Effect Of Heat Treatment Research Articles

Effect of stress-relief heat treatment on the stress-rupture properties of a nickel-based superalloy manufactured by laser powder bed fusion

Residual stress is a ubiquitous phenomenon in laser powder bed fusion (LPBF) metal parts due to high temperature gradients and uneven heating during building processes. Subsequent stress-relief (SR) heat treatment is usually conducted to reduce the geometrical distortion and microscopic cracks induced by residual stress after the LPBF process. Using electron microscopy, X-ray diffraction, and stress-rupture tests, the experimental results revealed that the stress-rupture life of a nickel-based superalloy, IN625 alloy, subjected to SR treatment at 870°C and 980°C is inferior to that of the as-built (AB) alloy. The fundamental cause for this phenomenon is that more δ phase precipitates in the grains of the AB alloy during the stress-rupture test at 750°C/230 MPa, resulting in an increased dispersion hardening effect and a decreased ductility. Furthermore, the Laves and δ phases along grain boundaries in the SR treated alloys are more likely to coarsen, which is the second reason for the decreased stress-rupture life of the SR treated alloys.

Effects of carbon content and heat treatment on wear-resistance and impact properties of novel cast steels with bainitic and martensitic structure

Abstract The traditional material for caterpillar boards is mainly Hadfield steel. The wear resistance of the Hadfield steel cannot be fully exerted due to insufficient work hardening during the operation of the caterpillar board. The effects of carbon content and heat treatment on the wear-resistant and impact properties of a novel caterpillar board cast steels with bainitic and martensitic structures have been investigated. The microstructural observation of worn surface topography was performed by scanning an electronic microscope, and the impact toughness was carried out by an impact tester, in a bid to improve the wear-resistant properties and its impact toughness. The results demonstrate that the hardness and wear-resistant properties of cast steels increase with the increase of carbon content, whereas the impact properties reduce because the brittle phases, such as the carbide precipitation and the martensite, are more. The heat treatment temperature of steels can change the relative ratio of bainitic and martensitic structures, thus affecting the wear-resistant properties of the steels. By controlling the carbon content and heat treatment processing of the steels, the optimal combination of toughness and wear-resistant properties can be achieved. The wear mechanism of dual-phase cast steel was analyzed through wear resistance tests, and it also shows that dual-phase cast steel with bainitic and martensitic structures had better wear-resistance properties compared to the Hadfield steel at low-impact wear conditions.

Effect of heat treatment on performance of high-temperature thermistor LaCrO3

Effect of heat treatment on performance of high-temperature thermistor LaCrO3

Effect of post weld heat treatment on microstructural and mechanical properties of martensitic heat-resistant steel weldments

Martensitic heat-resistant steel (MHRS) serves as an important structural material for manufacturing ultra-supercritical unit due to its excellent fatigue resistance and corrosion resistance. Post weld heat treatment (PWHT) is a common method for regulating the microstructure and properties of MHRS welded parts. In this work, we investigated the influence of different PWHT methods on the microstructure, mechanical properties, and room temperature creep properties of Co3W2 welded joints. The results showed that post-weld direct tempering (PWDT) or post-weld re-automatizing and tempering (PWNT) treatment significantly reduces the differences in microstructure and local mechanical properties of as-welded joints. Compared to the as-welded specimens, the PWDT and PWNT welds show lower strength and hardness, but better impact resistance. The PWNT treated welds show more homogeneous microstructure and local mechanical performance, and better tensile property and impact resistance than PWDT welds. Furthermore, the fine grain heat affected zone in PWNT welds shows the smallest strain rate sensitivity value, which implies the PWNT method may alleviate type IV brittle fracture in martensitic heat-resistant steel weldments.

Effect of Deformation and Subsequent Heat Treatment on Sigma-Phase Precipitation and Mechanical Property of CoCrFeMnNi High Entropy Alloy

Effect of Deformation and Subsequent Heat Treatment on Sigma-Phase Precipitation and Mechanical Property of CoCrFeMnNi High Entropy Alloy

In vitro simulated digestion of different heat treatments sweet potato polysaccharides and effects on human intestinal flora

The aim of this study was to investigate the changes of untreated and steamed (100 °C, 20 min), fried (150 °C, 10 min), and baked (200 °C, 30 min) sweet potato polysaccharides during in vitro digestion and their effects on the intestinal flora. The results showed that the reducing sugar content of all four sweet potato polysaccharides increased significantly during digestion. During in vitro fecal fermentation, the content of reducing sugars and total carbohydrates decreased significantly. It indicated that all four polysaccharides showed degradation of polysaccharides during fermentation. Compared to the blank group, the total SCFAs content of the four polysaccharide sample groups was significantly increased. It was worth noting that sweet potato polysaccharides increased the percentage of Bacteroidetes and decreased the percentage of Proteobacteria in the intestinal flora. The findings provide evidence that sweet potato polysaccharides regulate intestinal flora and maintain intestinal health through interactions with intestinal flora.

Effect of heat treatment on the corrosion resistance of 316L stainless steel manufactured by laser powder bed fusion

Understanding the influence mechanism of microstructures and inclusions during heat treatment on the corrosion resistance of L-PBF 316L stainless steel (SS) is crucial for steel quality control and subsequent industrial application. In this study, the evolution of microstructure, inclusions and passive film in the L-PBF 316L SS during heat treatment at the temperature of 1000 °C and 1200 °C for 2 h, including crystal characteristics, dislocation density, passivation film composition and so on, were characterized by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of L-PBF 316L SS samples was evaluated by Tafel test and electrochemical impedance spectroscopy test. The corrosion mechanisms of L-PBF 316L SS before and after heat treatment were clarified to elucidate the intrinsic effect of microstructure and inclusions on the corrosion resistance of the steel. Results showed that the heat treatment conducted at 1200 °C effectively reduced the number of grain boundaries and induced a substantial number of Σ3 twin grain boundaries in the L-PBF 316L SS, thereby efficiently impeding the precipitation of detrimental phases and reducing corrosion susceptibility at the grain boundaries. Meanwhile, the recrystallization-induced rearrangement of dislocations and the homogenization of grains effectively facilitated the growth of passivation film, thereby increasing the corrosion resistance of HT1200 sample. Additionally, the increase of MoO3 content compensated for the detrimental impact on the stability of the passivation film resulting from the reduction in chromium oxide content. Transformation from the MnO–SiO2–Cr2O3 inclusions in the as-built sample to the SiO2 inclusions in the HT1200 sample would also retard the penetration of corrosive ions into the steel matrix.

Effect of Heat Treatments on the Mechanical and Microstructure Properties of Welded API X70 Steel

Effect of Heat Treatments on the Mechanical and Microstructure Properties of Welded API X70 Steel

Effect of heat treatment on the microstructure, mechanical properties and fracture behaviors of ultra-high-strength SiC/Al–Zn–Mg–Cu composites

Effect of heat treatment on the microstructure, mechanical properties and fracture behaviors of ultra-high-strength SiC/Al–Zn–Mg–Cu composites

Effect of Heat Treatment on the Color and Hardness of Some Imported Wood Species for Decking

Effect of Heat Treatment on the Color and Hardness of Some Imported Wood Species for Decking

Effect of heat treatment on the microstructure and mechanical properties of 18Ni 300 maraging steel manufactured by wire + arc additive manufacturing

ABSTRACT A thin-walled structure was manufactured by wire + arc additive manufacturing using 18Ni 300 maraging steel, and the heat treatment process had been investigated. The microstructure of as-deposited sample was martensite, ferrite and nano-precipitated phases. Differently, more nano-precipitated phases and reverted austenite existed in the direct aging (AT) sample. However, only lath martensite and nano-precipitated phases existed in the solution + aging (SAT) sample. The as-deposited and AT samples performed a high strength with well plastic. The primary strengthening mechanism for this great improvement of tensile strength arose by the formation of nano-precipitated phases, which was known as the Orowan strengthening mechanism. The well plastic of as-deposited and AT samples was attributed to dual phase net basket sub-structures, which were beneficial to improve the length of crack propagation and the ability of cooperative deformation. And the reverted austenite was also main factor for the well plastic of the AT samples.

Effect of heat treatment on microstructure and mechanical properties of lightweight high-entropy alloy

High-performance lightweight materials are in demand for a wide range of critical applications in the automotive, aviation, and aerospace industries. However, it remains difficult to enhance the strength of these alloys without significantly reducing their tensile ductility. Here, using different heat treatment routes, we overcome this inherent strength and ductility trade-off dilemma by introducing low lattice misfit precipitates in a lightweight high-entropy alloy (LHEA). In particular, the A700 alloy exhibits a high yield strength of 609 MPa and a tensile ductility of ∼24 % at room temperature, benefitting from the highly dispersed, low lattice misfit L12 and nano-lamellar body-centered cubic (BCC) phases.

Effect of heat treatment on electromagnetic shielding performance of electroless copper-nickel on wood

The wood-based composites have received extensive attention in the field of electromagnetic interference (EMI) due to inherent layered porous structure. In this study, the deposition Ni and Cu-Ni on wood surface and heat treatment temperature were used as variables. The variation law of electromagnetic shielding (EMS) performance of composite materials is analyzed. The results showed that Ni particles were fully filled in the layered porous structure of the wood, and the metal coatings evenly covered the entire wood surface. The Ni content of the wood based composite materials via 260 °C heat treatment was up to 98.04 %. The pore structure was more regular with the increase of the number of deposition Ni. The ideal roughness was 11.33 μm and the conductivity reached a maximum of 46.8 S/cm at 200 °C. The EMS effectiveness of one deposition Ni composite materials showed an increasing trend when the heat treatment was 200 ℃, 220 ℃, 240 ℃, 260 ℃ and 280 ℃, respectively. When the heat treatment temperature is 260 °C, the EMS effectiveness of the wood-based composite material can reach 88.76 dB, and the hydrophobicity can reach 99.55 °. When the temperature is 300 °C, the electromagnetic shielding effectiveness can reach 91 dB, and the hydrophobicity can reach 117 °. The anisotropic internal porous structure of wood matrix and the multi-interface polarization between wood and Cu-Ni are the main reasons for the high EMS performance.

The Effect of Aging Heat Treatments on Room and High-Temperature Wear Performance of the Inconel 718™ Manufactured by Laser Powder Bed Fusion

The Effect of Aging Heat Treatments on Room and High-Temperature Wear Performance of the Inconel 718™ Manufactured by Laser Powder Bed Fusion

Effect of heat treatment on the anisotropic machinability of additive manufactured titanium alloys in micro-milling

For titanium alloy parts prepared by selective laser melting (SLM), post-treatment operation is usually utilized to meet the needed surface accuracy and dimensional tolerances. However, the heat treatment process and anisotropy of different surfaces of SLMed titanium alloy can directly affect its machinability. In this study, the anisotropic machinability of SLMed TC4 before and after heat treatment was comprehensively compared by the milling force, surface quality, top-burr and work hardening. The results indicate that the milling force and work hardening degree of top surface of SLMed TC4 material are larger than those of side surface, and top surface the presents the better surface quality and smaller top-burr. It exhibits obvious anisotropic machinability in micro-milling. After heat treatment, the anisotropic machinability between different surfaces of SLMed TC4 materials were significantly reduced. The average surface roughness difference rate of top and side surfaces decreased from 10.08% to 2.79%, and the total average top-burr size difference rate decreased from 19.53% to 9.99%. The difference rate of milling force and work hardening degree of the top and side surfaces both showed a decreasing trend. This work demonstrates that the anisotropic machinability of SLMed TC4 material in micro-milling can be effectively mitigated by the heat treatment process.

Effects of post-weld heat treatment on microstructure, tensile properties and linear expansion behavior of laser welded Invar alloy

To improve the ductility and toughness of 4J36 Invar alloy welded joints, this study investigates the microstructure evolution of laser welded 4J36 Invar alloy joints under different annealing temperatures, and evaluates the changes in the thermal expansion coefficient (TEC) of the joints after heat treatment. The results indicated that the 4J36 Invar alloy joints maintain a single austenitic phase after annealing at different temperatures, but the grain morphology and size change significantly. Compared to the welded joint without heat treatment, the ductility of the heat-treated one increased by 94 %, which reached 39.2 %. The TEC of the Invar joints increases with the increase of annealing temperature. The optimal process parameters are an annealing temperature of 650 °C and a holding time of 1.5 h. Under these conditions, the welded joint exhibits a strength close to that of the base material, with improved ductility and relatively low TEC.

Effect of Solution and Aging Heat Treatment on the Microstructure and Mechanical Properties of Inconel 625 Deposited Metal

Inconel 625 deposited metal was prepared by gas metal arc welding. The solid solution treatment temperature was set at 1140 °C for 4 h using the DSC test method, followed by secondary aging at 750 °C/4 h and 650 °C/24 h. The specimens in the prepared state and after heat treatment were subjected to high temperature tensile at 600 °C, respectively. The fracture morphology, thermal deformation behavior, and strengthening mechanism of the samples in different states were analyzed. The results showed that the stress–strain curves of the deposited metals exhibited obvious work-hardening behavior at 600 °C. The solid solution and aging heat-treated samples have higher tensile and yield strength, but the plasticity is obviously lower than that of the deposited metal. It was also found that the γ″ phase and M23C6 carbides, as well as the continuous stacking faults in the alloy, were the main reasons for the increase in tensile strength of the solution and aging heat-treated sample.

The Effect of Heat Treatment on the Hardness of Medium Carbon Steel

The Effect of Heat Treatment on the Hardness of Medium Carbon Steel

Effect of Direct Aging Heat Treatment on Microstructure and Mechanical Properties of Laser Powder Bed Fused Maraging Steel 300-Grade Alloy

Abstract This paper investigates the effects of a 6-hour direct aging heat treatment at 490 °C on the mechanical, tribological, and microstructure characteristics of laser powder bed fused maraging 300 steels, which is produced at various laser energy densities. After direct aging heat treatment, the grain boundaries become irregular and vague due to the residual stress releasing, squeezing of precipitates into the grain boundaries, and phase transformations. The XRD analysis reveals the reverted austenite (γ′) phase forms during aging treatment due to the inevitable reversion of metastable martensite to the stable reverted γ′ phase. The heat-treated samples' microhardness rises with rising the laser energy density (LED) from 61.41 to 92.10 J/mm3 due to a decrease in the reversed austenite phase and a further rise in LED decreases the microhardness of heat-treated samples due to a rise in the reversed austenite phase after heat treatment. The heat-treated sample produced at LED of 92.10 J/mm3 shows maximum yield, ultimate tensile strengths, and minimum elongation percentage due to its high microhardness, and the fractography results show the failure mode as a mixed brittle and ductile fracture. The wear-rate of the heat-treated additively manufactured maraging 300 steel decreases as the LED increases from 61.41 to 92.1 J/mm3 and a further rise in LED from 92.10 J/mm3 to 166.66 J/mm3, the wear-rate increases. The wear-rate rises with a rise in sliding velocity from 1.5–3.5 m/s. The dominant wear mechanism was observed as abrasion with small grooves and saplings.

DEVELOPING HIGH-PERFORMANCE LOW-TEMPERATURE CO2 GAS SENSORS BASED ON NANOSTRUCTURED CO3O4 THIN FILMS: A SOL–GEL APPROACH AND THE ROLE OF ANNEALING

In this study, we synthesized Co3O4 thin films using a sol–gel spin coating method and investigated the effect of heat treatment on their carbon dioxide (CO2) gas sensing properties. To optimize their crystallinity and enhance their CO2 sensitivity, the thin films were annealed at temperatures ranging from 400∘C to 550∘C. We characterized the morphological, structural, electrical, and optical properties of the Co3O4 thin films to gain insights into their behavior in the low operating temperature range (OTR). Our X-ray diffraction (XRD) analysis revealed that all the thin films exhibited a cubic structure, with improved crystallinity observed at higher annealing temperatures. We observed a decrease in band edges in the optical transmittance spectra of the thin films as the annealing temperature increased, indicating a redshift in the absorption edge. Notably, the highest electrical conductivity was observed for the sample annealed at 550∘C, suggesting enhanced crystallinity and improved CO2 gas sensitivity. These findings provide valuable insights into the optimization of Co3O4 thin films for CO2 gas sensing applications.