Preheat Temperature Research Articles

Use of hydroxyapatite powder derived from green mussel shell wastes for coating on AISI 316L

This study aimed to determine the effect of preheating AISI 316L metal substrate on the adhesion strength of the hydroxyapatite (HA) layer derived from green mussel shell waste deposit by the flame spray method. The deposition experiment was carried out in a spray gun with a distance of 10 mm with preheat of 200°C, 400°C, and 600°C. A sample without preheating was also a comparison. An optical microscope was for assessing the thickness and uniformity of the HA surface layer. The adhesion strength of the coatings followed the ASTM D4541 Standard. As a result, the adhesion strength of the HA coating increases with increasing preheat temperature. However, using Image-J software, at an initial heating temperature of 600 °C, the adhesion strength of the coating changed from adhesion- to adhesion-cohesive strength, leading to an increase in coating strength noted. The result can add knowledge to understanding the flame spray method for the HA-coated from green mussel shell waste on AISI 316L. The results obtained can increase knowledge to understand the method of flame spraying on HA-coated green mussel shell waste on AISI 316L. Preheat temperature, spray gun shooting distance, HA powder release, oxygen gas pressure, and LPG gas pressure can be used as references.

Repairing High γ’ Hot Section Gas Turbine Components Using Advanced Manufacturing

This article describes the ability to use laser-blown powder deposition to repair high γ’ IN-100 superalloy gas turbine components. The influence of various process conditions on the ability to make crack-free IN-100 deposits over surrogate high γʹ alloys was investigated to identify cracking mechanisms in the deposit and heat-affected zones (HAZs). The various crack formation mechanisms, such as solidification cracking and liquation cracking, were evaluated using multiscale characterization and numerical simulation. The cracking in the deposit region was predominantly solidification cracking, while those observed in the HAZ were liquation cracking. The results showed that controlling thermally induced residual stresses is the key to eliminating cracking, and the optimum preheat temperature was determined. The results were then contrasted with those in published literature and an approach to effectively repair hot section parts was presented.

Effect of Preheat Temperature Variation with Cooling Media on Mechanical Properties in Welding SS400 Steel

Effect of Preheat Temperature Variation with Cooling Media on Mechanical Properties in Welding SS400 Steel

Experimental study on the flexible peak shaving with pulverized coal self-preheating technology under load variability

The integration of renewable energy sources into power grids has led to power fluctuations, necessitating coal-fired power units to provide flexible peak shaving. The pulverized coal self-preheating technology can potentially provide broad-load regulation and rapidly respond to load changes. In this study, the impact of the self-preheating technology on fuel preheating modification, combustion characteristics, and NOx emissions are investigated. Load-stabilization bases are proposed based on preheating temperature, preheated coal gas composition, combustion temperature, and flue gas emissions. Load change rates are calculated using these bases to character the load response. The results demonstrate that the preheated fuel has similar properties as the highly reactive gaseous fuel and exhibits excellent ignition and combustion performances at 25 % load. Preheating treatment improves combustion efficiency, and burnout ratio and reduces NOx emissions. The NOx concentration approaches the ultra-low emission standard at 50 % load. Four load-stabilization bases, covering the preheating and combustion sides, comprehensively characterize the load response performance. The rates based on preheating indicators and combustion indicators maximize to 3.30 %/minute and 2.71 %/minute, respectively. The load change rate in the ramp-up phase is higher than that in the ramp-down phase, which is related to the effective internal heat storage carrier and external thermal insulation conditions. The driving force formed by high load step ranges and the deviation from the full load capacity are conducive to increasing the load change rates.

High Energy Density Welding of IN792 Ds Superalloy

Ni base superalloys are commonly employed in the industrial fields of aerospace, automotive and energy production due to their excellent mechanical properties and corrosion resistance at high temperature. Superficial defects and cracks may occur during both manufacturing process of components and their service life. High energy density welding techniques, electron beam (EBW) and laser beam (LBW) welding, can be used to create efficient repairs. Joints, obtained by EBW and LBW of IN792 directionally solidified (DS) superalloy, have been investigated to determine the presence of defects, and evaluate the mechanical properties related to specific microstructural features. The results showed that a pre-heating temperature (PHT) higher than 200 °C is always necessary to prevent the formation of hot cracks in the molten zone (MZ) and heat affected zone (HAZ). The process parameters have been optimized to get a good quality of the seams (lack of macro-defects, a good penetration depth and width). Some preliminary test of post-welding heat treatments (PWHTs) have been investigated to homogenize as far as possible the microstructure and the mechanical properties across the seams. The results obtained by the two techniques, EBW and LBW, have been compared and discussed.

Microstructures and properties of polymer-derived hexagonal boron nitride fibers with initial gradient oxygen contents

Oxygen plays a crucial role in the synthesis of boron nitride (BN) and the preparation of BN ceramics. The effects of oxygen content on the microstructure and properties of BN fibers treated at 1600 °C have not been studied yet. In this work, polymer-derived BN fibers are cured at 300 °C under oxygen and pyrolyzed at 600 °C, 700 °C and 800 °C under ammonia as the pre-heated BN fibers. Then, these pre-heated BN fibers are treated at 1600 °C under nitrogen as the final BN fibers. The compositions and microstructures of the pre-heated and final BN fibers are investigated. As the pre-heated temperature increases, the oxygen contents of the pre-heated BN fibers decrease to 24 wt%, 17 wt% and 5 wt%, respectively. The structures of the pre-heated BN fibers transform from amorphous BN to turbostratic BN. The oxygen in the pre-heated BN fiber volatilizes as boron oxide during treatment at 1600 °C, promoting the formation and growth of h-BN in the final BN fiber, with the maximum grain size reaching 74 × 20 nm (La × Lc). As the grain size of the final BN fiber increases, the Young's modulus, density and oxidation resistance level of the BN fiber improve, and the dielectric properties decrease. The final BN fiber that underwent pre-heating at 700 °C has the best comprehensive properties, with a tensile strength of 1.11 GPa and a Young's modulus of 265 GPa. This study researches the relationship between composition, structure and performance, and provides a scientific basis for the preparation process of BN fibers.

Laser-Powder Bed Fusion Additive Manufacturing of NiCrBSi Self-Fluxing Nickel Alloy, Material Health - Process Relationship

Laser Powder Bed Fusion (L-PBF) might be a promising solution for producing complex wear-resistant parts from NiCrBSi self-fluxing nickel alloys. This study investigates a large set of parameters with a baseplate heated up to 500 °C. Furthermore, laser remelting is also explored to further increase surface density and reduce cracking. Material health is deeply investigated by image analysis to quantify different defects (lack of fusion, porosity and cracks). Spatters likely induce lacks of fusion, while the low toughness and high hardness values cause cracks. The lack of fusion surface fraction and crack length decrease with the preheating temperature while the crack width increases. A surface density of 99 % is obtained with careful process optimisation leading to a laser power of 100 W, a laser speed of 750 mm.s-1 and a preheating temperature of 500 °C.

Cracking mechanisms and effect of extensive preheating in CM247LC and IN713LC Ni-base superalloy processed by Laser Powder Bed Fusion

Laser powder bed fusion processing of non-weldable γ’-strengthened Ni-based superalloys is challenging due to various cracking mechanisms that occur during the solidification and cooling stages of the materials. The current study offers an insight into the failure mechanisms of the CM247LC and IN713LC alloys, identifying the pre-heating temperatures which can mitigate cracking phenomena during processing. The adopted methodology involved the alloy processing by a standard Laser powder bed fusion system followed by microstructural characterization. It was confirmed that the development of cracks with a length in the range of 100–500 µm became evident in both alloys. High-temperature preheating strategies were then investigated using a simplified approach based on single laser track remelting. At pre-heating levels up to about 900 °C, corresponding to measured cooling rates of the order of 104 °C/s, hot cracks were still observed in the alloys due to γ’ precipitation and segregation of carbide former elements at the cell boundaries according to both microstructure observations and thermodynamic predictions. Preheating conditions at higher temperatures targeting levels above the γ’-solvus temperature, exceeding 1200 °C could promote slower cooling rates, leading to full suppression of cracks in the investigated γ’-strengthened alloys.

Towards Industry 4.0 and Sustainable Manufacturing Applying Environmentally Friendly Machining of a Precipitation Hardened Stainless Steel Using Hot Turning Process

This study aims to address the aforementioned challenges, solutions and implementation perspectives with regard to sustainable manufacturing. In this research, the conventional and hot turning of AISI630 hardened stainless steel have been investigated using PVD-(Ti,Al)N/(Al,Cr)2O3 coated carbide cutting tools at various feed rates and cutting speeds. The high hardness of AISI630, along with the low thermal conductivity, has made it one of the most difficult-to-cut materials, and consequently, its machining is associated with high tool wear and poor workpiece surface quality. AISI630 stainless steel is used in the manufacture of pressure vessels and components exposed to high-stress and corrosive environments in the oil and gas industries. In the present research work, tool flank wear and crater wear mechanisms have been studied in different cutting conditions as well as different preheating temperatures using SEM microscopy. Experimental results showed that hot turning operation at temperatures up to 300 °C reduces flank wear by 33% and improves machined surface roughness by 23%. In addition, FEM simulation has been developed to predict tool tip temperature and cutting forces during turning processes. Experimental and FEM analysis shows that cutting force reduction at a preheating temperature of 300 °C is one of the reasons that reduces tool wear compared to conventional turning. Moreover, it has been shown that by increasing preheating temperature in hot turning, the hardness of the carbides in the workpiece decreases more than the hardness of the tool substrate and reduces coating materials, consequently reducing cutting tool abrasion wear phenomenon.

Energy efficiency analysis and optimization of a pressurized oxy-fuel circulating fluidized bed combustion system

The commercial application of oxy-fuel combustion technology is limited by energy deduction which is caused by addition of air separation unit (ASU) and carbon dioxide compression and purification unit (CPU). Pressurized circulating fluidized bed (CFB) oxy-fuel combustion technology is one option to improve the net electric generation efficiency. In this research, a series of simulations and optimizations were carried out to analyze the energy efficiency of a pressurized oxy-fuel combustion system. The boiler structure and heat exchange surface arrangement under different pressure were calculated. The cross-sectional area of the furnace and tail flue were both reduced up to 10 % of the original size and the floor space of the boiler was considered to be the lowest at 1.1 MPa. The energy efficiency and exergy analysis were used to explore the influence of pressure on the net efficiency and the optimization potential of system. The net electric generation efficiency reached a maximum value of 24.16 % at 1.1 MPa, which is 5.4 % higher than that at atmospheric pressure. Finally, four parameters, i.e. preheat temperature, oxygen concentration, ASU outlet oxygen purity and CPU compressor outlet pressure, were optimized to improve the system net efficiency to 26.67 %, 29.04 %, 25.87 % and 24.36 %, respectively.

Rancang Bangun Mesin Sangrai Sampel Biji Kopi Elektrik Kapasitas 250 Gram

Coffee is one of the beverages with a distinct flavor profile. Coffee production continues to grow in response to community demands. A wide variety of coffee flavors have been developed, necessitating an effective coffee processing method, such as roasting. While many coffee production processes employ roasting machines with high capacities, smaller industries may incur losses when using such machines due to their production needs, which involve creating new coffee flavor samples. To address these challenges, a solution is proposed: the creation of a drum-based coffee bean sample roasting machine that utilizes the convection method. The machine manufacturing process involves calculating the drum capacity, heater specifications, motor rotation, and air flow. A 2000 Watt heater is chosen, accompanied by a maximum drum capacity of 250 grams. The driving motor is a 12 V DC motor. The combined power of the motor components totals 1520 Watts, and the overall heating capacity can achieve temperatures of up to 300ºC. Performance testing of the roasting machine is conducted under conditions where all components are functioning correctly. The final roasting results exhibit even distribution, with a preheating temperature range of 190-200ºC for approximately 15 minutes roasting time.

Influence of the Gas Preheating Temperature on the Microstructure and Electrical Resistivity of Copper Thin Films Prepared via Vacuum Cold Spraying

Vacuum cold spraying (VCS) has emerged as an environmentally sustainable method for fabricating ceramic and metal films. A high particle impact velocity is a critical factor in the deposition of metal particles during the VCS process, which can be significantly enhanced through gas preheating. This study employs Computational Fluid Dynamics (CFD) simulations to investigate the substantial impact of gas preheating temperature on particle impact velocity and temperature. Elevating the gas temperature leads to higher particle impact velocity, resulting in severe deformation and the formation of dense copper films. The experimental results indicate improvements in both film compactness and electrical properties with gas preheating. Remarkably, the electrical resistivity of the copper film deposited at a gas preheating temperature of 350 °C was measured at 4.4 × 10−8 Ω·m. This study also examines the evolution of cone-shaped pits on the surface of copper films prepared on rough substrates. VCS demonstrates a self-adaptive repair mechanism when depositing metal films onto rough ceramic substrates, making it a promising method for ceramic surface metallization.

Study on the Effect of Preheating Temperatures on Melt Pool Stability in Inconel 718 Components Processed by Laser Powder Bed Fusion

Laser Powder Bed Fusion (L-PBF) is one of the most widespread, versatile, and promising metal Additive Manufacturing (AM) techniques. L-PBF allows for the manufacturing of geometrically complex parts with good surface characteristics. In this process, in order to minimize the heat loss in the first layers of printing, the building platform is preheated to a temperature ranging between 80 and 250 °C. This aspect turns out to be very critical, and further investigation is needed for situations where the part to be printed is only a few layers high, as is the case in sensor printing. This work aims to investigate the melt pool stability under a variation in the preheating temperatures. We investigate the distance from the building platform, considering the number of layers printed. This is where the melt pool reaches its stability in terms of depth and width. This aspect turns out to be of remarkable importance for ensuring the structural integrity of parts with a few layers of height that are processed through L-PBF, such as sensors, which are proliferating in different industries. Thus, two case studies were carried out on IN718 superalloys at 40 and 60 microns of layer thickness and a preheating temperature of 170 °C on the machine. The results obtained show that after 1.2 mm of distance from the building platform, the melt pool reached its stability in terms of width and depth dimensions and consequently for the melting regime.

Novel blue diode laser cladding for high-performance nickel-based coatings on copper substrates

The high reflectivity and excellent thermal conductivity exhibited by copper substrates pose considerable challenges for conventional laser cladding techniques aiming to achieve high-performance coatings on their surfaces. In this study, a novel blue diode laser cladding approach was proposed to prepare nickel-based coatings on copper substrates. Under the conditions of a preheating temperature of 200 °C and laser power of 1500 W, a Ni60A coating was successfully fabricated on the surface of pure copper, with metallurgical bonding achieved and no crack defects observed. The average microhardness of the coating ranges from 468 HV0.1 to 775 HV0.1, which is approximately 8.8–14.6 times greater than that of the copper substrate. Furthermore, the wear resistance of the coating is approximately 3.6–4.7 times higher than that of copper at 25 °C, and approximately 3.8–5.4 times higher at 300 °C. The performance of the coating exhibit gradient variations in the cladding direction. Consequently, the challenges posed by the high laser reflectivity and the need for a high preheating temperature of copper substrate have been effectively overcome through the utilization of a blue laser cladding, facilitating the industrial-scale preparation of large-area coatings on copper components.

Spray Flame Characterization of a Dual Injector for Compact Combustion Systems

ABSTRACT The scalability of liquid fuel operated jet stabilized combustion system toward scales and mixing timescales relevant for corresponding micro gas turbine systems is impeded by the lack of suitable injection concepts. The high momentum of the combustion air jet can deteriorate the spray quality of conventional injection systems. In combustors with reduced mixing timescales (e.g. MGT and compact aero-engines) this results in elevated emissions and a prompt primary atomization is essential. For this purpose, a canonical confined jet spray burner is developed and equipped with a novel in-house dual-pressure swirl/airblast injection concept. An extensive parameter variation on the jet bulk velocity (80 , equivalence ratio (0.6 , combustion air preheat temperature (500 (K) 800) and premixing length (0.0 (mm) ≤ 48) is conducted to delineate the operational range. The spray process originating a partially premixed and a direct injection case is characterized by means of phase Doppler interferometry and shadowgraphy. The combustion process is described via OH*-chemiluminescence, flame photographs and exhaust gas measurements. The results show that the developed injection system yields Sauter mean diameters predominantly below 25 μm over the entire parameter range due to robust and prompt primary atomization. Moreover, the primary atomization process of the dual injector is sufficient under all conditions to confine secondary atomization close-to the combustor nozzle exit. The flame stabilization and reaction progress are more sensitive to the air preheat temperature than the bulk jet velocity variation as the mixture homogenization is limited by the vaporization process. Moreover, with decreasing reactivity (i.e. equivalence ratio and preheat temperature) the flame stabilization is increasingly dominated by the recirculated hot exhaust gas, indicating a transition from conventional turbulent flame propagation to auto-ignition influenced reaction progress. The resulting NOx and CO emissions approximate the values measured previously in related methane powered combustion systems. Consequently, the developed injection system is promising to expand the flexibility of compact gas turbines to liquid fuels while maintaining low emissions.

SELECTION OF TECHNOLOGICAL PARAMETERS OF MODES FOR MANUAL ARC WELDING OF SHUT-OFF VALVES MADE OF STEEL ALLOYED WITH 3–4 % NICKEL

Body of ball valves can be manufactured from A350-LF3 steel according to the US standard ASTM A350, alloyed with nickel up to 4 %. This steel has a tendency to harden in the heat affected zone during welding. The results of computer simulation showed that cooling rates during shielded metal arc welding exceed the recommended range. This can lead to the formation of hardening structures, the development of cold cracks and a decrease in the performance properties of welded joints of ball valves made of A350-LF3 steel.
 To prevent the formation of cold cracks, the preheating and concurrent heating temperatures were calculated. According to the results of computer simulation, it was found that pre-heating and concurrent heating provide the cooling rate of heat affected zone in the recommended range.
 The technology has been developed for welding ball valves made of A350-LF3 steel with mounting nozzles. This technology prevents the formation of cold cracks and provides a high level of strength and toughness of welded joints. The high level of mechanical properties of welded joints is confirmed by results of mechanical tests and metallographic studies.

Synthesis of Submicron-Sized Spherical Silica-Coated Iron Nickel Particles with Adjustable Shell Thickness via Swirler Connector-Assisted Spray Pyrolysis.

Silica-coated iron nickel (FeNi@SiO2) particles have attracted significant attention because of their potential applications in electronic devices. In this work, submicron-sized spherical FeNi@SiO2 particles with precisely controllable shell thickness were successfully synthesized for the first time using a swirler connector-assisted spray pyrolysis system, comprising a preheater, specific connector, and main heater. The results indicated that the thickness of the SiO2 shell can be tuned from 3 to 23 nm by adjusting the parameter conditions (i.e., preheater temperature, SiO2 supplied amount). Furthermore, our fabrication method consistently yielded a high coating ratio of more than 94%, indicating an excellent quality of the synthesized particles. Especially, to gain an in-depth understanding of the particle formation process of the FeNi@SiO2 particles, a plausible mechanism was also investigated. These findings highlight the importance of controlling the preheater and SiO2 supplied amount to obtain FeNi@SiO2 particles with desirable morphology and high coating quality.

Mechanics, damage and energy degradation of rock-concrete interfaces exposed to high temperature during cyclic shear

Shear properties of the rock-concrete interface are critical to the stability of deep underground engineering projects, particularly in high-temperature environments caused by geothermal activity, fire or nuclear waste radiation. A series of cyclic shear tests were performed on the pre-heated sandstone-concrete interface under both CNL and CNS conditions. The study carefully examined the degradation characteristics of shear mechanics, as well as the evolution of interfacial damage and energy, during cyclic shear of rock-concrete interface. The experimental results show that the pre-heating temperature and the number of shear cycles have considerable effects on the adhesion, shear strength, normal deformation, shear stiffness and friction coefficient of the sandstone-concrete interface, especially under CNS conditions. Furthermore, the nonlinear evolution of interfacial damage and energy release during cyclic shear is highly dependent on the pre-heating temperature. These test results provide valuable insights for revealing the mechanical degradation and evaluating the shear performance of rock-concrete interfaces in deep underground engineering projects subjected to high-temperature environments.

Tensile Strength Enhancement Via Heat Treatment In Directly Recycled Aluminium Alloy (AA6065)

Products made through solid-state recycling of aluminum chips in a hot extrusion process were regulated by temperature-related factors by utilizing a preheating temperature of 350 °C, 400 °C, and 450 °C for one hour, two hours, and three hours of preheating time, respectively. Design of Experiments (DOE) was used, and the findings showed that the preheating temperature is more significant to manage than the preheating duration, and that increasing the temperature led to a high tensile strength. This conclusion was reached as a result of the experiments. The profile that was extruded for three hours at 550 degrees Celsius had reached the ideal condition for achieving the highest possible tensile strength. The heat treatment was carried out with the solution temperature set at 450 degrees Celsius for two hours, and the ageing procedure was carried out at 195 degrees Celsius for three hours. The extruded specimen underwent heat treatment, which resulted in a considerable increase in its tensile strength.

High Yield Synthesis of Green Pyrolytic Oil via Thermal Cracking of Ricinoleic Acid Methyl Ester

AbstractCastor oil has the potential to be a renewable resource for the synthesis of high‐value‐added chemicals. This work focuses on the thermal cracking of ricinoleic acid methyl esters (RAME), the major component of castor oil in a micro fixed bed reactor that was used to produce methyl undecenoate (MU) and heptaldehyde (HEP). MU and HEP have wide applications in polymers, cosmetics, and drug industries. The effect of flow rate, sweeping gas flow rate, preheating and reaction temperatures were examined briefly. Thermal cracking of RAME at a preheating temperature of 350 °C and reaction temperatures of 550 °C, produced high yields of MU and HEP at 46.7 and 27.3 wt.% respectively. The increase in sweep flow rate from 15 ml min−1 to 25 ml min−1 enhanced the production of pyrolytic oil yield to 92.6 wt.%. Density functional theory (DFT) was performed to examine the experimental results and distribution of the products involved in the dissociation of RAME. Assuming C−C bond scission followed by the cleavage of the OH bond, the reaction energy of MU and HEP thermal cracking is computed using DFT. This research may provide an alternative pathway to produce important chemicals from castor oil for upscaling and process development for the industry.