Effect Of Post Heat Treatment Research Articles

Effect of Post-Heat Treatment on Superconducting Properties of Nb3Al Wires Prepared With RHQ Process at Different Conditions

Effect of Post-Heat Treatment on Superconducting Properties of Nb₃Al Wires Prepared With RHQ Process at Different Conditions

Effect of post heat treatment on tensile strength of dissimilar aluminum alloy joints manufactured through powder bed fusion process

Effect of post heat treatment on tensile strength of dissimilar aluminum alloy joints manufactured through powder bed fusion process

Fatigue properties of removable partial denture clasps fabricated by selective laser melting followed by heat treatment

The aim of the study was to investigate the effect of post-heat treatment on the microstructures and fatigue strengths of Co–Cr–Mo (CCM) clasps prepared by selective laser melting (SLM). Clasp specimens and rod-shaped specimens were fabricated by SLM using CCM powders with different angulations (0°, 45°, and 90°). Two heat treatment conditions were used: 1 and 6 h at 1150 °C in an argon atmosphere followed by cooling in a furnace. Subsequently, the fatigue strength and microstructure were investigated. The results revealed that for the control group, the mean fatigue life was different when building angulations were changed as manifested by the control-90 specimen, which exhibited the highest fatigue life, followed by control-45 and then control-0. One-hour heat treated samples showed higher fatigue strength in all axes than the 0°- and 45°-axes control samples and lower fatigue strength than the 90°-axes control samples. The survival rate after heat treatment for 1 h exhibited no significant difference in all the axes. In terms of microstructure, after heat treatment, the samples showed homogeneous equiaxed grain and randomized texture in all angulations. Therefore, using a post-heat treatment can reduce the anisotropy effect on the microstructure and fatigue strength due to homogenized microstructure.

Solution Processed Bi-Based Sensitized Solar Cell: Effects of Post Heat Treatment.

Nanosize semiconductors have been used as active sensitizers for the application of quantum dot-sensitized solar cells (QDSSC). "Green" sensitizers are introduced as an alternative for the toxic Cd and Pb based compounds. In this work, Bi₂S₃ quantum dots (QDs) were fabricated and used as sensitizers in QDSSC. QDs were grown on TiO₂ electrode via solution dipping process. Although the performance of "green" QDSSC is not as high as that of CdS or CdSe based QDSSCs, its performance can be enhanced with post heat treatment. The effect is dependent on the heat treatment temperature profile where gradual increase of sintering temperature is preferred. The effects of post heat treatment on Bi₂S₃ sensitized TiO₂ electrodes are investigated and discussed.

Synthesis, characterization and tribological behavior of electrodeposited nanostructured Co–23 wt.% Sn coatings

Nowadays thin layers are extensively applied in a variety of technological and industrial applications, which can range from microelectronics up to transportation field. In these diverse applications, thin layers should operate under different tribological contact conditions. In this work, nanostructured Co– 23 wt.% Sn alloy electrocoatings were developed as replacements to hard chrome. However, in order to explore the potential applicability of this newly developed material, a study of the structure, mechanical and tribological properties should be performed. In addition, their tribological behavior should be studied under a wide range of contact conditions to simulate meso-load (e.g. met in MEMs and watch industry) and macro-load (e.g. met in automotive industry) contacts, as friction and wear are load dependent. For this reason, reciprocating sliding tests against an inert alumina countermaterial were performed in the mN (Hertzian contact pressure 250-560 MPa) and N (Hertzian contact pressure 470-650 MPa) load range. The aim is to illustrate that despite having similar contact pressures, different tribological phenomena can occur in these scales. Furthermore, the effect of post heat treatment was also investigated, since electrodeposition is a non-equilibrium process and structural changes might occur during heating-up.

Effect of post heat-treatment on the microstructure and mechanical properties of Hastelloy-X structures manufactured by laser based Directed Energy Deposition

This paper reports a systematic investigation of Hastelloy-X (Hast-X) structures built by Laser Directed Energy Deposition in as-built and post heat-treated conditions. The optical microscopy shows microstructures with fine dendrites in as-built condition due to higher cooling rate during deposition, while recrystallized equiaxed grains are observed after post heat-treatment (at 1177 °C) due to recrystallization. X-ray diffraction studies reveal nickel γ-matrix with variation in crystallite size and a peak shift after post heat-treatment, primarily due to change in surface residual stress. Surface topography reveals the reduction in average roughness with post heat-treatment. Further, the maximum compressive residual stress of 350 MPa and maximum tensile residual stress of 252 MPa are observed at the surfaces of post heat-treated and as-built samples, respectively. The average micro-hardness changed from 239 HV1.96N to 208 HV1.96N after post heat-treatment. Single Cycle Ball Indentation studies indicated increase in energy storage capacity by a factor of 1.55 after post heat-treatment. Automated Ball Indentation studies quantify yield strength and ultimate strength as 478 MPa and 765 MPa in as-built samples, while 393 MPa and 630 MPa in post heat-treated samples, respectively. Further, crack propagation studies indicate an improvement in the fatigue life after post heat-treatment, while the specific wear rate increased by a factor of 1.72 with increased delamination in heat-treated samples. Thus, post heat-treatment of Hast-X samples changes the material properties significantly.

Effect of post-heat treatment on residual stress and tensile strength of hybrid additive and subtractive manufacturing

This paper presents a comprehensive study of the tensile performance, heat treatment, fracture, decrease of residual stress, second-phase particle and microstructures of a 316L stainless steel fabricated by directed laser deposition (DLD) and thermal milling (starting milling temperature at 250 ± 50 °C), a typical hybrid additive and subtractive manufacturing process. Experiments of different post-heat treatment temperatures and tensile tests at room temperature were performed. The residual stress was eliminated with heat treatment at 400 °C for 2 h, and the average residual stress decreased 53.7% while the yield strength and ultimate strength decreased slightly. The fracture surfaces of different heat treatment temperatures were observed. The typical ductile fracture microstructures of dimples were seen in almost all specimens whenever the heat treatment temperature was low or high. The evolution of dimples from formation to destruction by heat treatment was analyzed. The different morphology and composition of the second-phase particles of different heat treatment temperatures were compared. The yield strength of 427.5 MPa, the ultimate strength of 599.27 MPa, and the elongation of 36.48% showed the new hybrid manufacturing technology could be used for further fabrication of components.

Manufacturing of high-strength laser welded joints of an industrial aluminum alloy of system Al-Cu-Li by means of post heat treatment

This work aims to study the effects of post heat treatment by quenching and artificial aging on the mechanical characteristics (strength, microhardness) and microstructure of laser welded joints of aluminum alloy V-1461 of the system Al-Cu-Li. Heat treatment regimes were identified in which the tensile strength, yield strength, and relative elongation of the welded specimens are respectively 92%; 91%, and 88% of the base alloy characteristics.

Effect of post-heat treatment on the microstructure of micro-plasma sprayed hydroxyapatite coatings

Hydroxyapatite (HA) is widely used as surface coatings on biomedical metal implants because of its excellent biocompatibility and osteoconductivity. In this study, HA coatings were deposited onto Ti-6Al-4V substrates by micro-plasma spraying and then heat treated at 650 °C in a muffle furnace for 3 h and 6 h. XRD results showed that, the HA peaks were sharper than those of corresponding as-sprayed coatings and the amorphous diffuse background was reduced after heat treatment. The transformation from impurity phases such as tetra-calcium phosphate (TTCP) and tri-calcium phosphate (TCP) and amorphous calcium phosphate (ACP) to crystalline HA occurred during the heat treatment. Moreover, the texture intensity was not increased during the re-crystallization of ACP and the transformation of impurity phases into HA. The SEM results showed that nanograins were formed on the coating surface. In addition, with the increase of the holding time, the nanograins become coarse.

Effect of post-heat treatment on the creep behaviour at 550°C of NiCr+Cr3C2 coating produced by HVOF on the SUS 304 substrate

Austenitic Stainless Steel Grade 304 which is used for power plants boiler pipes often occurs creep phenomenon that caused a decrease in performance due to work at elevated temperatures. Surface coating of SUS 304 with Metal Matrix Composites Coating feedstock material 60%NiCr + 40%Cr3C2 is deposited using high-velocity oxygen fuel (HVOF) technique. The post-annealing process at 600°C at an argon atmosphere, holding time for 3 hours, and cooling in the furnace. Creep resistance test was carried out at a temperature of 550°C with a load of 54 kg for 10080 hours on three specimens, i.e non-spray, as-spray, as-annealed, then followed by microstructure hardness testing and porosity observation. As-annealed specimens were assessed that the lowest creep resistance value, increased hardness in the coating and substrate and decreased the percentage of porosity in the coating.

Effect of Post-heat Treatment on the Corrosion Behavior of AlSi10Mg Alloy Produced by Additive Manufacturing

Additive manufacturing processes are becoming attractive technologies for producing complex components in relatively a short time and at reasonable cost. The present study aims to evaluate the effect of post-heat treatment on the corrosion performance of AlSi10Mg alloy produced by selective laser melting (SLM). Heat treatment up to 400°C for 2 h was tested. Microstructure evaluation was carried out using optical and scanning electron microscopy, along with x-ray diffraction assessment and photoelectron spectroscopy analysis. Corrosion performance was studied by salt spray testing, potentiodynamic polarization and electrochemical impedance spectroscopy for general corrosion assessment, while slow strain rate testing and low cycle corrosion fatigue were employed for stress corrosion examination. The obtained results indicated that relatively improved corrosion performance was achieved by heat treatment at 200–300°C. This was mainly attributed to the preservation of the fine Si net embedded in the α-Al matrix that was obtained during the SLM process and the adequate residual stress relief conditions.

Adverse effects of post-heat treatment on the interfacial bonding strength of direct laser deposition Inconel 625/1045 composites

Interfacial bonding strength is critical to the service life of components in the remanufacturing field. To identify the interfacial mechanical properties, a nickel-based Inconel 625 alloy powder was deposited on the AISI 1045 steel substrate by direct laser deposition. The effects of post-heat treatment on the phase transformation, composition segregation and residual stress releasing near the interface were investigated. A series of microstructural characterizations, such as SEM, FE-SEM, EDS and XRD, were used. By uniaxial tensile experiments, the interfacial bonding strength with/without post-heat treatment were compared, we found that the interfacial bonding strength of original specimen (556.8 MPa) was stronger than that of post-heat treatment (452.3 MPa). This was attributed to the fact that the thermal expansion coefficient of Inconel 625 powder (αd = 14.7) was less than that of the AISI 1045 substrate (αs = 15.6), resulting in the compressive residual stress at the edge of interface. After post-heat treatment, the release of beneficial compressive residual stress and the change of phase composition near the interface were the reasons for the decrease of interfacial bonding strength. These results indicated that post-heat treatment is not suitable for all heterogeneous bonding materials. This kind of material matching (αd < αs) is more advantageous to remanufacturing field.

Strategy of incorporating Ni-based braze alloy in cold sprayed Inconel 718 coating

Ni-based superalloy (Inconel 718) and Ni-based braze alloy (MAR-M 002) composite coatings were deposited on Inconel 718 substrates via a high-pressure cold spray process. The effects of post heat treatment on microstructural evolution and chemical diffusion of the composite coatings were systematically investigated. The microstructures of the powders and composite coatings were investigated using scanning electron microscopy, electron backscatter diffraction, energy-dispersive X-ray spectroscopy and nanoindentation. After cold spray deposition, it was found that MAR-M 002 particles were uniformly distributed within the as-sprayed composite coatings. During the heat treatment process, it was noted that the diffusion of chemical species occurred across the Inconel 718 and MAR-M 002 particulate interfaces with the width of the diffusion zone being around 10 μm. The enhanced chemical diffusion between Inconel 718 and MAR-M 002 particles could effectively heal out the splat boundaries and reduce coating porosity, which was proved with the microstructure analysis. The effect of chemical diffusion on interparticle bonding strength was investigated through tensile testing. The heat-treated Inconel 718/MAR-M 002 composite coating had a tensile strength of about 810 MPa that was about 17% higher compared to the heat-treated pure Inconel 718 coating. From the SEM observations, the fractured surface of the heat-treated IN718/MAR-M 002 composite specimen was characterized by the presence of more dimples, which indicated a higher fraction of metallurgically bonded interparticle boundaries. These results demonstrated that the proposed methodology for the formation of Inconel 718/MAR-M 002 composite deposits was beneficial for improving the interparticle bonding strength in the deposits.

Additive Manufacturing of High-Entropy Alloys: A Review.

Owing to the reduced defects, low cost, and high efficiency, the additive manufacturing (AM) technique has attracted increasingly attention and has been applied in high-entropy alloys (HEAs) in recent years. It was found that AM-processed HEAs possess an optimized microstructure and improved mechanical properties. However, no report has been proposed to review the application of the AM method in preparing bulk HEAs. Hence, it is necessary to introduce AM-processed HEAs in terms of applications, microstructures, mechanical properties, and challenges to provide readers with fundamental understanding. Specifically, we reviewed (1) the application of AM methods in the fabrication of HEAs and (2) the post-heat treatment effect on the microstructural evolution and mechanical properties. Compared with the casting counterparts, AM-HEAs were found to have a superior yield strength and ductility as a consequence of the fine microstructure formed during the rapid solidification in the fabrication process. The post-treatment, such as high isostatic pressing (HIP), can further enhance their properties by removing the existing fabrication defects and residual stress in the AM-HEAs. Furthermore, the mechanical properties can be tuned by either reducing the pre-heating temperature to hinder the phase partitioning or modifying the composition of the HEA to stabilize the solid-solution phase or ductile intermetallic phase in AM materials. Moreover, the processing parameters, fabrication orientation, and scanning method can be optimized to further improve the mechanical performance of the as-built-HEAs.

Effect of post heat treatment on the microstructure and microhardness of diffusion coupled gray cast iron and low carbon steel

Experimental studies carried out on the joining of grey lamellar graphite cast iron to low carbon steel by diffusion welding techniques had successfully produced a few diffusion couples, despite facing some earlier failures. Although faced with some success, analysis on the diffusion couples showed voids and incomplete bond/joint at the interface of the joints while the tensile strength value was found to be low. In furtherance, the diffusion couples were then subjected to a post-weld heat treatment (PWHT) that allowed for further diffusion process to take place to remove the voids and complete the bond/weld. The results revealed microvoids and interface lines at the interfaces of the specimens treated at temperatures of 800°C, and becoming less visible at 900°C. At an elevated temperature of 1000°C, on longer treatment times, apparently these microvoids and interface lines had disappeared, and the bond/weld at the interfaces of the diffusional welded couples seemed to be more complete. Thus, heat treatment time and temperature were found to have a strong influence on the structure, thickness and hardness of the diffusion layer produced.

Effect of Post Weld Heat Treatment on the Microstructure and Mechanical Properties of a Submerged-Arc-Welded 304 Stainless Steel

The present study is to investigate the effect of post heat treatment on the microstructures and mechanical properties of a submerged-arc-welded 304 stainless steel. The base material consisted of austenite and long strips of delta-ferrite surrounded by Cr-carbide, and the welds consisted of delta ferrite and austenite matrix. For the heat treatment at 850 °C or lower, Cr-carbides were precipitated in the weld metal resulting in the reduction of elongation. The strength, however, was slightly reduced despite the presence of Cr-carbides and this could possibly be explained by the relaxation of internal stress and the weakening of particle hardening. In the heat treatment at 1050 °C, the dissolution of Cr-carbide and disappearance of delta ferrite resulted in the lower yield strength and higher elongation partially assisted from deformation-induced martensitic transformation. Consequently, superior property in terms of fracture toughness was achieved by the heat treatment at 1050 °C, suggesting that the mechanical properties of the as-weld metal can be enhanced by controlling the post weld heat treatment.

Mechanical properties of tailor welded Al/Steel blanks made by friction stir welding and the effect of post heat treatment

Aluminum (Al) alloy, A6061-T6, plate and stainless steel, SUS304, plate with different thicknesses were butt welded by a friction stir welding (FSW) process to fabricate tailored blanks. The Al plate was thicker than the steel plate. The FSW tool was offset to the Al side and the probe was inserted only into the Al plate. The shoulder of the tool was also plunged only into the Al plate because of the different thicknesses of the plates. The microstructural observation and X-ray CT revealed that small steel fragments were dispersed in Al-side stir zone (SZ) due to the scratching of steel side surface by the probe. The hardness of SZ in Al side was lower than the base metal due to the dissolution of hardening precipitates during welding, where the lowest hardness located near the thermo-mechanically affected zone (TMAZ) in Al side. The tensile failure occurred at TMAZ because of the bonding strength between Al and steel was higher than TMAZ. However, the tensile strength of the dissimilar weld was approximately 38% lower than that of the aluminum alloy base metal due to the softening at TMAZ. Post heat treatment increased the hardness at TMAZ, whilst the tensile strength was still about 33% lower than the base metal.

Effect of post-heat treatment on the mechanical properties of surface-tolerant epoxy coated on API 5L X65 carbon steel pipe: pipeline industry application

In the present work, a post-heat treatment was used to improve the mechanical properties of surface-tolerant epoxy coated API 5L grade X65 carbon steel pipe. For each carbon steel pipe coated with surface-tolerant epoxy, the mechanical properties including hardness and adhesive strength are measured by Shore D Durometer testing (impact resistance) and Hydraulic Adhesion tester (pull-off resistance). The mixing times, also known as the pot life timing, of the epoxy used in this experiment were 5, 15 and 30 minutes, and after mixing, the surface-tolerant epoxy’s viscosity was measured by Viscometer. The post-heat treatment temperatures of the fully cured surface-tolerant epoxy coated on the carbon steel pipe used in this study were room temperature, 50°C, 100°C, and 150°C over 24 hours. It was found that post-heat treatment results in the improvement of adhesive strength more than hardness. The maximum percentage of hardness and adhesive strength improvement after post-heat treatment was 6.47% and 37.04%, respectively.

Microstructure and mechanical properties of Inconel 718 produced by selective laser melting: Sample orientation dependence and effects of post heat treatments

Inconel 718 produced by selective laser melting (SLM) has been characterized with focus on the microstructure, the dependence of sample orientation on the mechanical properties and the effects of post heat treatments. The as-manufactured IN718 has a very fine cellular-dendritic structure with fine Laves phases precipitating in the interdendritic region, and electron backscatter diffraction (EBSD) analysis shows that both the vertically and horizontally built samples have relatively weak texture. The vertically built samples show lower tensile strength but higher ductility than the horizontally built samples, and the mechanism is shown to be partly due to the crystallographic feature but more importantly due to the different amount of residual stress and dislocations accumulated in these two kinds of samples. Applying heat treatments can significantly increase the strength while decrease the ductility correspondingly, and difference in yield strength between the vertically and horizontally built samples decreases with increasing the heat treatment temperatures, mainly due to the removal of residual stress and dislocations.

Evaluation and comparison the effect of heat treatment on mechanical properties of NiCrBSi thermally sprayed coatings

PurposeThis study aims to investigate the effect of post heat treatment on mechanical properties of NiCrBSi coatings, which were applied on 316L stainless steel using high-velocity oxygen-fuel (HVOF) and flame spray techniques.Design/methodology/approachThe properties of coatings were investigated by metallographic characterizations as well as wear, micro-hardness and adhesion tests.FindingsThe micro-hardness results showed that the coatings considerably increased the sub-layer hardness. In addition, regarding the wear test results, it can be seen that heat treatment increased wear resistance of the coatings. These thermal sprayed coatings are usually re-melted by post heat treatment, leading to improvement in tribological properties. The results obtained revealed that re-melting procedure improved the metallurgical bonding in the substrate\\coating interface.Originality/valueMicrostructure defects resulting from thermal spraying such as pores and unmelted particles can be eliminated by post heat treatment. This process can considerably improve the corrosion and wear resistances of the thermal sprayed coatings.