Thermal Tempering Research Articles

Numerical modeling and statistical analysis of the effect of thermomechanical properties on residual stresses in feldspar‐based ceramic materials after thermal tempering

AbstractThis study focuses on the investigation of the impact of the thermomechanical properties of ceramic materials on residual stresses generated after the thermal tempering process. A sodium feldspar matrix was chosen for numerical simulations, with variations in its thermomechanical properties of up to ± 20%, to encompass a range of properties exhibited by other ceramic materials. The simulations demonstrated that the viscosity of the material had the most significant influence on residual stress generation, while the coefficient of thermal expansion, modulus of elasticity, and effective diffusivity also contributed to residual stress formation. A statistical analysis based on a 24 factorial design revealed that increasing residual compressive stress on the surface was achievable by increasing the coefficient of thermal expansion and modulus of elasticity, as well as the viscosity, while reducing the effective thermal diffusivity. Finally, a mathematical model was proposed to relate the thermomechanical properties of the ceramic material to the residual stresses observed on the surface following thermal tempering.

Evaluation of Marginal Accuracy and Microstructure of Heat Pressed Lithium Disilicate and Zirconia Reinforced Lithium Silicate Crowns after Thermal Tempering

Evaluation of Marginal Accuracy and Microstructure of Heat Pressed Lithium Disilicate and Zirconia Reinforced Lithium Silicate Crowns after Thermal Tempering

FATIGUE BEHAVIOUR OF TEMPERED AND ISOTHERMAL HEAT TREATED AISI 5160 LEAF SPRING STEEL

The oil quench and temper technique have a lot of benefits for heavy duty spring manufacture since it may expose the best balance of toughness and ductility, as well as increase fatigue life. The current study looked at the fatigue behavior of tempered AISI 5160 leaf spring steel samples at tempering temperatures of 400, 450, 500, 550, and 600 °C, as well as isothermally heat- treated steel samples at 830 °C. All leaf spring steel samples that had undergone thermal tempering and isothermal heat treatment were then tested up to fracture utilizing rotational fatigue test equipment under the effect of various stress levels. All steel samples subjected to tempering heat treatments of 400°C to 600°C showed a decrease in hardness ratings. The Rockwell hardness ratings of the steel samples that treated to isothermal heat treatment increased significantly. Experimental fatigue testing revealed that the values of fatigue resistance for steel samples tempered at (400 and 450) °C temperatures dropped by a small amount. The fatigue resistance values for steel specimens tempered at 500 °C to 600 °C temperatures decreased more than the values for steel samples tempered at 500 to 600 °C temperatures. A fatigue resistance of steel samples that were treated to isothermal heat treatments, on the other hand, increased. Steel samples that were isothermally heat-treated at 830 °C and then chilled in a salt brine solution, on the other hand, showed an increase in fatigue resistance

The Effect of Thermal Tempering on Fracture Resistance and Surface characterization‏ of Lithium Disilicate and Zirconia Reinforced Lithium Silicate Crowns

The Effect of Thermal Tempering on Fracture Resistance and Surface characterization‏ of Lithium Disilicate and Zirconia Reinforced Lithium Silicate Crowns

Further Investigations and Parametric Analysis of Microstructural Alterations under Rolling Contact Fatigue.

Bearing elements under rolling contact fatigue (RCF) exhibit microstructural features, known as white etching bands (WEBs) and dark etching regions (DERs). The formation mechanism of these microstructural features has been questionable and therefore warranted this study to gain further understanding. Current research describes mechanistic investigations of standard AISI 52100 bearing steel balls subjected to RCF testing under tempering conditions. Subsurface analyses of RCF-tested samples at tempering conditions have indicated that the microstructural alterations are progressed with subsurface yielding and primarily dominated by thermal tempering. Furthermore, bearing balls are subjected to static load tests in order to evaluate the effect of lattice deformation. It is suggested from the comparative analyses that a complete rolling sequence with non-proportional stress history is essential for the initiation and progression of WEBs, supported by the combination of carbon flux, assisted by dislocation and thermally activated carbon diffusion. These novel findings will lead to developing a contemporary and new-fangled prognostic model applied to microstructural alterations.

The effect of two thermal tempering protocols on the surface roughness of heat-pressed lithium silicate ceramics

The effect of two thermal tempering protocols on the surface roughness of heat-pressed lithium silicate ceramics

Correction to: Influence of an Amide-Functionalized Monomeric Unit on the Morphology and Electronic Properties of Non-Fullerene Polymer Solar Cells

A straightforward competent strategy to attune the solid-state morphology, opto-electronic and photovoltaic properties of conjugated co-polymers has been studied by inserting different percentages of N,N-dimethylthiophene-3-carboxamide (TDM) monomeric units. The TDM percentage was varied from 20 to 100%, resulting in widening of the energy band gap. Fabrication of solar cells was performed with ITIC-4F as an electron acceptor to accomplish power conversion efficiencies (PCEs) of 7.8% for P4 (minimum TDM) and 0.85% for P1 (maximum TDM) under a thermal tempering process. A drastic drop in the PCE was noted with increasing percentage of TDM which agrees well with the optical, electronic, and morphological studies. Morphological analysis revealed high crystallinity for P4:ITIC-4F blend having minimum percentage of TDM units compared to its counterparts of higher TDM percentages. A sharp increase in π-π stacking is seen with reduced percentage of TDM units, leading to d spacing of 3.6 A. Detailed investigations regarding the charge carrier transport in relation to the π-π stacking of the polymeric film are well implemented in this work.

Differences in indentation and wear behaviors between the two sides of thermally tempered soda lime silica glass

AbstractThermal tempering is an industrial process widely used to make soda lime silica (SLS) glass panels stronger and tougher. During the tempering process, the upper and bottom sides of the glass may experience different cooling rates, and thus, their properties could be different. This study characterized changes in surface composition and subsurface glass network structures as well as indentation and wear resistance properties of the air‐ and tin‐sides of 6‐mm‐thick SLS window panels faced toward the upper and sliding roller sides during thermal tempering. The results showed that although the chemical and structural differences detected with X‐ray photoelectron spectroscopy and specular reflection infrared spectroscopy are subtle, there are large differences in nanoindentation behaviors and mechanochemical wear properties of the SLS glass surface. The findings of this study provide further insights into the performance difference between the air‐ and tin‐sides of the SLS glass panel treated with thermal tempering.

Thermal Tempering Does Not Increase the Survival of Eyed Salmonid Eggs

Eyed salmonid eggs can be subjected to large temperature swings during development, particularly when shipped in ice-filled containers from broodstock facilities to production hatcheries. This study examined the effect of thermal tempering on the survival of brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss eyed eggs to hatch. Eyed eggs at 1°C were either directly placed in 11°C water or allowed to thermally temper from 1°C to 11°C gradually over an hour. In addition, each of the tempering treatments occurred either with or without a 10-minute iodophor disinfection treatment. Tempering had no significant effect on survival-to-hatch in either species (85% - 97%). However, survival was significantly lower in rainbow trout eggs subjected to iodine disinfection (73% - 75%) compared to non-disinfected eggs (91% - 97%), likely because of the close proximity to hatch. The results of this study indicate that slowly raising the temperature (thermal tempering) of brown trout and rainbow trout eyed eggs is unnecessary. Additionally, iodine disinfection of eyed salmonid eggs in close proximity to hatching should be avoided.

Improved reliability of mechanical behavior for a thermal tempered lithium disilicate glass-ceramic by regulating the cooling rate

Traditional thermal tempering was applied to lithium disilicate (LD) glass-ceramic specimens with bar-like and disc-like shapes. The tempering process was conducted by heating the specimens to a temperature below the dynamic softening point, and then rapid cooling in silicone oil with different temperatures ranging from room-temperature to 300 °C to regulate the cooling rate. Effect of the oil-temperature on mechanical behavior of the tempered glass-ceramic was investigated. For the tempering at the lower oil-temperature (e.g., at room-temperature), it was found that the LD glass-ceramic specimens with both the bar-like and disc-like shapes could be remarkably strengthen and toughen, however, obvious anisotropy in fracture toughness was displayed by the specimens with the bar-like shape. With increasing the oil-temperature up to 250 °C, the mechanical anisotropy of the bar-like specimens could be significantly alleviated without much loss of the strengthening effect. The results can provide references for improving reliability of mechanical behavior for the tempered LD glass-ceramic by regulating the cooling condition according to specimen geometry.

Flexural Strength of Different Monolithic Computer-Assisted Design and Computer-Assisted Manufacturing Ceramic Materials upon Different Thermal Tempering Processes.

Objective Strength of ceramics related with sintering procedure. This study investigated the influence of different tempering processes on flexural strength of three monolithic ceramic materials. Materials and Methods Specimens were prepared in bar-shape (width × length × thickness = 4 × 14 × 1.2 mm) from yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP, inCoris TZI [I]), zirconia-reinforced lithium silicate (ZLS, Vita Suprinity [V]), and lithium disilicate (LS 2 , IPS e.max CAD [E]), and sintered with different tempering processes: slow (S), normal (N), and fast (F) cooling procedure ( n = 15/group). Flexural strength (σ ) was determined using three-point bending test apparatus at 1 mm/min crosshead speed. Statistical Analysis The analysis of variance and Bonferroni’s multiple comparisons were determined for significant difference (α = 0.05). Weibull analysis was applied for survival probability, Weibull modulus (m), and characteristics strength (σ o ). Microstructures were evaluated with scanning electron microscope and X-ray diffraction. Results The mean ± standard deviation (MPa) of σ, m, and σ o were: 1,183.98 ± 204.26, 6.23, 1,271.80 for IS; 1,084.43 ± 204.79, 5.76, 1,170.08 for IN; 777.19 ± 99.77, 8.78, 819.96 for IF; 267.15 ± 32.71, 9.11, 281.48 for VS; 218.43 ± 38.46, 6.40, 234.23 for VN; 252.67 ± 37.58, 7.20, 269.23 for VF; 392.09 ± 37.91, 11.37, 409.23 for ES; 378.88 ± 55.38, 7.45, 403.11 for EN, and 390.94 ± 25.34, 16.00, 403.51 for EF. Thermal tempering significantly affected flexural strength of Y-TZP ( p < 0.05), but not either ZLS or LS 2 ( p > 0.05). Y-TZP indicated significantly higher flexural strength upon slow tempering than others. Conclusion Enhancing flexural strength of Y-TZP can be achieved through slow tempering process and was suggested as a process for monolithic zirconia. Strengthening of ZLS and LS 2 cannot be accomplished through tempering; thus, either S-, N-, or F- tempering procedure can be performed. Nevertheless, to minimize sintering time, rapid thermal tempering is more preferable for both ZLS and LS 2 .

Flexural strength improvement for structural glass: a numerical study

Glass is generally known as a fragile material. It is sensible to the cracks created from manufacturing or contact damage. The strength of a perfect glass without crack could reach 10 GPa. By mean of strengthening such as thermal tempering, glass can be safely use for building as architectural elements and very limited to the structural elements. The authors have been developing glass strengthening methods and structural design for large scale glass beam. Some influencing factors are considered: material, premature crack effect, geometry of sample and bolt. The mechanical behaviour of glass is modelled as elastic-plastic material, which show significant results in glass-bolt contact problem. The crack length, size and position provide information of a critical angle that allow to govern the crack effect in the beam connection.

Thermal Tempering Does Not Impact Rainbow Trout and Brown Trout Survival

Hatchery-reared fish are frequently adjusted (tempered) to the higher water temperatures present in the water bodies where they are to be stocked. This study was undertaken to determine the necessity of such tempering practices. This study used rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) reared at 11.2°C. The first two trials for each species were designed to simultaneously determine the upper incipient lethal temperature and 100% lethal temperature over a 14-day period. The third trial for each species evaluated the effects of an exaggerated 12-hour tempering regime on fish survival after placement in elevated water temperatures. After transfer from a water temperature of 11.2°C, no rainbow trout survived at 26°C, and only 50% survived at 25°C. No brown trout survived at 22°C and only 50% at 20°C. Survival of rainbow trout was not improved by the 12-hour tempering regime where water temperatures were slowly increased from 11.2°C to either 25°C or 26°C. Similarly, tempering did not improve brown trout survival at either 20°C or 22°C. These results suggest that tempering is not needed when hatchery-reared trout are reared and stocked at the water temperatures within the range of those used in this study.

Dipolar spin glass transition in three dimensions

Dilute dipolar Ising magnets remain a notoriously hard problem to tackle both analytically and numerically because of long-ranged interactions between spins as well as rare region effects. We study a new type of anisotropic dilute dipolar Ising system in three dimensions [Phys. Rev. Lett. {\bf 114}, 247207 (2015)] that arises as an effective description of randomly diluted classical spin ice, a prototypical spin liquid in the disorder-free limit, with a small fraction $x$ of non-magnetic impurities. Metropolis algorithm within a parallel thermal tempering scheme fails to achieve equilibration for this problem already for small system sizes. Motivated by previous work [Phys. Rev. X {\bf 4}, 041016 (2014)] on uniaxial random dipoles, we present an improved cluster Monte Carlo algorithm that is tailor-made for removing the equilibration bottlenecks created by clusters of {\it effectively frozen} spins. By performing large-scale simulations down to $x=1/128$ and using finite size scaling, we show the existence of a finite-temperature spin glass transition and give strong evidence that the universality of the critical point is independent of $x$ when it is small. In this $x \ll 1$ limit, we also provide a first estimate of both the thermal exponent, $\nu=1.27(8)$, and the anomalous exponent, $\eta=0.228(35)$.

Tempering potential-based evaluation of the courtyard microclimate as a combined function of aspect ratio and outdoor temperature

Courtyards are traditional construction models in Mediterranean cities. In this research, tempering performance of courtyards during a two-year field monitoring campaign in southern Spain was investigated. The main objective was to identify the thermal functions of inner courtyards, analyzing the aspect ratio (AR) and the influence of outdoor temperature to offer a perspective that contributes to the development of passive cooling strategies for urban housing. This investigation also reviewed these climate modifiers, in light of the average lifespan of a building, to establish thermal tempering guidelines to mitigate the effects of climate change. The results show that, although the AR is a determining factor in maximizing the courtyard tempering potential, other parameters such as diurnal temperature range (DTR) or maximum outdoor temperature (MOT) can significantly modify the influence of the AR. The study demonstrates these interactions verifying, for the climates studied, that courtyards with AR > 3 are appropriate solutions, especially in the warmest zones, enhancing microclimate management in summer. Results evince that courtyard maximum thermal performance is related to MOT increase. This factor is crucial to establish a tempering initial potential for a given courtyard. Apart from this, a complete daily cycle analysis through DTR confirms and clarifies this thermal buffer effect.

Investigation of alumina film formed over aluminized RAFM steel by plasma assisted heat treatment

Reduced Activation Ferritic Martensitic (RAFM) steel is currently under intense consideration as a structural material for the blanket applications in fusion reactor. The concept of blanket module utilizes both solid i.e. Li2TiO3 and liquid breeder material, i.e. Eutectic Pb-17Li operating at 320–480 °C. The critical issues like liquid metal corrosion of RAFM steel, tritium permeation into RAFM steel and magneto hydrodynamic drag generation due to flowing Pb–17Li is already reported. αAl2O3 + FeAl coatings have been found promising to mitigate these challenges & reported with a substrate of P91 steels. However, coatings with hot dipping process on RAFM are scarcely reported as RAFM steel is in under development. Hence, an experimental investigation is done to examine the effects of heat treatments to form FeAl with a top layer of Al2O3. In-RAFM steel (9Cr-1.4W-0.06Ta) samples were hot dipped in a molten bath of 93%Al & 7%Si at 730 °C. These hot dipped samples were subjected to various heat treatments in 3 different routes. In the 1st route, normalizing heat treatment has been carried out at 980 °C for 30 min followed by thermal tempering in a muffle furnace at 760 °C for 90 min. 2nd route consists of plasma tempering along with normalizing in which O2 was used at low pressure (5 mbar) at 760 °C/90 min with pulsed DC at −520 V. Whereas in the third route, to form α-Al2O3, plasma assisted heat treatments were conducted directly without normalizing up to 24 h. The transformations of these phases have been analyzed through X-ray diffraction. Moreover, to confirm Al2O3 coatings, its thickness as well as the case depth of diffused FeAl, cross-sections of coated samples were investigated by mapping through SEM equipped with energy dispersive x-rays. Among these heat treatments, α-Al2O3 + FeAl formation with a thickness of ∼60–70 μm was observed in route 2. Route 1 resulted in to the formation of θ-Al2O3 + FeAl while route 3 indicated less diffusion of Al in to the substrate with defects.

Influence of different veneering techniques and thermal tempering on flexural strength of ceramic veneered yttria partially stabilized tetragonal zirconia polycrystalline restoration.

BackgroundDifferent technique for ceramic veneering and thermal tempering process are expected to be a reason for alteration in strength of ceramic veneered zirconia. This study evaluates the effect of different veneering technique and varied thermal tempering process on flexural strength of ceramic veneered zirconia.Material and MethodsCeramic veneered zirconia bars (25 mm length, 4 mm width, 0.7&1.0mm of zirconia & ceramic thickness) were prepared from zirconia block (e.max® ZirCAD), sintered at 1500°C for 4 hours, and veneered with ceramics with different techniques including CAD-fused using e.max CAD® (C), Pressed-on using e.max® Zirpress (P), and layering using e.max® ceram (L), with different tempering process through fast (F), medium (M), and slow (L) cooling (n=15). The specimens were determined for flexural strength on a universal testing machine. ANOVA and Bonferroni’s multiple comparisons were used to determine for significant difference (α=0.05). Weibull analysis was applied for survival probability, Weibull modulus (m), and characteristics strength (σc). The interfaces were microscopically examined. The phase transformation of zirconia was determined using X ray diffraction.ResultsThe mean±sd (MPa), m, σc of flexural strength were 922.06±83.45, 12.78, 958.32 for CF, 924.26±74.64, 14.28, 959.62 for CM, 930.25±92.42, 11.83, 970.83 for CS, 518.29±59.97, 10.11, 542.97 for PF, 516.50±67.51, 8.75, 539.17 for PM, and 520.51±42.38, 14.59, 544.51 for PS, 604.36±64.09, 11.28, 630.67 for LF, 583.81±56.95, 11.67, 609.81 for LM, 547.33±52.23, 12.19, 569.36 for LS. The flexural strength was significantly affected by veneering technique (p<0.05). No significant effect on flexural strength upon tempering process was evidenced (P >0.05). Phase transformation from t→m related with veneering and tempering procedure.ConclusionsStrength of ceramic veneered zirconia associated with different veneering techniques, but not directly related with tempering process. CAD-on ceramic veneering zirconia is benefit for enhancing the strength of ceramic bilayer and was recommended as a method for ceramic veneering zirconia. Key words:CAD-CAM, cooling process, flexural strength, thermal tempering, zirconia.

Influence of thermal tempering processes on color characteristics of different monolithic computer-assisted design and computer-assisted manufacturing ceramic materials.

BackgroundThe optical properties of dental restoration were influenced by the sintering parameters. This study investigated the effects of different tempering processes on optical properties of three monolithic Cad-Cam ceramics.Material and Methods135 monolithic material bars (4 mm width, 14 mm length, 1.2 mm thickness) were prepared from yttria-stabilized tetragonal zirconia polycrystalline (inCoris TZI, I), zirconia-reinforced lithium silicate (Vita Suprinity, V), and lithium disilicate glass (e.max CAD, E) ceramics, with different tempering processes through slow (S), normal (N), and fast (F) cooling (n=15). The color appearance (∆EW), translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) were determined. ANOVA and Bonferroni’s multiple comparisons were determined for significant difference (α=0.05). The grain sizes were microscopically examined by scanning electron microscope. The phase transformation of zirconia was determined using X ray diffraction.ResultsThe mean±sd of ΔEW, TP, CR, OP were 74.15±0.46, 1.26±0.15, 0.977±0.006, 1.02±0.12 for IS; 74.00±0.83, 1.27±0.19, 0.977±0.007, 1.02±0.12 for IN; 74.44±0.64, 1.70±0.08, 0.965±0.003, 1.30±0.07 for IF; 73.35±1.32, 2.44±0.24, 0.958±0.006, 2.10±0.20 for VS; 66.37±0.88, 4.05±0.3, 0.911±0.010, 3.18±0.20 for VN; 67.02±0.65, 3.79±0.17, 0.919±0.006, 3.01±0.13 for VF; 60.01±0.30, 5.53±0.17, 0.821±0.006, 2.71±0.06 for ES; 60.18±0.23, 5.49±0.17, 0.822±0.006, 2.66±0.05 for EN; and 59.82±0.26, 5.36±0.06, 0.826±0.002, 2.64±0.07 for EF. The color parameters were significantly affected by type of materials, tempering processes, and their interactions (p<0.05). Phase transformation from t→m related with tempering procedure for zirconia.ConclusionsRapid thermal tempering process of Y-TZP resulted in larger grain size and t→m phase transformation leading to higher translucency. To achieve optimum translucency, a fast thermal tempering process was suggested for inCoris TZI and IPS e.max CAD, whilst a normal tempering process was recommended for Vita Suprinity. Key words:Color, cooling process, contrast, opalescence, thermal tempering, translucency.

Process Design in the Manufacturing of Pipes for Chemical and Petrochemical Industry

In the present study the influence of vanadium microalloy on kinetics of transformation in medium carbon steel is studied. In order to choose the thermal treatment temperatures at optimal values, the steel transformation points were determined by dilatometric analysis. The bainitic transformation point was obtained under fast cooling conditions. The industrial experiments on the hardening and tempered of steel were performed in five variants of the oil hardening and reversing treatment, with austenitizing temperatures for hardening and the tempered temperature. The steel quality was determined, the influence of the temperature on the microalloyed steel structure with vanadium was highlighted. The mechanical characteristics of the pipes after the thermal hardening and tempering were analyzed after the traction test and the shock break. Electron microscopy analysis on extraction replicas revealed aspects of precipitation, globular constituent after return is finely and uniformly distributed, austenitization at lower temperature, resulted in a finer austenitic grain [20]. The finer structure obtained after hardening resulted in heat treatment to return to precipitation of fine and uniformly distributed carbides. It has been found that the influence on bainitic transformation depends on temperature; the steel structure after the quenching and tempering treatment was analyzed by optical and electronic microscopy. The development of welding consumables is permanently challenged with matching the increasing strength and toughness of thermomechanically treated or hardening and tempered steels.

Experimental Study of the Effectiveness of the Vibromechanical Stabilization of Bearing Rings

The paper provides the comparison of vibromechanical technology for stabilization of bearing rings and thermal tempering on the following parameters: performance, energy consumption, and magnitude of residual stresses after treatment. To assess the effectiveness of residual stress relaxation through the usage of vibromechanical energy, there were conducted experimental studies on a specially designed and manufactured prototype of the equipment. The results of experimental studies show that the energy consumption during vibromechanical stabilization is ten times less, and performance is several times higher than during the thermal tempering. Moreover, vibromechanical stabilization allows more effective residual stresses relaxation. The costs for capital investment can be reduced, as the cost of equipment for vibromechanical stabilization is ten times less than the cost of electric furnaces.