High Temperature Strength Properties Research Articles

Effects of longitudinal ultrasonic vibration on tool wear behaviors in side milling of GH4169D superalloy

The GH4169D superalloy, a novel Nickel-based material widely acknowledged for its exceptional high temperature strength and fatigue resistance properties, plays a pivotal role in the production of critical components of contemporary aero-engines. The material, however, falls under the category of a typical difficult-to-cut metallic material due to the substantial cutting forces and significant tool wear experienced during the machining process. In this paper, a method of longitudinal ultrasonic vibration assisted side milling (LUVM) was developed to extend tool life. The investigation primarily involved an analysis of tool wear behaviors, including milling force, tool life, morphologies of tool wear, and various underlying wear mechanisms in LUVM and conventional milling (CM) of GH4169D superalloy. The results demonstrate that LUVM exhibits the advantage of reducing milling forces and prolonging tool life in comparison to CM. Throughout the entire milling process, the maximum milling force of LUVM is consistently smaller than that of CM, displaying a comparatively slower growth trend. At the conclusion of machining, while CM reaches a maximum milling force of 360.3 N, the maximum milling force of LUVM (195.9 N) is significantly lower. The tool life of LUVM is 28.2 min, representing a 33 % increase compared to CM (21.2 min). Material adhesion, coating delamination, and built-up edge (BUE) phenomena can be observed on both the tool rake face and flank face in CM. LUVM contributes to mitigation of bonding phenomena, prevention of BUE formation, and avoidance of abrasive wear in comparison to CM. However, it is prone to lead to tool tip chipping. For CM, the tool wear mechanisms include adhesive wear, oxidation wear, abrasive wear and diffusion wear; whereas for LUVM, the tool wear mechanisms comprise of adhesive wear, oxidation wear and diffusion wear.

Development of Creep and Mechanical Properties for SMAW Cr-Mo-X Steel Welds

This research describes the development of new welding materials with high strength and high heat resistance for Cr-Mo-X type steels. Through thermodynamic simulation, the newly designed welding electrode had excellent mechanical properties, especially in high temperature tensile testing at 600℃ with 393.2 MPa tensile strength, 385.3 MPa yield strength and 23.5% elongation. Refinement of second phase particles were key to the success of the newly designed electrodes. Presence of M<sub>23</sub>C<sub>6</sub> is noticeable in the new electrode welds which contributed to the high temperature strength and creep properties. Compared to conventional products, it was confirmed that the amount of M23C6 precipitates, measured in area fraction, increased substantially, from 5.9 to 11.9%. Z-phase, known to degrade weld mechanical properties, was reduced through adjusting chemical composition of the experimental welds. The reduction in Z-phase precipitates improved the brittle fracture resistance.

High-Temperature Bending Tests of Reaction-Sintered Silicon Carbide-Based Ceramic Materials

The high-temperature strength properties of silicon carbide-based ceramic materials reaction-sintered in air and vacuum are proved by experimental data. The ultimate bending strength of pressed and cast ceramic material samples at temperatures up to 1400°C was measured as a criterion. High-temperature tests demonstrate the guaranteed strength of ceramics above 100 MPa. An example of the manufacture of a complex shaped ceramic product using the hot slip casting processing under pressure into additive water-soluble forms is given. An approval of the combined technology makes it possible to manufacture bladed ceramic elements with a thickness of about 1 mm.

Effect of temperature on thermal properties and residual strength of coal gangue concrete

Key factors for assessing the high-temperature resistance of coal gangue concrete are high-temperature residual strength and thermal properties. The high-temperature residual strength, high-temperature thermal conductivity, high-temperature specific heat capacity, and high-temperature density of concrete with various coal gangue coarse aggregate replacement ratios were tested using experimental methods in this paper to study the high-temperature resistance of coal gangue concrete. Thermal density and high-temperature residual strength tests took into account influencing factors like the water-cement ratio (0.50, 0.45, 0.40), aggregate replacement ratio (0, 25 %, 50 %, 75 %, 100 %), and temperature variation (room temperature, 200 °C，300 °C，400 °C，500 °C，600 °C，700 °C，800 °C), while thermal properties tests considered the effects of various coarse aggregate replacement ratios and temperatures. The study showed that when the temperature rises, coal gangue concrete's thermal density falls, mass loss rises, residual strength declines, thermal conductivity rises, and its specific heat capacity fluctuates. At temperatures between 20 °C and 400 °C, concrete's residual strength decreases with an increase in the coal gangue coarse aggregate replacement ratio, while thermal conductivity and specific heat capacity increase. At temperatures between 500 °C and 800 °C, however, concrete's residual strength slightly improves with an increased coal gangue coarse aggregate replacement ratio, while mass loss changes more. The research finally provides the formulae for calculating the high-temperature residual strength and thermal properties of coal gangue concrete based on the test results.

Controlling the addition of solute Ti in Al-Mg-Zn-Cu-Ni alloy for enhanced high-temperature creep properties

This study aims to fundamentally understand the effect of 0.1 at% Ti addition (for introducing solute Ti with low diffusivity into the α-Al matrix) on the microstructure and high-temperature mechanical performance of a heat-resistant Al–5Mg–3.5Zn–2Cu–2Ni (at.%) quinary alloy subjected to heat treatments. The precipitation morphologies of the T-Al6Mg11Zn11 phase are systematically characterized in terms of the distribution of solute Ti, which is controlled by a peritectic reaction during solidification. High-temperature strength and creep properties (200 °C/105 MPa) are examined using the Ti-added alloy specimen and compared with the results of Ti-free quinary alloy specimens. In the Ti-added alloy, solute Ti is distributed within the dendritic α-Al phases formed through the peritectic reaction. The precipitation morphologies vary depending on solute Ti contents in the α-Al matrix after isothermal aging at 200 and 300 °C. Numerous fine T-phase precipitates are homogeneously dispersed in the α-Al matrix containing high solute Ti content. Fine precipitation morphologies appear stable even after long-term exposure at 200 °C. Ti addition extends creep rupture life (at 200 °C) without the loss of static high-temperature strength and room-temperature ductility. The improved creep properties could be responsible for the reduction in creep rate by the refined precipitation morphologies in the α-Al matrix containing higher solute Ti contents. Local coarsening of the precipitates occurs owing to the solute Ti during creep (under stress). The mechanism is discussed in terms of the effect of Ti addition on the phase equilibria between the α-Al and other intermetallic phases.

Effect of He Plasma Exposure on Recrystallization Behaviour and Mechanical Properties of Exposed W Surfaces—An EBSD and Nanoindentation Study

Fusion reactors are designed to operate at extremely high temperatures, which causes the plasma-facing materials to be heated to 500 °C to 1000 °C. Tungsten is one of the target design materials for the plasma-facing diverter components in Tokamak designs, such as ITER, because of its excellent high-temperature strength and creep properties. However, recrystallization due to high temperatures may be detrimental to these superior mechanical properties, while exposure to He plasma has been reported to influence the recrystallization behaviour. This influence is most likely due to the Zener effect caused by He bubbles formed near the surface, which retard the migration of grain boundaries, while at the same time modifying the surface microstructure. This paper reports a study of the effect of plasma exposure at different sample temperatures on the recrystallization behaviour of W at different annealing temperatures. The characterization after plasma exposure and annealing is pursued through a series of post-exposure annealing, followed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) characterization and nanoindentation to determine the mechanical properties. Here, it is shown that the hardness is closely related to the recrystallization fraction, and that the plasma exposure at a sample temperature of 300 °C slows down the recrystallization more than at higher sample temperatures of 500 °C and 800 °C. Atomic force microscopy (AFM) was subsequently used to determine any changes in pile-up height around the nanoindents, to probe any indication of changes in hardenability. However, these measurements failed to provide any clear evidence regarding this aspect of mechanical behaviour.

Influence of the γ′ Volume Fraction on the High-Temperature Strength of Single Crystalline Co–Al–W–Ta Superalloys

Understanding the influence of γ′ and secondary-phase fractions on the mechanical properties of superalloys is very important to optimize these high-strength materials. So far, this has not been systematically investigated for the novel class of Co-based superalloys. In this study, a Co–Al–W–Ta model alloy series was designed with compositions of γ/γ′ on the tie-line and an increasing γ′ volume fraction of up to 70% after heat treatment at 900 °C, while a few alloys are unexpectedly out of γ/γ′ two-phase region with an additional secondary phase fraction of up to 15%. The high-temperature strength and creep properties were evaluated by compression tests up to 1050 °C and compressive creep experiments at 950 °C, respectively. At temperatures of up to 1050 °C, an increasing γ′ volume fraction consistently increased the yield strength, which was not dramatically changed by the presence of secondary phases. Significant work hardening was found in alloys with γ′ volume fractions of 65–70% during compression testing, but not in alloys with either a lower γ′ volume fraction (<50%) or a high fraction of secondary phases (~15%). Similar to the yield strength, the creep strength also increased continuously with the γ′ volume fraction, but was greatly reduced with an increasing fraction of secondary phases. The best creep performance at 950 °C and 200 MPa was found in the alloy with the highest γ′ volume fraction and no secondary phases. At higher creep stresses, rafting contributed significantly to the hardening and, again, the alloy with a high γ′ volume fraction and a small amount of secondary phases exhibited the highest strength.

Effect of Cr3C2 content on microstructure, mechanical and tribological properties of Ni3Al-based coatings

To broaden the applicability of Cr3C2 -reinforced Ni3Al-based coatings, which possess exceptional high-temperature strength and anti-friction properties for high-temperature solid lubrication, this study examined the influence of varying Cr3C2 concentrations (0 wt%, 10 wt%, 15 wt%, and 20 wt%) on the phase composition, microstructure, mechanical performance, and friction and wear behaviors of Ni3Al-based coatings from 25 °C to 800 °C. The findings indicated that decarburization of Cr3C2 took place during HVOF spraying, forming Cr7C3. The remarkable high-temperature lubricity of all coatings can be attributed to the synergistic lubrication effect resulting from the precipitation of soft metal Ag, the brittle-plastic transformation of MoO3, and high-temperature solid lubricants such as NiCr2O4 and Ag2MoO4, which are induced by high-temperature friction. The second phase strengthening of Cr3C2 and the solute effect in the Ni3Al matrix phase significantly improved the hardness and toughness of the coatings, thereby enhancing their wear resistance. Notably, the coating containing 15 wt% Cr3C2 exhibited the lowest coefficients of friction (COFs) and wear rates (WRs) (10−5 mm3·(N·m)−1), ranging from 0.60 to 0.26 and 14.48 to 2.01 at 25 °C to 800 °C, which can be ascribed to the coordination between lubricity and mechanical strength.

Fabrication and high-temperature tribological behaviors of Al2O3/Cr2O3 composites with three-dimensional continuous structure

A new strategy for improving high-temperature compressive strength and tribological properties of Al2O3/Cr2O3 composites was proposed in this study. The three-dimensional (3D) continuous Al2O3 ceramic matrix containing Cr2O3 particles was fabricated, and the influencing mechanisms of compositions and structures on the anti-wear and friction-reducing performance of composites at high temperature were revealed. Results show that the enrichment degree of Cr2O3 in the composites can be significantly improved based on the 3D continuous structure design compared with Al2O3/Cr2O3 composite containing uniform compositions. Under friction conditions, the Cr2O3 phase with large enrichment degree can preferentially contact with the micro-asperities on the friction pair surface under the action of grain refinement at high temperature, so that the softened Cr2O3 is easy to be sheared and dragged to the worn surfaces of the frictioncouples to form the friction film and transfer film. Meanwhile, under the favorable effect of the high load-carrying capacity of continuous Al2O3 matrix, Al2O3/Cr2O3 composites show excellent tribological properties at high temperature. The friction coefficient and wear rate of Al2O3/Cr2O3 composites with 3D continuous structure sliding against Al2O3 pin can be reduced to 0.35 and 2.2 × 10-6 mm3·N-1m−1 at 800 °C, and it still presents excellent friction-reducing and anti-wear properties at 1000 °C.

Phase, mechanical property and corrosion resistance evaluation of W-Nb-Ta-Ti and W-Nb-Ta-Ti-N medium entropy alloy thin films

Multicomponent alloy thin films including high entropy alloy (HEA) and medium entropy alloy (MEA) thin films have drawn lots of attention from researchers and industries because of their outstanding properties, such as high hardness, good wear and corrosion resistance. Among several kinds of multicomponent alloy systems, the refractory HEA and MEA are characterized by their high temperature strength and stable thermal properties. In this work, the W-Nb-Ta-Ti and W-Nb-Ta-Ti-N refractory MEA thin films were fabricated by a magnetron co-sputtering system. The structure of W-Nb-Ta-Ti-N coatings changed from BCC to B1 FCC nitride phase when the nitrogen concentration reached 42.6 at.%. The microstructure of BCC structured W-Nb-Ta-Ti-N thin films changed from a coarse columnar to a dense feature as the nitrogen content increased from 0 to 16.2 at.%. A maximum hardness of 24.4 GPa was obtained for the BCC structured W34.3Nb21.7Ta26.4Ti1.4N16.2 thin film. The best adhesion property and the lowest coefficient of friction were found for the FCC W31.1Nb9.6Ta13.1Ti3.6N42.6 nitride thin film. The corrosion resistance of 304SS substrate in 5 wt% NaCl aqueous solution was greatly enhanced by the deposition of the W-Nb-Ta-Ti and W-Nb-Ta-Ti-N refractory MEA thin films. The best corrosion resistance can be seen for the nitrogen-free W37.9Nb25.8Ta28.8Ti7.5 thin film due to its dense microstructure, highest Ta and Nb contents, high configurational entropy and sluggish diffusion effects.

High-temperature strength properties of epoxy-based adhesive joints and the effects of hightemperature aging

Lap joints were prepared using epoxy adhesive and aluminum plates, and the properties of high-temperature strength were studied. Tensile test and aging test were performed at high temperature. The effects of test temperature were systematically investigated. The obtained conclusions were following. When the specimen was exposed at temperature of 135℃, the strength decreased significantly. The adhesive changed its chemical structure by oxidation. The relationship between test temperature and tensile strength could be expressed using the Arrhenius equation.

Effect of test temperature on the shear and fatigue strengths of epoxy adhesive joints

ABSTRACT Double lap joints were prepared using epoxy adhesive and aluminum plates, and their high-temperature strength properties were studied. Tensile, thermal aging, creep, and cyclic fatigue tests were performed to systematically investigate the effects of the aging temperature, testing temperature, stress waveform, and stress ratio on the strength and fracture morphology of the double lap joints. When the specimen was exposed to 135°C, the strength decreased significantly. Also, the relationship between the test temperature and shear strength could be expressed using an equation obtained from thermal activation theory. Additionally, in the fatigue test at room temperature, the strength of the specimen subjected to constant stress was higher than that of the specimen subjected to cyclic strain. The effect of creep deformation increased in the creep test at high temperatures, and therefore, the strength decreased significantly.

Non-additive sintering of Si2N2O ceramic with enhanced high-temperature strength, oxidation resistance, and dielectric properties

The high-temperature mechanical and dielectric properties of Si2N2O ceramics are often limited by the introduction of a sintering aid. Herein, dense Si2N2O was prepared at 1700 °C by hot-pressing oxidized amorphous Si3N4 powder without sintering additives. A homogeneous network with short-range order and a SiN3O structure was formed in the oxidized amorphous Si3N4 powder during the hot-pressing process. Si2N2O crystals preferentially nucleated at positions within the SiN3O structure and grew into rod-like and plate-like grains. Fully dense ceramics with mainly crystalline Si2N2O and some residual amorphous phases were obtained. The as-prepared Si2N2O possessed a good flexural strength of 311 ± 14.9 MPa at 1400 °C, oxidation resistance at 1500 °C, and a low dielectric loss tangent of less than 5 × 10−3 at 1000 °C.

Study of the Effect of Rhenium on Heat-Resistant Titanium Alloy Mechanical Properties and Microstructure

Complexly alloyed heat-resistant titanium alloys of the composition Ti–5Al–5Mo–5V–3Cr–1Re are studied. High-temperature test mechanical properties of these alloys in compression and tension at 600°C are provided and compared with similar properties of alloy Ti–5Al–5Mo–5V–3Cr. It is established that addition of rhenium increases alloy high-temperature strength properties and plastic deformation processes occur mainly in the β -phase not affecting α -phase.

Phase stability and microstructural evolution of Ti2AlNb alloys-a review

Ti2AlNb alloys are potential next-generation aerospace materials due to their lightweight and high-temperature strength and oxidation resistance properties. Heat treatment of this alloy results in five major microstructures, including fully B2 and α2 + B2, lamellar, bimodal lamellar, equiaxed, and duplex O-phase microstructure. Recently, widmanstätten and plate-like O phase have also been reported. Modern manufacturing methods have made fabrication of high-temperature alloys easy and economical. However, they need post-heat treatments to improve the microstructure and mechanical properties. In this review article, a sequence of various developments in the study of features and thermo-mechanical control on the evolution of various microstructures of the Ti2AlNb intermetallic alloys will be presented. In addition, other aspects such as orientation relationships between different phases, factors affecting grain growth and, phase evolution mechanisms will be discussed. The effect of each heat treatment on every feature of the microstructure will be summarized in each section.

A Method of Producing Al–REE Master Alloys Using Exchange Reduction Reaction

Modern aerospace engineering relies on Al-based alloys with enhanced high-temperature strength properties and oxidation resistance. These requirements can be fulfilled by modifying alloys’ structure employing rare earths metal doping. Direct addition of metallic rare earths to aluminium is complicated due to high chemical activity of molten rare-earth metals and significant vapor pressure of aluminium at elevated temperatures. To overcome these drawbacks, lanthanide-containing master alloys with relatively low REE content can be employed instead of pure scandium.Currently there are three methods for preparing aluminium-based alloys containing rare earths, i.e. direct fusing, molten salt electrolysis and exchange or metallothermic reduction reactions. In the last case, Al–Gd and Al–Sc master alloy can be prepared by aluminothermic reduction of GdF3 or ScF3 in a molten binary NaF–KCl salt mixture at 800–1050 °С.In the present work we suggest the modification of the above mentioned method for aluminium–cerium and aluminium–neodymium master alloy production with a lanthanide concentration of 1 to 7 wt. %. Based on thermodynamic calculations we proposed that the high-temperature exchange reaction between metallic aluminum and corresponding fluoride containing salt electrolyte should be carried out at temperatures from 740 to 780 ° C to provide the higher recovery of REE. The influence of the time of the exchange reaction and «aluminium–salt» ratio on the process to obtain ligatures of various compositions is analyzed. The yield higher than 85 % is achieved.The microstructure of the alloys represents a metal matrix of aluminum in which intermetallic compounds of Ln3Al11 compositions are distributed In the case of an exchange reaction between aluminum and cerium fluoride, the formation of a new phase, presumably related to the Al4Ce intermetallic compound, is found.

Microstructural characterization, mechanical property and corrosion behavior of VNbMoTaWAl refractory high entropy alloy coatings: Effect of Al content

Recently, the refractory high entropy alloy coatings have drawn lots of attention due to their high temperature strength and stable thermal properties. In this study, the VNbMoTaW and three Al contained VNbMoTaWAl refractory high entropy alloy coatings were fabricated using a pulsed direct current magnetron co-sputtering system. Al addition into the VNbMoTaW coatings was chosen for this study since Al is an important material known for its lightweight. The BCC phase of the VNbMoTaWAl coating was kept as 8.54 at.% Al was added. The surface roughness, grain size and density of VNbMoTaW and VNbMoTaWAl coatings decreased with increasing Al content. The addition of Al element into VNbMoTaW coating can increase its hardness up to 18.1 GPa due to the solution hardening effect. The corrosion resistance of the 304 stainless steel substrate in 0.5 M H2SO4 solution was improved by the refractory VNbMoTaW and VNbMoTaWAl coatings. Furthermore, the best corrosion resistance of VNbMoTaWAl coatings was obtained by the addition of 2.37 at.% Al. The equivalent circuit of the VNbMoTaWAl coatings in 0.5 M H2SO4 solution was also proposed. However, the oxygen contamination in excess of 3 at.% in the VNbMoTaWAl coatings had detrimental effects on the mechanical properties and corrosion resistance of the coatings due to formation of oxide phases.

State of art on wire feed additive manufacturing of Ti-6Al-4V alloy

Titanium alloys have high strength to low weight ratio, good creep resistance and high temperature strength properties. Based on these properties, Ti alloys are used as a ‘workhorse’ material in the aerospace industry such as engine blades, landing gear assemblies, large structural parts, airframe and drums etc. Traditional fabrication methods of Ti alloy are expensive and inferior in their mechanical properties. Due to continuous development in science and technology, many researchers have been attracted towards Wire Feed Additive Manufacturing (WFAM) for the fabrication of titanium and its alloys. WFAM has set a new trend by accomplishing the production demand of components from medium to large scale with moderate complexity. This additive manufacturing technology generally employes for high material utilization and higher deposition. This state of art highlights the remarkable achievements of WFAM processes followed by their effect of process parameters, microstructural changes, residual stresses and mechanical properties of Ti-6Al-4V alloy.

Studies on Susceptibility of Alloy 617 to Solidification Cracking

Ni based super alloy 617 is widely used in transition liners in both aircraft and land-based gas turbines, power plant applications because of its high temperature strength, oxidation resistance and creep properties. Ni based alloys are highly susceptible to hot cracking like solidification and liquation racking issues. In this present work, the susceptibility of alloy 617 to solidification cracking is studied based on the varestraint test. Results of this weldability test proved that in addition to the solidification cracking susceptibility alloy 617 is prone to liquation cracking also. Keywords: Varestraint test, Alloy 617, Solidification cracking, Liquidation cracking.

Thermal and corrosion properties of V-Nb-Mo-Ta-W and V-Nb-Mo-Ta-W-Cr-B high entropy alloy coatings

High entropy alloys (HEAs) have drawn lots of attentions from researchers and industries because of their outstanding properties, such as high hardness, and good corrosion resistance. Particularly, the refractory high entropy alloy is characterized by its high temperature strength and stable thermal properties. We conducted the magnetron co-sputtering process to grow one V-Nb-Mo-Ta-W and three V-Nb-Mo-Ta-W-Cr-B refractory HEA coatings. The BCC phase of V-Nb-Mo-Ta-W HEA coating was changed into the amorphous-like structures when Cr and B elements were added into the coatings. Oxidation reactions occurred and very complex refractory metal oxides were produced on all HEA coatings when the oxidation was held at 800 °C in air for 1 h. The addition of Cr and B constituents into the V-Nb-Mo-Ta-W coating can provide good oxidation resistance and anti-corrosion performance. The highest hardness of 18.4 ± 0.5 GPa, an excellent corrosion resistance at room temperature, a high hardness of 15.9 ± 1.1 GPa and good thermal stability after 500 °C oxidation test were obtained for the V10.4Nb10.5Mo10.5Ta11.2W10.5Cr16.3B28.6 refractory HEA coating in this study.