Torch Heating Research Articles

Modelling and Experimental Validation of the Flame Temperature Profile in Atmospheric Plasma Coating Processes on the Substrate

This work presents a characterisation model for the temperature distribution at different substrate depths during the atmospheric plasma spray (APS) coating process. The torch heat flow in this model is simulated as forced convection defined by a surface, a temperature profile, and a convection coefficient. The simulation model considers three plasma temperature profiles of the Al2O3 coating on a 5 mm thickness flat aluminium substrate. The simple and low-cost experimental procedure, based on a thermocouple, measures the plasma plume temperature distribution of the APS coating system, and their results are used to obtain the parameter values of each of the three proposed plasma temperature profiles. The experimental method for in situ non-contact temperature measurements inside the substrate is based on an infrared pyrometry technique and validates the simulation results. The Gaussian temperature profile shows excellent accuracy with the measured temperatures. The Gaussian approach could be a powerful tool for predicting residual stress through a coupled one-way thermal-mechanical analysis of the APS process.

Heat treatments for thermal sprayed lead-free piezoelectric ceramic coatings

[0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3]0.98-(LiNbO3)0.02 (BNBTLN) piezoelectric ceramic coating was fabricated by thermal spray process on stainless steel substrates with thermal barrier coating (TBC) as an intermediary layer. The morphology, structure, and electrical properties of the thermal-sprayed BNBTLN coatings after furnace heat treatment (F-HT) and plasma torch heat treatment (P-HT) were studied, respectively. The BNBTLN coatings after F-HT and P-HT both had the coexisting rhombohedral and tetragonal perovskite phases and exhibited excellent electrical properties, with an effective piezoelectric coefficient d33 of 68 p.m./V and 40 p.m./V, respectively. These results reveal that high quality piezoelectric coatings can be achieved by the P-HT method, which is promising for scaling up the fabrication of piezoelectric ceramic coatings.

Utilizing torch-substrate relative velocity to reduce segmentation crack density in plasma sprayed zirconia for solid oxide cell applications

Torch-substrate relative velocity is a plasma spray coating control parameter that affects lamellar thickness, heat transfer from the torch to the substrate, splat dispersion, and segmentation crack density. Within the thermal barrier coating and solid oxide fuel cell/solid oxide electrolysis literature, plasma sprayed coatings are rarely fabricated with velocities that exceed ∼2 m s−1. Here, we explore the effect of torch-substrate relative velocities in the range of 4–20 m s−1 on crack density in thin (10–15 μm) solid oxide cell electrolyte coatings. Crack densities were observed to drop from ∼2.4 to ∼0.04 mm−1 by increasing the torch-substrate relative velocity from 4 to 16 m s−1. In agreement with previous studies performed at lower velocities, crack densities correlate well with plasma torch heat impulse. Full cells were fabricated using torch-substrate relative velocities of 12–20 m s−1.

The impact of technological parameters of the torch to physical and chemical properties of a gas-thermal burner for spraying ultra-high molecular weight polyethylene

The values of the heat flux density, transverse and longitudinal temperature gradients of the gas-thermal burner torch, the type of reaction during the combustion in various modes (reducing, neutral, oxidizing) depending on the mass fractions of the fuel and oxidizer burning have been determined in this paper. The significant role of the torch temperature as one of the most important parameters determining the quality of polymer coatings obtained by the gas-thermal method has been established. A spatial model of a gas-thermal burner has been designed, which allows to obtain thermal modes at specified technological parameters. A physical model of the interactions “torch-polymer particle”, “thermal jet – base” has been developed. The necessary density of the torch heat flux for the complete melting of ultrahigh molecular weight polyethylene (UHMWPE) particles not exceeding the temperature threshold of destruction has been determined. The required rate of introduction the UHMWPE powders into the burner flame has been also determined. Based on the calculations of the “torch-polymer particle interaction”, the optimal geometry of the torch, the particles trajectory in the torch and the spraying distances have been determined.

Modelling the effect of hot gas torch heating on adjacent tows during automated fibre placement consolidation of thermoplastic composites

Many numerical models of the Automated Fibre Placement (AFP) manufacturing process have been developed to assist in the design process of composite components and structures. Although the tape placement process, in general is a 3-D transient process, limited models considering the 3-D nature of the process exist. This paper describes the development of a 3-D Finite Element (FE) model incorporating the effect of non-concentrated input heat flux distribution on adjacent paths. The model can predict an accurate thermal history of a thermoplastic composite laminate for a complete AFP deposition process. Composite laminates having plies made up of both a single tow and multiple tows have been simulated to study their thermal behaviour during the manufacturing process. Simulations have been conducted both with and without considering the input heat effect on adjacent tows for comparison. Temperatures were measured by embedding two different configurations of optical fibre Bragg grating (FBGs) sensors within the laminate during the lay-up process. This served a dual purpose of validating the model as well as the experimental methodology.

Synthetization of TiC surface hardening using TIG melting technique - The effect of working distance

Surface hardening with and without hard reinforcing material can be achieved by melting technique on the top substrate area via high energy input fusion. The aim is to apply TIG torch heat input of 1344 J/mm at two different working distances such as 0.5 mm and 1.5 mm to incorporate the preplaced TiC particulates on the surface of AISI 4340 low alloy steel. Results pertaining to the microstructural features, melt pool sizes, defects, topographies and microhardness were investigated using the optical microscope, scanning electron microscope and Vickers microhardness tester. The results showed that the heat loss through the arc column at 1.5 mm of working distance resulted small melt pool geometry and poor dissolution of TiC particulates. Lower working distance increases heating value leading more precipitation of TiC whilst minimizing those the undissolved particulates. The surface submerged at working distance of 0.5 mm produced microhardness ranging from 800 HV to 1500 HV. The work suggested that heat fusion can be enhanced by marginal working distance whilst saving the energy to melt instead of increasing the used voltage, current, decreasing scanning speed, or adding fluxes or shielding with special gasses.

Quaternary Artificial Nacre-Based Electronic Textiles with Enhanced Mechanical and Flame-Retardant Performance

Interest in wearable electronics has led to extensive studies on woven textiles that are mechanically robust and stretchable, have high electrical conductivities, and exhibit fire resistance properties even at high temperatures. We demonstrate a highly easy and scalable method for fabricating defect-free graphene (dfG) nacre-based woven electronic textiles (e-textiles) with enhanced flame-retardant properties and high electronic conductivities. The as-prepared graphene shows perfect preservation of its inherent properties without any crystal damage during subsequent exfoliation and noncovalent melamine functionalization. The defect-free graphene functionalized by melamine (m-dfG) is well dispersed in various polar solvents. To investigate the synergistic effect of m-dfG, quaternary artificial nacre composites are fabricated by adding manganese(II) chloride to a m-dfG/polymer (carboxymethyl cellulose (CMC)) composite. Their mechanical, electrical, and thermal characteristics are then evaluated. The quaternary m-dfG-Mn2+-CMC artificial nacre exhibits exceptionally enhanced mechanical properties (tensile strength: 613.9 MPa; toughness: 7.13 MJ m-3) and the best flame retardancy (even at torch heating) as compared to those of graphene oxide/reduced graphene oxide (GO/rGO)-based nacres. In this context, our approach will be helpful to future wearable electronics and fire-retardant textiles with high strength, which can accelerate the commercial viability of e-textiles.

A Facile and Rapid Fabrication of Multifunctional Color-Tuned Titanium

In this article, a strategy for the fabrication of color-tuned titanium using a torch was developed. The torch was used to manufacture a layer of titanium dioxide on titanium substrates. The reaction time and requirements were reduced compared to the anodization process. Various colors appeared depending on the time of torch heating, and this torched-titanium substrate was treated with octadecyltriethoxylsilane (ODTS) to gain superhydrophobic properties for self-cleaning. Scanning Electron Microscope (SEM), Raman spectroscopy, and Atomic Force Microscope (AFM) were used for surface analysis. Besides, the mechanical and ODTS stability of the surface were evaluated through a cross-cut adhesion tape test and water contact angle measurement, proving that the torch is a suitable fabrication process for multifunctional color-tuned titanium.

Calculations of Heat Transfer in Combustion Chambers of Gas Turbine Plants According to the Laws of Thermal Radiation of Gas volumes

The analysis of methods for calculating heat transfer in the combustion chambers of gas turbine plants is carried out. None of the existing methods for calculating heat transfer gives a complete and accurate picture of heat transfer in combustion chambers. The calculation method developed on the basis of scientific discovery allows one to calculate with high accuracy the density of the torch heat fluxes along the surfaces of the flame tube, organize rational heat transfer in the combustion chamber, reduce costs and time of creation of combustion chambers and increase their service life.

Ablation Behaviour and Microstructure of Carbon/Carbon and Hybrid Carbon/Carbon Composites Based on Plasma Torch Heating

The ablation properties and morphologies of two kinds of fine Fine-woven pierced composites materials, carbon/carbon (C/C) and hybrid C/C with tungsten (W) filaments in z directional carbon fibre bundles, were investigated. A plasma torch was used to explore the ablative characteristics in terms of linear/bulk ablation rate and microscopic pattern of ablation. Surface and in-depth temperatures during ablation were measured by using optical pyrometers and thermocouples. The experimental results showed that the C/C composite presented the best ablation resistance performance, followed by the hybrid C/C composite, while that of graphite was the worst. It was found that the thermo-mechanical ablation resistance of carbon matrix is equal to that of carbon fibres. The existence of WC not only had a faster intrinsic ablation velocity, but also accelerated the ablation velocity of the carbon fibres and carbon matrix, and significantly improved the ablation velocity of the carbon fibres.

V-groove를 가진 모재에서 코일 형상에 따른 유도가열 해석

In order to prevent crack in thick weld zones, the preheating process such as induction and gas torch heating needs to be applied. Among them induction heating is the most effective heat source because it has rare thermal effect and very rapid heating characteristics. In this paper, when the induction heating method is used to improve arc welding, the temperature distribution and magnetic field density of the welding zones are analyzed by simultaneously solving heat transfer and electromagnetic field equation. In particular, cone and flat type coils are designed and induction heating effects of each type are compared to identify heating characteristics on a V ?groove weld joint. As a result, a cone shape coil is more efficient in the preheating process. When induction heating and arc welding system is designed for thick plate with V-groove weld joint, the results in this paper could be applied.

Laws of Heat Radiation from Surfaces and Gas Volumes

It is proven that the law of radiation from solid bodies, Stefan-Boltzmann law shall not be used to calculate heat radiation from gas volumes which are formed in fuel flaring. The determining influence on heat fluxes density of the torch to the heating surfaces has not only a temperature, but power, dimensions, geometrical position of radiative gas volumes. The laws of radiation from gas volumes disclosed in 2001 and the method for calculating heating fluxes from gas volumes, developed on its basis, which takes into account the radiation from full set of particles in gas volume are stated. The torch model in the form of radiative gas volume is used to calculate heat transfer in torch heating furnaces, steam boiler boxes, turbogas unit combustors. The disclosure has enabled us to create new furnaces, fire boxes, combustion chambers, enhance unit performance, and decrease fuel rate, pollutant emissions.

Ablation Performances of Multi-phased C/C-ZrC-SiC Ultra-high Temperature Composite

The 2D C/C-ZrC-SiC composites were prepared through precursor infiltration and pyrolysis (PIP) process using a hybrid precursor contained polycarbosilane and organic zirconium-contained polymeric precursor. The microstructures and ablation behaviors of the prepared composites were studied. The composition and microstructure of the ablated samples were characterized by XRD and SEM, respectively. The results show that the mass ablation rate and linear ablation rate of the composites generally firstly decrease and then increase with the increasing of ZrC contents. The sample with 17.45vol% ZrC has optimum anti-ablation property. After ablation at 2200 degrees C for 300s via the plasma torch heating technique, the mass loss and linear recession rate is as low as 1.77mg/s and 0.55 mu m/s, respectively. It is found that during ultra-high temperature stage, the matrix of ZrC and SiC are oxidized into ZrO2 and SiO2, which form a kind of viscous binary glassy mixture. The mixture could effectively cover the ablation surface and therefore promote its anti-ablation property.

탄소강 환봉의 레이저 표면변태경화 특성에 관한 연구 (I) - 가우시안 파워밀도 분포의 레이저 열원을 이용한 표면변태경화 특성 -

Laser Material Processing has been replaced the conventional machining systems - cutting, drilling, welding and surface modification and so on. Especially, LTH(Laser Transformation Hardening) process is one branch of the laser surface modification process. Conventionally, some techniques like a gas carburizing and nitriding as well as induction and torch heating have been used to harden the carbon steels. But these methods not only request post-machining resulted from a deformation but also have complex processing procedures. Besides, LTH process has some merits as : 1. It is easy to control the case depth because of output(laser power) adjustability. 2. It is able to harden the localized and complicated a.ea and minimize a deformation due to a unique property of a localized heat source. 3. An additional cooling medium is not required due to self quenching. 4. A prominent hardening results can be obtained. This study is related to the surface hardening of the rod-shaped carbon steel applied to the lathe based complex processing mechanism, a basic behavior of surface hardening, hardness distribution and structural characteristics in the hardened zone.

Modeling of spherulitic crystallization in thermoplastic tow-placement process: spherulitic microstructure evolution

A numerical study on the evolution of spherulitic microstructures during crystallization of fiber-reinforced thermoplastic matrix, poly-ether-ether-ketone (PEEK), in a composite tow-placement process is presented. A model for spherulitic microstructure growth within a unit cell formed between adjacent fibers and at the interlayer surface is developed, by accounting for the spatial temperature variation and the temperature history resulting from hot gas torch heating during the process, as discussed in a previous work [Compos. Sci. Tech., in press]. Parametric studies are conducted to elucidate the effects of processing conditions, in terms of torch incidence angle, θ, torch exit diameter, D, torch distance to target, L, hot gas temperature, T noz, gas velocity, U noz, line speed, V, and number of layers in tow substrate, N layer, on the crystalline microstructures. The range of average spherulite size corresponding to optimal processing conditions based on considerations of overall crystallinity is determined.

Modeling of spherulitic crystallization in thermoplastic tow-placement process: heat transfer analysis

An impingement heat transfer analysis is presented for hot gas torch heating in a tow-placement process of thermoplastic matrix composites. It is shown that experimentally available convective heat transfer correlations for normal and oblique impingement can be adapted to the geometry specific to the process by following first principles. Parametric studies are conducted using a coupled heat transfer and crystallization kinetics model for fabrication of a fiber-reinforced poly-ether–ether–ketone composite. Effects of processing parameters, in terms of torch incidence angle, θ, torch exit diameter, D, torch distance to target, L, hot gas temperature, T noz, gas velocity, U noz, line speed, V, and number of layers in tow substrate, N layer, on the crystallinity development in product are elucidated. Based on an optimal level of crystallinity, a processing window is identified by determining minimum and sonic gas velocities at various gas temperatures and line speeds.

Conjugate heat transfer and particle deposition in the modified chemical vapor deposition process: Effects of torch speed and solid layer

A study has been carried out for the conjugate heat transfer and particle deposition that occur during the modified chemical vapor deposition (MCVD) process. The analysis includes thermophoretic particle transport in the gas flow and heat transfer through the solid layer; the effects of variable properties in both the gas and the solid regions are included. A notable feature of the study is the inclusion of the effects of periodic heating due to the repeated traversing of the torch and the effects of the increasing solid layer thickness as the particles deposit. A new concept uses a two torch formulation to simulate the torch heating from both the present and the previous passes. This formulation is able to predict the minimum wall temperature in front of the torch, which is closely related to the deposition efficiency. Localized heating of the moving torch is studied using the heat flux boundary condition on the tube wall. The calculated surface temperature distribution and the deposition efficiency are in good agreement with experimental data. Of particular interest are the effects of torch speed and solid layer thickness on the efficiency, the rate of deposition of the particles and the taper length.

An analysis of the effect of the solid layer for the modified chemical vapor deposition process

The heat transfer problem relative to the modified chemical vapor deposition process has been analyzed and the effects of solid layer thickness, torch speed and tube rotation are studied. The quasi-steady three-dimensional energy equations have been solved for the temperature fields in the gas and the solid layer with a Gaussian heat flux boundary condition on the outer surface. Of particular interest is the effect of the solid layer thickness and the torch speed on inner surface temperature, gas temperature and thermophoretic velocity. The large change of the axial temperature distribution of the surface occurs for different solid layer thicknesses or torch speeds. The presence of the solid layer and tube rotation reduce the effects of nonuniform torch heating in the circumferential direction and the resulting surface temperatures are very uniform in this direction.

A Study of Heat Transfer and Particle Motion Relative to the Modified Chemical Vapor Deposition Process

Heat transfer and particle motion relative to the modified chemical vapor deposition process have been studied for general values of the torch speed. Three-dimensional temperature fields have been obtained over the entire cross section of the tube and the effects of tube rotation and localized torch heating in the axial and circumferential directions have been studied. The particle trajectories have been calculated from a formulation that includes the contributions from forced flow, i.e, Poiseuille flow in the axial direction, rigid body rotation about the tube axis, and thermophoretic contributions in the axial, radial, and angular directions. The particle trajectories are helices and are shown to be strongly dependent on the tube rotation.

Recent topics of flaw prevention

Flaws resulting from corrosion are still a significant issue in nuclear power plants. Prevention of these flaws is one of the biggest themes of plant maintenance and new countermeasures have been developed year by year. In this paper three newly proposed techniques are presented: (1) ceramics coatings on flange seal surface by surface hardening due to laser-alloying to prevent pitting corrosion; (2) Induction Heating Stress Improvement (IHSI) on nozzle safe-end with thermal sleeve by using forced cooling; and (3) TIG Torch Heating Stress Improvement (THSI) to reduce welding residual stress on small diameter pipes.