Impact Temperature in Splat and Splat-Substrate Interface in HVOF Thermal Spraying
— An explicit axisymmetrical FE methodology is developed here to study the particle temperature arising in WC-Co particle on an AISI 1045 steel substrate. Parameters of constitutive Johnson-cook model were used for simulation. The results show that particle velocity and kinetic energy have important role in temperature arising of particles.
Effect of particle impact on residual stress development in HVOF sprayed coatings
The application of thick high-velocity oxyfuel (HVOF) coatings on metallic parts has been widely accepted as a solution to improve their wear properties. The adherence of these coatings to the substrate is strongly influenced by the residual stresses generated during the coating deposition process. In an HVOF spraying process, due to the relatively low processing temperature, significant peening stresses are generated during impact of molten and semimolten particles on the substrate. At present, finite-element (FE) models of residual stress generation for the HVOF process are not available due to the increased complexities in modeling the stresses generated due to the particle impact. In this work, an explicit FE analysis is carried out to study the effect of molten particle impingement using deposition of an HVOF sprayed copper coating on a copper substrate as an example system. The results from the analysis are subsequently used in a thermomechanical FE model to allow the development of the residual stresses in these coatings to be modeled.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.