Effect Of Post Heat Treatment Research Articles

Microstructure and anisotropic mechanical properties of EBM manufactured Inconel 718 and effects of post heat treatments

Materials manufactured with electron beam melting (EBM) have different microstructures and properties to those manufactured using conventional manufacturing methods. A detailed study of the microstructures and mechanical properties of Inconel 718 manufactured with EBM was performed in both as-manufactured and heat-treated conditions. Different scanning strategies resulted in different microstructures: contour scanning led to heterogeneous grain morphologies and weak texture, while hatch scanning resulted in predominantly columnar grains and strong 〈001〉// building direction texture. Precipitates in the as-manufactured condition included γ′, γ″, δ, TiN and NbC, among which considerable amounts of γ″ yielded relatively high hardness and strength. Strong texture, directionally aligned pores and columnar grains can lead to anisotropic mechanical properties when loaded in different directions. Heat treatments increased the strength and led to different δ precipitation behaviours depending on the solution temperatures, but did not remove the anisotropy. Ductility seemed to be not significantly affected by heat treatment, but instead by the NbC and defects inherited from manufacturing. The study thereby might provide the potential processing windows to tailor the microstructure and mechanical properties of EBM IN718.

The Effect of Post-Heat Treatment in MDF Panels

This study was to evaluate the effect of post-heat treatment on the physical and mechanical properties of MDF (Medium Density Fiberboard) panels. Commercial MDF panels were produced in Brazil using Pinus wood and urea-formaldehyde (UF) adhesive. The post-heat treatments were carried in a factorial 3 x 2 (three temperatures of heat treatment - 200, 225 and 250 °C, and two times - 5 and 10 minutes), and a control treatment (without heat treatment). Subsequently, the physical and mechanical tests were performed. From the results it can be concluded that: 1) The most effective thermal post-treatment for improving the dimensional stability of the MDF was applied at 225 ° C and 10 min; 2) All the thermally treated panels revealed a significant decrease in the modulus of rupture and modulus of elasticity (MOR and MOE) to bending when compared with the control panels without post-heat treatment.

Effect of post-heat treatment on the photocatalytic activity of titanium dioxide nanowire membranes deposited on a Ti substrate

Titanium dioxide nanowire membranes have been synthesized by a hydrothermal growth on the surfaces of Ti substrates in a 12 M NaOH aqueous solution at 160 °C for 24 h, followed by ion-exchange with 0.5 M HCl aqueous solution and subsequent heat treatment.

Paving the Thermal Highway with Self-Organized Nanocrystals in Transparent Polymer Composites.

Phonon transfer is greatly scattered in traditional polymer composites due to the unpaired phonon frequency at the polymer/filler interface. A key innovation of this work is to build continuous crystal network by self-organization and utilize it as "thermal highway" that circumvents the long-existing interfacial thermal barrier issue in traditional composites. By tuning the molecular diffusion rate of dicarboxylic acids (oxalic acid, malonic acid, and succinic acid), different crystal structures including skeletal, dendrite, diffusion-limited aggregates, and spherulite were synthesized in PVA film. These continuous crystal structures benefit the efficient phonon transfer in the composites with minimized interfacial scattering and lead to a significant thermal conductivity enhancement of up to 180% compared to that of pure polymer. Moreover, the transparent feature of these composite films provides additional benefits in display applications. The post heat treatment effect on the thermal conductivity of the composite films shows a time-dependent behavior. These uniquely structured polymer/crystal composites are expected to generate significant impacts in thermal management applications.

Facile synthesis of platinum alloy electrocatalyst via aluminum reducing agent and the effect of post heat treatment for oxygen reduction reaction

We have synthesized carbon-supported Pt and PtM (Au, Pd) nanoparticles (NPs) by using an aluminum (Al) metal foil as a reducing agent and conducted post heat treatments to investigate the relationship between oxygen reduction reaction (ORR) activity and surface crystalline/electronic structures of electrocatalysts. The as-prepared Pt and PtM (Au, Pd) NPs received the post heat treatment to induce structural modifications to improve ORR activity. From structural characterizations, well-synthesized carbon-supported Pt and PtM (Au, Pd) NPs were confirmed and the post heat treatment has the effect of inducing the alteration of surface crystalline structure and results in higher ORR activity. Furthermore, based on electrochemical characterizations, it is proved that after the heat treatment, the surface reconstruction brought about the increased fraction of Pt (111) and electrochemical active surface area of PtAu/C CO sample. And, the downshift of Pt d-band center of PtPd/C CO sample, which decreases the affinity of Pt to oxygen species, occurred resulting in more favorable kinetics of ORR.

The Effect of Post-Heat Treatment on Microstructure of 316L Cold-Sprayed Coatings and Their Corrosion Performance

The combined effects of process gases and post-heat treatment temperature on the microstructure of 316L cold-sprayed coatings on Al5052 substrates have been investigated in this study. The stainless steel coatings were subjected to heat treatment at four different temperatures (250, 500, 750, and 1000 °C) to study the effect of heat treatment. In addition, the corrosion performances of the coatings at different process temperatures have been compared using the potentiodynamic scanning technique. Microstructural characterization of the coatings was carried out using scanning and transmission electron microscopy and x-ray diffraction. The results of present study showed that cold-sprayed stainless steel coatings processed with helium exhibited higher corrosion resistance than those of coatings sprayed with nitrogen process gas. This could partially be attributed to the reduction in porosity level (4.9%) and improvement of particle-particle bonding. In addition, evaluation of the mechanical and microstructural properties of the coatings demonstrated that subsequent heat treatment has major influence on the deposited layers sprayed with He process gas.

Effect of Heat Treatment on Microstructures and Mechanical Properties of Severe Plastically Deformed Hypo- and Hyper-Eutectoid Steels by Caliber Rolling Process

This study investigated the effect of post-heat treatment on the microstructures and mechanical properties of severe plastically deformed hypo- and hyper-eutectoid steels that underwent a caliber rolling process. First, 28 passes of caliber rolling were performed on both the hypo-eutectoid steel with Fe-0.47% C (wt%) composition and the hyper-eutectoid steel with Fe-1.02%C (wt%) composition. Then, the caliber rolled materials underwent heat treatment at 500 degrees C for 1, 3, 5, 10, 30 and 60 minutes. The caliber rolled steel possessed a 300-400 nm-sized oval cementite structure created through elongating and segmentation regardless of the C composition. The observation of heat-treated microstructures showed that cementite structure became globular and ferrite size increased as heat treatment temperature increased. In the hardness measurement, the initial caliber rolled samples showed 372.8 Hv (hypoeutectoid) and 480.1 Hv (hyper-eutectoid). However, hardness dramatically decreased up to 10 min. heat treatments, and then showed a constant or small reduction with time. The yield strengths (compression) of caliber rolled hypo- and hypereutectoid steels obtained were 1097 MPa and 1426 MPa, respectively, and the yield strengths of the same steels after heat treatment (500 degrees C, 60 min.) were identified to be 868 MPa and 1316 MPa, respectively.

Determination of Optimum Post Weld Heat Treatment Processes on the Microstructure and Mechanical Properties of IS2062 Steel Weldments

This study investigates the effect of post heat treatment on the microstructure and mechanical properties of IS2062 steels. Similar metal joints of IS2062 weldments are prepared by using MIG welding process. This melting is occurring at edges of the plates because of sufficient amount of heat energy is passing over the plate per unit time and density of energy is supplied to the wire. In this connection, heating and cooling of weldment some of the disturbances in metallurgical and mechanical point of view. To overcome we will choose suitable post weld heat treatment to avoid the disturbances and improve industrial requirement irrespective of the mechanical, microstructure of the weldment. The objective is to determine the optimum post weld heat treatment method for the IS2062 steel. After welding, the effects of post weld heat treatment on weld metal microstructure and mechanical properties including weldment tensile strength, impact and hardness over the room temperature range 32°C are investigated. In particular this study the effect of these properties to understand estimate heat treatments on the tensile impact, Hardness materials are considered as weldments before heat treatment and after post weld heat treatment.

The Effect of Post-heat Treatment on the Microstructures of Single Crystal DD6 Superalloy

AbstractVarious thermal cycles at the end of solution heat treatment and their influences on microstructure of single crystal superalloy DD6 were studied by experiments. During various thermal cycles, the qualitative and quantitative microstructure of samples quenched of the transformations is microscopically characterized. This completely includes the large changes in volume fraction, size distribution and morphology of gamma prime precipitate experienced in the upper temperature transformation. Noticeable deviation from the equilibrium volume fraction of γ’ phase is detected in both the dissolution and precipitation processes above 1,120°C for both moderate cooling and heating rate; differences were mainly attributed to the unsteady nature of the turbulent flow. The growth and alignment of the γ’ precipitates are deeply influenced by several factors, e.g. ageing time, cooling rate and quenching temperature. In addition, interesting findings such as “labyrinth” and “cluster” morphologies were observed by scanning electron microscope. During precipitation processes, the complicated microstructure evolution is illustrated by considering the consecutive equilibrium shapes of a coherent precipitate, which grows under the interaction with its neighbors and the coherency of the precipitates improves their potential to resist dissolution.

Seeded Porous Silicon Preparation as a Substrate in the Growth of ZnO Nanostructures

In this work, seeded porous silicon (PSi) was used as a substrate in the growth of ZnO nanostructures. PSi was prepared by electrochemical etching method. ZnO thin films as seeded were deposited via sol-gel spin coating method. ZnO nanostructures were grown on seeded PSi using hydrothermal immersion method. In order to study the effect of post-heat treatment on the substrate, post annealing temperature were varied in the range of 300 to 700 °C. The FESEM results shows ZnO thin film composed of nanoparticles were distributed over the PSi surface. Based on AFM characterization, the smoothest surface was produced at post annealing temperature of 500 °C. There are two different peaks appeared in PL characterization. The peak in near-UV range is belonging to ZnO thin films while a broad peak in visible range can be attributed to ZnO defects and PSi surface. In addition, FESEM, XRD and PL were used to characterize the ZnO nanostructures. The FESEM results revealed ZnO nano-flower were successfully grown on seeded PSi. Hexagonal wurtzite of ZnO with dominated by the plane (100), (002), and (101) was found by XRD characterization. Two different peaks in UV range and visible range can be attributed to ZnO nano-flower and various defects of ZnO, respectively.

Effect of Post-Heat Treatment on the Critical Current Density of Nb3Al Superconductor

The achievement of stoichiometry is very important for Nb3Al superconductor with excellent properties. A rapid heating, quenching, and transformation method is efficient to achieve stoichiometric Nb3Al superconducting wires, and supersaturated solid solution phase was transformed to Nb3Al in the transformation process with a post-annealing temperature between 800° to 900 °C and for 10 h. X-ray diffraction analysis revealed that the Nb3Al wires were of pure Nb3Al phase with a superconducting transition temperature about 18 K. Experimental results further showed that superconducting transition width was narrowed by quenching process after post-annealing. For the typical samples, the Hc2(T) was determined from the onset transitions of the M–Tcurves under various applied fields and the Hc2(0) value was extrapolated to be about 35 T. A significantly high Jc value under a magnetic field up to 9 T and at 8 K was observed. The pinning behavior of the Nb3Al wires was also discussed.

Effects of high temperature treatment on microstructure and mechanical properties of laser-clad NiCrBSi/WC coatings on titanium alloy substrate

Laser-clad composite coatings on the Ti6Al4V substrate were heat-treated at 700, 800, and 900°C for 1h. The effects of post-heat treatment on the microstructure, microhardness, and fracture toughness of the coatings were investigated by scanning electron microscopy, X-ray diffractometry, energy dispersive spectroscopy, and optical microscopy. The wear resistance of the coatings was evaluated under dry reciprocating sliding friction at room temperature. The coatings mainly comprised some coarse gray blocky (W,Ti)C particles accompanied by the fine white WC particles, a large number of black TiC cellular/dendrites, and the matrix composed of NiTi and Ni3Ti; some unknown rich Ni- and Ti-rich particles with sizes ranging from 10nm to 50nm were precipitated and uniformly distributed in the Ni3Ti phase to form a thin granular layer after heat treatment at 700°C. The granular layer spread from the edge toward the center of the Ni3Ti phase with increasing temperature. A large number of fine equiaxed Cr23C6 particles with 0.2–0.5μm sizes were observed around the edges of the NiTi supersaturated solid solution when the temperature was further increased to 900°C. The microhardness and fracture toughness of the coatings were improved with increased temperature due to the dispersion-strengthening effect of the precipitates. Dominant wear mechanisms for all the coatings included abrasive and delamination wear. The post-heat treatment not only reduced wear volume and friction coefficient, but also decreased cracking susceptibility during sliding friction. Comparatively speaking, the heat-treated coating at 900°C presented the most excellent wear resistance.

Effects of post-heat treatment on microstructure and properties of laser cladded composite coatings on titanium alloy substrate

The composite coatings were produced on the Ti6Al4V alloy substrate by laser cladding. Subsequently, the coatings were heated at 500 °C for 1 h and 2 h and then cooled in air. Effects of post-heat treatment on microstructure, microhardness and fracture toughness of the coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), optical microscopy (OM). Wear resistance of the coatings was evaluated under the dry sliding reciprocating friction condition at room temperature. The results indicated that the coatings mainly consist of a certain amount of coarse white equiaxed WC particles surrounded by the white-bright W2C, a great deal of fine dark spherical TiC particles and the matrix composed of the α(Ti), Ti2Ni and TiNi phases. Effects of the post-heat treatment on phase constituents and microstructure of the coatings were almost negligible due to the low temperature. However, the post-heat treatment could decrease the residual stress and increase fracture toughness of the coatings, and fracture toughness of the coatings was improved from 2.77 MPa m1/2 to 3.80 MPa m1/2 and 4.43 MPa m1/2 with the heat treatment for 1 h and 2 h, respectively. The mutual role would contribute to the reduction in cracking susceptibility. Accompanied with the increase in fracture toughness, microhardness of the coatings was reduced slightly. The dominant wear mechanism for all the coatings was abrasive wear, characterized by micro-cutting or micro-plowing. The heat treatment could significantly decrease the average friction coefficient and reduce the fluctuation of the friction coefficient with the change in sliding time. The appropriate heat treatment time (approximately 1 h) had a minimal effect on wear mass loss and volume loss. Moreover, the improvement in fracture toughness will also be beneficial to wear resistance of the coatings under the long service.

코발트기 자융성합금 코팅의 마모특성에 미치는 후열처리의 영향

Abstract: This article describes effect of post heat treatment on wear characteristics of thermally sprayed Co-based self-flux alloy coating. Co-based self-flux alloy coatings were deposited on steel substrates using a flame spray process. Post heat treatments were carried out at 800, 900, 1000 and 1100℃ for 30min in a vacuum chamber. For analysis of effect of post heat treatment on mechanical properties, wear test and hardness test were performed for post heat-treated coating specimen. Microstructures of heat treated coating layer and wear track were examined using SEM and EDS. Wear loss and hardness became lower with increasing post heat treatment temperature. Key Words ： Co-based Self-flux Coating, Post Heat Treatment, Microstructure, Wear Microhardness **†김영식(교신저자) : 부경대학교 기계자동차공학과E-mail : Yeongsik@pknu.ac.kr, Tel : 051-629-6155 *이재홍 : 부경대학교 대학원**†Yeong-Sik Kim(corresponding author) : Department of Mechanical & Automotive Engineering, Pukyong National UniversityE-mail : Yeongsik@pknu.ac.kr, Tel : 051-629-6155*Jae-Hong Lee : Graduate School, Pukyong National University

Effects of post heat treatment on near infrared photoluminescence of YAG:Yb3+ nanoparticles synthesized by glycothermal method

Influence of post heat treatment on particulate, structural, surface, and optical properties of YAG:Yb3+ nanoparticles prepared by glycothermal method is studied to understand factors for determining photoluminescence intensity. Characterization is performed on electron microscopy, X-ray diffractometry, infrared absorption spectroscopy, and optical measurements. Near infrared emission under 940nm near infrared excitation is observed at 1029nm corresponding to 2F5/2→2F7/2 transition of Yb3+. Subsequent heat treatment causes crystallite growth and elimination of hydroxyl groups, resulting in an enhancement of the near infrared emission.

Post Heat Treatment Effect on Electrochemically Synthesized CuO Thin Films

We have investigated the post heat treatment effect of electrochemically prepared cupric oxide (CuO) thin films. The films were annealed at different temperatures ranging from 200 to 400°C in air medium. The annealed films structural, optical, compositional and morphological properties were studied. X-ray diffraction patterns show that as-deposited film exhibited cubic structure with preferential orientation along the (111) plane. Annealing was induced further grain growth and tightened the grain size distribution. The morphological properties and surface roughness were studied using scanning electron microscopy and atomic force microscopy. Optical properties of the films were analyzed by recording transmission, absorption and reflection spectra. Optical band gap of as-deposited and annealed CuO thin films were estimated by conventional method.

Effect of post heat treatment on thermal durability of thermal barrier coatings in thermal fatigue tests

The effects of post heat treatment and coating parameters on the microstructural development of thermal barrier coatings (TBCs) have been investigated and the thermal durability related to the microstructural evolution has been evaluated through cyclic thermal exposure tests. TBC systems with thicknesses of 2000 and 200μm in the top and bond coats, respectively, were prepared with the air–plasma spray system using a 9MB gun with ZrO2–8wt.% Y2O3 (METCO 204 C-NS) for the top coat and Ni-based metallic powder (AMDRY 962) for the bond coat. The post heating was performed at a temperature of 1000°C for 3h with a heating rate of 5°C/min in flowing argon (Ar) gas at 200ml/min. The thermal exposure tests were performed with a dwell time of 60min for 874cycles using a specially designed apparatus—one side of the sample was exposed to a high temperature of 1100°C and the other side was air cooled to 950°C. The post heat treatment is an efficient process in improving the thermal durability of thick TBCs, and the TBC with porous microstructure obtained by controlling coating parameters shows a better thermal durability than those with intermediate or dense microstructures. Results indicate that post heat treatment and microstructural control are important in proposing efficient processes to improve the lifetime performance of thick TBCs in high-temperature environments.

On selective laser melting of ultra high carbon steel: Effect of scan speed and post heat treatment

AbstractSelective laser melting is a laser‐based additive manufacturing process applying layer manufacturing technology and is used to produce dense parts from metallic powders. The application of selective laser melting on carbon steels is still limited due to difficulties arising from carbon content. This experimental investigation aims at gaining an understanding of the application of the process on ultra high carbon steel, which is a special alloy with remarkable structural properties suitable for different industrial applications. The feedstock ultra high carbon steel (2.1% C) powder, 20 μm to 106 μm was prepared by water atomizing technique. This powder was used for the selective laser melting to build specimens 10×10×40 mm in dimensions. To decrease the thermal stresses during layer by layer building, laser scanning was done through 5×5 mm random island patterns while layer thickness was 30 μm. Laser beam diameter, maximum power output, layer thickness and scan speed range were 0.2 mm, 100 W, 30 μm and 50–200 mm/s respectively. The process was done inside high purity nitrogen environment, with less than 0.5% oxygen content. The results illustrate the influence of scan speed from 50 to 200 mm/s on product geometry and dimensions, surface roughness, internal porosity and cracks, microstructure and surface hardness. The effect of post heat treatment by heating and holding for one hour (annealing) at different temperatures of 700°C, 750°C, 950°C is studied. The results indicate that selective laser melting is able to produce near to 95% density of ultra high carbon steel parts with acceptable geometry and surface quality. Porosity cracks, and microstructure formed during the process could be controlled through proper selection of process parameters and post heat treatment. Industrial ultra high carbon steel products can be rapidly fabricated by selective laser melting.

Effect of iron particle addition on the pseudocapacitive performance of sol–gel derived manganese oxides film

Manganese oxide electrodes with promising behavior were prepared successfully by sol–gel process. Manganese oxide films were also modified with the addition of submicron-crystalline iron powders. Effects of post heat treatment and iron submicron-powder addition on the material characteristics and electrochemical capacitance of the manganese oxide electrodes were investigated. The experimental results showed that manganese oxide films composed from metal-organic precursors at 250 °C heat treatment, while formation of MnO2, Mn2O3, Mn3O4, Fe2O3, and Fe3O4 phases were observed after heat treatment at a temperature higher than 300 °C. The specific capacitances were 48.9, 140.1, 212.7, and 81.1 F g−1 for manganese oxide films heat treated at 250, 300, 350, and 400 °C, respectively. The specific capacitances were 75.7, 227.3, 247.9, and 152.9 F g−1 for manganese/iron oxide films (Mn:Fe = 100:1) heat treated at 250, 300, 350, and 400 °C, respectively. The manganese/iron oxide films (Mn:Fe = 100:1) treated at 350 °C exhibited the highest specific capacitance 247.9 F g−1 of the electrodes investigated in the present study. After 1000 cyclic voltammetry tests, the specific capacitance decreased by only 10 percent. The surface morphology of this film exhibited powders with linked nano-sized particles. The number of special particles reached a maximum after heat treatment at 350 °C. The experimental results showed that post heat treatment and iron submicron-particle addition may change the surface morphology and structure, increase the specific capacitance, and improve the electrochemical performances of the manganese oxide electrodes.

Growth, characterization and studying of sol–gel derived CdS nanoscrystalline thin films incorporated in polyethyleneglycol: Effects of post-heat treatment

In this study, the CdS nanocrystalline thin films elaborated by sol–gel dip-coating process with a less reported precursor based on polyethyleneglycol matrix. After heat treatments in air at different annealing temperatures, the prepared thin films were investigated by studying their structural, morphological, compositional, d.c. electrical, optical (linear and nonlinear) and photoluminescence properties. X-ray diffraction (XRD) results suggest that the samples are polycrystalline in nature with a mixed (cubic+hexagonal) crystal structure and the average grain size is in the range of 12.84–20.55nm. The phase transformation was occurred at 350°C to hexagonal structure. The surface morphology of the films was examined by scanning electron microscopy (SEM). The results revealed that the films consist of nanocrystalline grains with uniform coverage of the substrate surface. To examine the chemical composition of the films, the X-ray photoelectron spectra (XPS) of the composite films were measured. As the annealing temperature increased from 250 to 450°C the mobility enhanced from 42.99 to 296.20cm2V−1s−1, respectively. It was found that the transmittance and the band gap decreased as the annealing temperature increased. The optical constants of the films were studied and the dispersion of the refractive index was discussed in terms of the Wemple–Didomenico single oscillator model. The real and imaginary parts of the dielectric constant of the films were determined too. It was also observed that the volume energy loss (VELF) increases more than the surface energy loss (SELF) at their particular peaks. The third-order nonlinear polarizability parameter is higher for CdS thin films with smaller crystallite size. Multiple Cd and S defects were observed by employing photoluminescence (PL) method. The intensities of emission peaks for the prepared thin films varied with annealing temperature and the behaviors of different band peaks were discussed with giving reasons.