IR Pyrometer Research Articles

Effect of tempering on laser remelted AISI H13 tool steel

The effect of tempering temperature on surface hardened AISI H13 tool steel by laser remelting process using an Yb-fiber laser has been investigated. Single remelting tracks were produced in argon environment at different laser power and scan speed in the range of 400–600 W and 200–1600 mm/min respectively, maintaining the laser spot diameter fixed at 3 mm. Their effects on geometrical aspects, microstructure and microhardness were analyzed considering the thermal history of molten pool recorded using an IR pyrometer. Microstructure was found to be associated with cooling rate and melt pool lifetime, estimated from the temperature signal. Thereafter, remelted surface with 30% overlapping tracks was generated and subjected to 1 h tempering cycle at different temperatures in 500–900 °C range followed by hardness and wear tests. Hardness was retained fully up to 500 °C and significant softening occurred at 600 °C and 700 °C. At 800 °C and higher temperatures, effects of laser remelting were impaired completely, but substrate got hardened through martensite formation in a conventional manner. Wear resistance followed the trend of hardness. Changes in microstructure and formation of various phases were found to be the reasons behind the modifications in hardness.

Monitoring and assessment of tungsten carbide wettability in laser cladded metal matrix composite coating using an IR pyrometer

Laser cladding technique was applied to deposit a metal matrix composite coating of Inconel 718 with 30 wt% WC as a ceramic phase. One of the major problems associated with obtaining fully dense MMC coating is the poor wetting/bonding between the ceramic particles and the metal matrix. Further, a large number of process parameters involved in the laser cladding process makes it more complex to optimise the process window. Therefore, the current study focuses on the monitoring of molten pool thermal history which is an outcome of the combination of all process parameters, and identifies the molten pool lifetime and cooling rates that are favourable for the formation of interfacial layer improving the wetting characteristics. The thermal history of molten pool was recorded using an IR pyrometer. The molten pool lifetime, solidification shelf time and cooling rates were assessed from the data acquired and effect of these on wetting characteristics and formation of interfacial layer between WC particles and metal matrix was analysed using SEM analysis. Molten pool lifetime greater than 0.68 s exhibited proper wetting of WC particles with the matrix. Fractured surface of coatings that experienced relatively fast cooling revealed the delaminating of ceramic particles from the metal matrix under the tensile load, whereas in one with slow cooling particles found to stay intact with the metal matrix improving the wear properties of the coating. However, too slow cooling resulted in settlement of WC particles at the bottom of molten pool reducing the wear resistance of the coating.

Online assessment of TiC decomposition in laser cladding of metal matrix composite coating

Decomposition of ceramic particles in metal matrix composite coatings developed by laser cladding process is one of the major problems that deteriorate the mechanical properties of coating. Further, a large number of process parameters involved in laser cladding makes the process optimization difficult. Therefore, a study was undertaken to assess the condition of TiC particles in the molten pool by monitoring the thermal history using an IR pyrometer. It was observed that with the increase of molten pool lifetime, a reaction layer is created between TiC particles and metal matrix which improves their bonding. However, with further increase in the molten pool lifetime TiC particles were found to decompose completely forming dendritic structure in the metal matrix through heterogeneous nucleation and subsequent crystallization during the solidification process. This results in a change of the solidification shelf slope which can be used as an effective signature to assess the TiC particle condition in molten pool online without performing any destructive test. The modified structure of metal matrix exhibited brittle nature which increased the wear rate due to fracture and spalling of coating during the wear test.

Image analysis of speckle patterns as a probe of melting transitions in laser-heated diamond anvil cell experiments.

The precision of melting curve measurements using laser-heated diamond anvil cell (LHDAC) is largely limited by the correct and reliable determination of the onset of melting. We present a novel image analysis of speckle interference patterns in the LHDAC as a way to define quantitative measures which enable an objective determination of the melting transition. Combined with our low-temperature customized IR pyrometer, designed for measurements down to 500 K, our setup allows studying the melting curve of materials with low melting temperatures, with relatively high precision. As an application, the melting curve of Te was measured up to 35 GPa. The results are found to be in good agreement with previous data obtained at pressures up to 10 GPa.

Simulation of IR Heating for Composite Stamping

Composite stamping is a two steps process that includes an infrared heating oven in order to melt the composite sheets before forming. This study deals with the numerical simulation of the heating step of the process. The numerical model has been validated using three woven glass and carbon / PA6.6 composites provided by Solvay Rhodia. This type of simulation consists in solving the heat equation with a radiative flux that characterizes the interaction of the material with the IR heating. The model thus considers the IR properties of the material (emission and reflexion). Considering a homogeneous composite, the optical and thermal properties of sheets have been first measured. The material’s emissivity has been measured using a FTIR spectrometer from the reflective and transmitive spectra, by using the Kirchoff law and considering a Lambertian material. Three complementary measurement techniques were used to determine the thermal properties of the composites. Differential Scanning Calorimetry (DSC) measurements have been performed to identify the heat capacity of the composites. On another hand, a hot disc system (measurements performed at the LTN, France) has been used in transient conditions to determine the heat capacity and the thermal conductivity of the composites is all three directions. Finally, the in-plane thermal matrix of conductivity has also been measured by thermography by using an inverse method. The simulation of composites heating has been performed with Comsol MultiphysicsTM and the simulation procedure was validated by comparison with experimental results. The simulated IR oven is composed of 9 IR emittors provided by Toshiba Lighting Company that emit mainly in short IR wavelength (0.75-2µm). The emission properties of the tungsten filament were implemented in order to simulate the IR heating. Free convective heat transfer was also taken into account in the oven. In order to validate the model, an experimental set-up was instrumented with a calibrated IR pyrometer that measured the back side of the heated composite sheets. The experimental results confirm a low thermal gradient through composite thickness, in particular for carbon-reinforced composite. This result is consistent with the low Biot number of the composites. Moreover, experimental and simulated temperatures are in good agreement with an error lower than 15% in the entire heating stage from room to melt temperature.

Susceptor-assisted microwave annealing for activation of arsenic dopants in silicon

Microwave annealing of arsenic-doped silicon was employed to achieve nearly complete dopant activation and repair of damage caused by ion implantation. Analysis of Rutherford backscattering spectra suggested that volumetric heating from microwaves can repair ion-implantation damage. Secondary ion mass spectroscopy depth profiling revealed that even with high damage due to implanted arsenic, microwave annealing achieves repair of lattice damage, and electrical activation of dopants without allowing any significant dopant diffusion into the silicon substrate. Surface temperatures greater than 700°C were achieved within ~100s with assisted microwave heating, marking this as a quick annealing technique when compared to un-assisted annealing. This temperature was sufficient for solid phase epitaxial growth in Si. The temperature profile recorded by a thermocouple-calibarated IR pyrometer was explained based upon the type of losses the sample undergoes while heating. The mechanism for susceptor-assisted microwave heating was dominated by dipole polarization losses in the initial stages of anneal and by Ohmic conduction losses at higher temperatures. Cross-section transmission electron microscopy, along with ion channeling spectra indicated that the silicon lattice regained nearly all of its crystallinity during the microwave anneal. Hall measurement and sheet resistance characterization were used to assess the extent of dopant activation.

Numerical and experimental study of the thermal stress of silicon induced by a millisecond laser

A spatial axisymmetric finite element model of single-crystal silicon irradiated by a 1064 nm millisecond laser is used to investigate the thermal stress damage induced by a millisecond laser. The transient temperature field and the thermal stress field for 2 ms laser irradiation with a laser fluence of 254 J/cm(2) are obtained. The numerical simulation results indicate that the hoop stresses along the r axis on the front surface are compressive stress within the laser spot and convert to tensile stress outside the laser spot, while the radial stresses along the r axis on the front surface and on the z axis are compressive stress. The temperature of the irradiated center is the highest temperature obtained, yet the stress is not always highest during laser irradiation. At the end of the laser irradiation, the maximal hoop stress is located at r=0.5 mm and the maximal radial stress is located at r=0.76 mm. The temperature measurement experiments are performed by IR pyrometer. The numerical result of the temperature field is consistent with the experimental result. The damage morphologies of silicon under the action of a 254 J/cm(2) laser are inspected by optical microscope. The cracks are observed initiating at r=0.5 mm and extending along the radial direction.

Contactless Monitoring of Shrinkage and Temperature Distribution during Hybrid Microwave Sintering

AbstractA novel method to investigate the microwave hybrid sintering process is presented. The method described measures simultaneously over time the changes in shrinkage and temperature field on the sample's surface. The measurements are carried out continuously by using a CCD camera and an IR pyrometer during microwave heating. Moreover, the equipment used is both contactless and less expensive than conventional approaches.

Efficient preparation of nanocrystalline anatase TiO 2 and V/TiO 2 thin layers using microwave drying and/or microwave calcination technique

This study has demonstrated that the synthesis of TiO 2 and V/TiO 2 thin layers may be significantly improved and extended if microwave energy is employed during the drying and/or calcination step. Thin nanoparticulate titania layers were prepared via the sol–gel method using titanium n-butoxide as a precursor. As prepared films were then analyzed by means of various characterization techniques (Raman spectroscopy, UV/Vis, AFM, XPS) in order to determine their functional properties. The photocatalytic activities of prepared layers were quantified by the decoloring rate of Rhodamine B. All thermal treatments in microwave field were done in the same manner, by using an IR pyrometer in the microwave oven and monitoring the temperature of the heating. Nevertheless the microwave and thermally prepared materials were different. This in turn may lead to differences in their functional and also photocatalytic properties.

Low surface temperature synthesis and characterization of diamond thin films

Polycrystalline diamond films are deposited on p-type Si(100) and n-type SiC(6H) substrates at low surface deposition temperatures of 370–530 °C using a microwave plasma enhanced chemical vapor deposition (MPECVD) system. The surface temperature during deposition is monitored by an IR pyrometer capable of measuring temperature between 250 and 600 °C in a microwave environment. The lower deposition temperature is achieved by using an especially designed cooling stage. The influence of the deposition conditions on the growth rate and structure of the diamond film is investigated. A very high growth rate up to 1.3 μm/h on SiC substrate at 530 °C surface temperature is attributed to an optimized Ar-rich Ar/H 2/CH 4 gas composition, deposition pressure, and microwave power. The structure and microstructure of the films are characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. A detailed stress analysis of the deposited diamond films of grain sizes between 2 and 7 μm showed a net tensile residual stress and predominantly sp 3-bonded carbon in the deposited films.

Fission enhanced diffusion of uranium in zirconia

This paper deals with the comparison between thermal and Fission Enhanced Diffusion (FED) of uranium into zirconia, representative of the inner face of cladding tubes. The experiments under irradiation are performed at the Institut Laue Langevin (ILL) in Grenoble using the Lohengrin spectrometer. A thin 235UO2 layer in direct contact with an oxidised zirconium foil is irradiated in the ILL high flux reactor. The fission product flux is about 1011ionscm−2s−1 and the target temperature is measured by an IR pyrometer. A model is proposed to deduce an apparent uranium diffusion coefficient in zirconia from the energy distribution broadening of two selected fission products. It is found to be equal to 10−15cm2s−1 at 480°C and compared to uranium thermal diffusion data in ZrO2 in the same pressure and temperature conditions. The FED results are analysed in comparison with literature data.

Thermal- and radiation-enhanced diffusion of uranium in oxidised zirconium

This paper is devoted to the study of the defect influence on uranium diffusion in zirconia in the context of nuclear waste disposal. The experiments in reactor conditions are performed at the Institut Laue Langevin in Grenoble using the Lohengrin spectrometer. A thin UO 2 layer in direct contact with a zirconium foil is irradiated in the ILL high-flux reactor. The fission product rate is around 3×10 11 ions s −1 and the neutron flux is equal to 5×10 14 n cm −2 s −1. The target temperature is controlled by an IR pyrometer and ranges from 470 to 490 °C. In these conditions, a zirconium oxidation is first observed before uranium diffusion. A model is proposed to deduce an apparent uranium diffusion coefficient in zirconia (ZrO 2) from the energy distribution broadening of a selected fission product ( A=90). It is found to be equal to 10 −15 cm 2 s −1. The study of thermal diffusion is performed by using ion beam techniques (ion implantation and Rutherford Backscattering). ZrO 2 samples are implanted with 800 keV uranium ions at a dose of 10 16 ions cm −2 and annealed at a pressure of 7.5×10 −1 Pa. No uranium diffusion could be observed up to 800 °C. The influence of irradiation defects mainly due to fission products, both on zirconium oxidation and on uranium diffusion, is clearly demonstrated.

Multispectral precise pyrometer for measurement of seawater surface temperature

The paper presents selected problems referring to remote precise temperature measurements. A method of correction of temperature measurement of seawater, disturbed by sun radiation, and a method of elimination of power supply interference were discussed for multispectral IR pyrometer.

Measurement and modelling of the film casting process: 2. Temperature distribution along draw direction

In the case film process a polymer melt is extruded through a slit die, stretched in air and cooled on a chill roll. During the path in air the melt cools and a reduction of both thickness and width takes place; obviously, temperature distribution, thickness and width reductions are function of draw ratio and stretching distance. Temperature distribution along the draw direction was measured as function of flow rate during film casting experiments performed with an iPP resin. A non-contacting method of measurement, based on a narrow-band IR pyrometer, was adopted. A good qualitative agreement is shown between experimental temperature data and predictions of a model accounting of radiation emissivity dependence upon film thickness. Differences are consistent with discrepancies of film thickness evolution along draw direction, indeed the model slightly over predicts both film thickness reduction and, parallel, temperature decrease along the draw direction.

Microwave Sintering of Pure and Doped Nanocrystalline Alumina Compacts

AbstractA single-mode cavity microwave furnace, operating in the TE103 mode at 2.45 GHz is being used to investigate sintering of pure and doped nanocrystalline alumina. The purpose of these experiments is to determine the effect of additives on the sintering process in the nanocrystalline regime. Using the sol-gel method, high purity Al2O3 nanocrystalline powders were synthesized. These powders were calcined at 700°C and then CIP'ed to 414 MPa, producing 0.4 in. diameter, 0.25 in. high cylindrical compacts. The compacts were heated in the microwave furnace to temperatures between 1100°C to approximately 1800°C and were then brought back to room temperature using a triangular heating profile of about 30 minutes duration. A two-color IR pyrometer was used to monitor the surface temperature of the workpiece. The additives tested in this work lowered the temperature needed for densification but this effect was offset by increased grain growth. Initial grain growth from < 5 nm to ∼ 50 nm was closely correlated with the γ to α-alumina phase transition.

Effect of roughness and sliding speed on the wear and friction of ultra-high molecular weight polyethylene

The friction and wear of ultra-high molecular weight polyethylene (UHMWPE) pins sliding against a stainless steel disc were measured for sliding speeds ranging from 1.25 to 10 m s −1 and disc surface roughnesses R a from 0.07 to 0.53 μm ms −1. Frictional heating was controlled by air jets and surface temperature measured with an IR pyrometer. It was found that the wear of UHMWPE is critically dependent on surface temperature and that, when the temperature exceeds a critical value, wear proceeds in a series of discrete steps caused by the sudden loss of a molten or softened layer of polymer. Wear was also influenced by surface roughness. An optimum surface roughness, i.e. a minimum of wear was found at low and medium sliding speeds. At the highest speed tested, however, the influence of roughness on wear rate was much less distinct. Scanning electron photomicrographs of worn pins and disc surfaces revealed evidence of melting by UHMWPE at high sliding speeds and abrasion at high surface roughnesses. Transfer films on disc surfaces were limited to isolated deposits of polymer wear particles.

High speed scanning calorimetry for amorphous alloys

A high speed scanning calorimeter has been developed for simultaneous measurements of heat capacity and electrical resistivity of thin strips. The system was designed for amorphous alloys but can be used for other materials as well. The specimen is heated by an electrical current at rates ranging from 250 to 40,000 K·s−1, and the temperature is sensed by an IR pyrometer ranging down to room temperature. The maximum data acquisition rate is 50 kHz. Operational characteristics of the system are given, and various phenomena that affect design and operation are discussed. Data are taken for some Metglas alloys. Glass transition and crystallization temperatures as well as rough viscosity data are evaluated. At high heating rates the glass transition is spread over a wide temperature range. The formation of metastable crystalline phases can be bypassed so that stable phases form directly from the amorphous state.

Infrared temperatures of coal dust explosions

A comprehensive set of temperature measurements is presented for coal dust explosions as a function of dust concentration. Data include the dependence of explosion temperature on particle size, volatility, oxygen content, and added rock dust. The majority of the data are for constant volume explosions in a laboratory-scale vessel, but data from a coal dust burner flame and full-scale mine dust explosions are also included. In all of the measurements, the gas temperature was significantly higher than the dust particle temperature. The measurements were made with a three-wavelength near-ir pyrometer and a six-wavelength ir pyrometer (in the 1–5-μm-wavelength region). Some thermocouple measurements are shown for comparison.

Temperature fields during sapphire crystal growth

The theoretical aspects of pyrometry of semitransparent materials are considered. An IR pyrometer for measuring the sapphire and ruby surface temperature has been developed. This technique allows one to investigate the temperature fields ( T fields) when growing sapphire crystals by the horizontal uniaxial crystallization method (HUC). The influence of the construction elements and heat exchange conditions on the T fields has been investigated. It has been shown that in a HUC apparatus the temperature gradient (grad T) reaches a maximum at a distance of ∼30 mm from the growth interface. Variations in T field and grad T during growth processes have been investigated. Experimental data on the supercooling limit of sapphire have been obtained.