade wear-resistant steel developed using an optimized heat treatment system. To improve the temperature uniformity of the heat treatment furnace, the method of cyclic heating was used to heat the components. Carefully designing the quenching equipment, such as using a cross-shaped press, was employed to enhance the quenching effect and reduce the deformation of the steel plates. The crystal orientation analysis revealed a uniform and fine-grained microstructure, primarily characterized by plate-type tempered martensite, which indicated a good hardenability. The microstructure observations showed that the width of martensite is approximately 200 nm, with a significant presence of dislocations and carbides. Tensile tests and multi-temperature gradient impact tests indicated superior mechanical properties compared to similar grade wear-resistant steels, including a Rockwell hardness of 53, tensile strength of 1610 MPa, yield strength of 1404 MPa, and total elongation around 12.7%. The results of friction and wear experiments indicate that the wear rate decreases as the load increases from 100 N to 300 N, demonstrating an excellent wear resistance under a large load. Observations of the worn surfaces indicated that the wear mainly involved adhesive wear, fatigue wear, and oxidative wear. The properties' improvements were attributed to microstructure refinement and precipitation strengthening. This study indicates that designing a heat treatment system to control temperature uniformity and stability is feasible.

Artificial neural network for predicting the performance of waste polypropylene plastic-derived carbon nanotubes

AbstractIn this study, an artificial neural network model using function fitting neural networks was developed to describe the yield and quality of multi-walled carbon nanotubes deposited over NiMo/CaTiO3 catalyst using waste polypropylene plastics as cheap hydrocarbon feedstock using a single-stage chemical vapour deposition technique. The experimental dataset was developed using a user-specific design with four numeric factors (input variable): synthesis temperature, furnace heating rate, residence time, and carrier gas (nitrogen) flow rate to control the performance (yield and quality) of produced carbon nanotubes. Levenberg–Marquardt algorithm was utilized in training, validating, and testing the experimental dataset. The predicted model gave a considerable correlation coefficient (R) value close to 1. The presented model would be of remarkable benefit to successfully describe and predict the performance of polypropylene-derived carbon nanotubes and show how the predictive variables could affect the response variables (quality and yield) of carbon nanotubes.

Effect of Heat Treatment on Mechanical Properties and Corrosion Response of HVOF Sprayed High Entropy Alloy Coatings

Surface and sub-surface related degradation of steels can be minimized using suitable surface coatings. High entropy alloys (HEA) are prominent and emerging materials among many coating materials. The current study investigates the effect of heat treatment of HEA coating on mechanical, metallurgical, and corrosion properties. The HEA coatings on SS304 steel were deposited using a High-Velocity Oxy-Fuel (HVOF) thermal spray process. The developed coatings were furnace heat treated at 700 °C, 900 °C, and 1100 °C, respectively, and their performance was benchmarked with the as-sprayed coatings. The metallurgical, mechanical, and microstructural analyses were performed using X-ray diffraction (XRD), Nanoindentation, Scratch test, and Field Emission Scanning Electron Microscope (FESEM) techniques. The corrosion response of the as sprayed and heat-treated coatings were recorded using a Potentiostat. The results indicated that as-sprayed coatings consisted of a single-phase BCC solid solution; however, the single-phase changed to a dual dual-phase system after heat treatment (BCC+FCC). The 900 °C heat-treated HEA coating exhibited superior mechanical and corrosion properties. But those characteristics started diminishing when the heat treatment temperature exceeded 900 °C. The introduction of the new FCC phase softened the coating, thereby leading to the evolution of microcracks in the coating. These micro-cracks acted as channels for electrolyte diffusion and further corroded the coatings. The current study surmised that HVOF-sprayed HEA coating should not be heat treated at above 900 °C.