VT6 Titanium Alloy Research Articles

Tribotechnical properties of experimental hard alloys with modified cobalt binder

Introduction. This paper discusses tribomechanical characteristics of experimental hard alloys with a modified cobalt binder under friction without lubrication on hard-to-cut materials – stainless steel and titanium alloy. The research objective is to evaluate the process of friction interaction for each friction pair according to a number of parameters, and to determine the optimal combinations of “experimental hard alloy – structural material” on the basis of the established tribological indicators.Materials and Methods. Tribological tests of hard alloys were carried out using a cylinder-to-disc friction scheme for different sliding speeds and temperatures under constant load without the use of lubricants. Comparison of the friction interaction process was carried out by the frictional force, volumetric wear and roughness of the friction tracks on the counterbody. Stainless steel 12H18N9Т and titanium alloy ВТ3-1 were used as counterbody materials. The resistance of experimental compositions to the abrasive type of wear was determined through measuring the surface dynamic microhardness on a scanning nanohardness tester by analyzing the thickness of the scratches caused by the indenter.Results. According to the results of surface microindentation, the experimental alloys 2.22 (binder 5.65% Co + l.8% Mo + 0.6% Ti) and 2.23 (binder 5.1% Co + 2.7% Mo + 0.61 % Ti) are characterized by the highest microhardness. For these materials, the average scratch width at various forces was minimal. During tribological tests, the best frictional characteristics were recorded for stainless steel in combination with experimental alloy 2.22, and for the friction pair “titanium alloy VT3-1 — hard alloy 2.23”. The friction of this combination of materials was characterized by low friction coefficients with a low level of fluctuations, minimal wear of samples, and changes in the initial microrelief of their surfaces.Discussion and Conclusions. As a result of the research, the optimal friction pairs from the point of view of tribological interaction were established, specifically “titanium alloy VT3-1 — hard alloy 2.23” and “stainless steel 12X18N9T – hard alloy 2.22”. The frictional interaction for these combinations of materials is characterized by minimal volumetric wear, which will contribute to increasing the wear resistance of the tool in the areas of elastic contact on the front and rear surfaces.

Investigations of the quality of wrought semi-finished products from VT9 titanium alloy produced by electron beam melting

The Paton Welding Journal, 2022, №03. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

STRUCTURE OF COMMERCIAL TITANIUM SUBJECTED TO LOW-TEMPERATURE ION NITRIDING

The structural-phase state of commercial titanium of grades ВТ1-00 (VT1-00) and ВТ1-0 (VT1-0) has been studied in the initial state and after various types of low-temperature ion nitriding. In the initial state, the VT1-00 and VT1-0 alloys have a single-phase α-Ti structure with a hexagonal close-packed crystal lattice. The hardness of titanium is 140–150 HV 10. It has been shown that ion-beam nitriding of VT1-00 alloy at low temperatures of 350 and 450 °С leads to the formation of thin (up to 5 μm) nitrogen-hardened layers with a hardness of 160–180 HV 0.05. As a result of ion implantation at temperatures of 500 and 550 °C, a nitrogen-modified layer with a microhardness of 190–220 HV 0.05 is formed in the surface layers of the VT1-00 titanium alloy, containing a solid solution of nitrogen in the α-Ti matrix phase. Nitrogen implantation of the VT1-00 alloy at a temperature of 620 °C leads to the formation of titanium nitrides TiN0.26, ε-Ti2N, η-Ti3N2-x in the surface layer of titanium alloy. The microhardness of VT1-00 titanium treated with nitrogen ions at 620 °C increases to 360 HV 0.05. In the case of ion-plasma nitriding (IPN) of VT1-0 titanium at 550 °C for 5 h, a nitrogen-modified layer up to 20 μm deep is recorded in its surface layer, containing isomorphic phases: α-Ti and titanium nitride TiN0.26. The microhardness of the VT1-0 titanium alloy subjected to IPN is 190 HV 0.01.

Influence of the Titanium Nitride Deposition Duration during Vacuum Ion-Plasma Treatment on the Resistance of Coatings in a Hydrogen Atmosphere

In this work, the insulating properties of nitride coatings against the hydrogen penetration into semi-finished or finished products made of VT6 titanium alloy during hydrogenation annealing have been studied. It has been established that an increase of the duration of titanium nitride deposition for more than 30 minutes leads to the formation of pores and cracks in the coating and, as a consequence, to a decrease in the «protective» properties of such coating. It is shown that during linear gradient structure creation, the nitride coating effectively “protects” alloy from penetration of up to 0.5 wt%. of hydrogen.

Evolution of Phase Composition and Thermal Expansion during Heating of VT23 Titanium Alloy

Changes in thermal expansion during heating of hot-extruded tube made of VT23 titanium alloy (Ti-5.45 Al-4.7 V-2.45 Mo-1.1 Cr-0.7 Fe, wt. %) were analyzed. The volume effect of α→β-transformation, β-transus temperature as well as the volume fraction of α-and β-phase formed during heating were calculated based on the received data of dilatometric analysis. Results obtained were compared to thermodynamic calculations and published data. The change in the CTE value of VT23 alloy upon heating to 975 °C was estimated, and the explanation of different CTE values obtained in the present study and published data was proposed.

Research on end mill vibration in machining of VT9 titanium alloy

The reason for the failure of carbide end mills is the chipping of the cutting edges at the transition from the radius edges to the helix edges on the cylindrical part of the cutter. One of the reasons for the chipping of the cutting edges are the vibrations of the end mills which arise due to the intermittent cutting process and the variability of forces acting on the end mill. The principle of operation of a vibration measuring device is considered which allows vibration measurements to be carried out when milling with an end mill. The main measuring elements of the device are two eddy current sensors that allow measuring the vibration displacement of the milling cutter in two directions perpendicular and parallel to the movement of the longitudinal feed. The device has a compensation sensor that takes into account the influence of related factors, and a sensor for fixing the instantaneous rotation speed of the machine spindle. The milling cutter itself, fixed in a collet chuck, was used as an elastic element of the oscillating system. The data of measuring the amplitude of vibrations during milling of titanium alloy VT9 with a four-tooth and six-tooth end mill are presented. The study of vibrations of end mills included two stages. At the first stage, the influence of milling parameters and modes, as well as milling schemes (up and down milling) on the frequency and amplitude was investigated. At the second stage, measures were worked out to reduce the intensity of vibrations and increase the reliability and durability of the milling cutters. The research results showed lower amplitude values when working with a six-tooth cutter.

Reconstruction of Regression Relationships for Determination of Strength Values for Alloys of Products in Diffusion Welding

The article deals with the problem of obtaining the dependence of the product strength parameter on the welding time, welding temperature and pressure during mechanical tests, leak tests. The relevance of this work is due to the complexity of carrying out field experiments to identify dependencies. In particular, the complexity arises from the duration of diffusion welding and the high cost. Application of the method of regression analysis based on a non-compositional plan of the second order for three factors will allow to restore the dependence of the product strength parameter on the time during which welding was carried out, the temperature at which diffusion welding was carried out or could be carried out and on the applied pressure at which mechanical tests were carried out. In the current study, a non-compositional design of the second order for three factors was used - allowing to restore the dependence of the missing values of the strength of the product. The aim of the research is to improve the quality of mathematical modeling. Application of the proposed approach will make it possible to obtain the strength distribution function depending on time, temperature and pressure using the example of a product made of VT14 titanium alloy and 12X18H10T stainless steel. This will make it possible to obtain optimal parameters for the diffusion welding mode and to improve the quality of the resulting products.

RESISTANCE OF TITANIUM ALLOYS TO CAVITATION WEAR

The wear rate of titanium alloys VT1-0, TC5, VT6, VT14, OT4 under the action of microshocks due to cavitation, which is created in distilled water under the surface of the ultrasonic wave emitter, were determined. It was found that the increase in hardness and improvement of cavitation wear resistancefor these alloys depends on the alloying elements, and is also increased after heat treatment and ion-plasma modification of the sample surface. Although no unambiguous correlation was found between the structural class of the alloys and their cavitation wear. Due to ion-plasma modification of alloys, the cavitation wear resistanceis increased by several times, in particular, the VT6 alloy by 3 times. The phase composition of the samples before and after ion-plasma modification was studied and it was found that alloy resistance to cavitation significantly depends on it.

Damage-failure transition in VT6 titanium alloy under consecutive dynamic and VHCF loads

The lifetime of VT6 (Ti-6Al-4V) titanium alloy under consecutive dynamic and very-high cycle fatigue loads is studied. The relevance of the problem is determined by the applications to the prediction of the endurance fatigue limit for materials and structural elements of aircraft gas turbine engines experiencing random dynamic effects under flight cycle conditions. The titanium alloy specimens were used to perform High Cycle Fatigue (HCF) and Very High Cycle Fatigue (VHCF) tests on the ultrasonic testing machine, which allows fatigue loading for 108-1010 cycles with amplitude up to several tens of micrometers and frequency of 20 kHz. It is shown that VT6 alloy specimens in the 108 cycle regime subject to dynamic preloading reduces the fatigue strength by 70%. Structural study of the fracture surface for the specimens after consecutive loading was conducted using the profilometry data to identify the roughness scale invariants induced by defects for corresponding areas responsible for the staging of fatigue damage-failure transition. The scale invariants and corresponding lengths were used to formulate the generalized Paris law governing the crack growth in damaged materials.

ДОСЛІДЖЕННЯ ВПЛИВУ ТВЕРДОГО ЗМАЩУВАННЯ НА ПОКАЗНИКИ ПРОЦЕСУ АЛМАЗНОГО ШЛІФУВАННЯ ВІДПОВІДАЛЬНИХ ДЕТАЛЕЙ З ТИТАНОВИХ СПЛАВІВ

Titanium alloys are widely used in military equipment because of theirs excellent physical properties, such as corrosion resistance, heat resistance, fatigue resistance, and high specific strength. However, the hardness and strength of titanium alloy are high, and the coefficient of thermal conductivity is poor, so the cutting performance is poor. The influence of solid lubricant on the parameters of the process of diamond grinding of hard-to-cut material – titanium alloy VT22 was studied. The evaluation was carried out on the basis of the surface roughness parameter Ra and the postcontact temperature Tpc. It has been established that the use of a solid lubricant based on stearic acid (65%) and molybdenum disulfide (35%) reduces the post-contact temperature by 1.4 ... 2.1 times and the roughness by 1.3 ... 1, 6 times in comprising with results under dry grinding conditions. Solid lubricant has an ambiguous effect on the grinding performance of VT22 depending on transverse feed. It may be linked up to state transition of stearic acid and growth its surface activity. The best results on the surface quality with solid lubrication were achieved under grinding with cutting speed Vc = 25 m/s and transverse feed f = 0.005 mm/double pass.

Электронно-пучковая обработка поверхности металлических материалов, изготовленных аддитивным способом

A method for finishing the surface of metal materials manufactured by additive technologies with an intense pulsed electron beam, which can be an alternative to traditional processing methods is presented. The optimal irradiation modes for VT6 titanium alloy specimens produced by metal powder fusion and 308LSi stainless steel specimens produced by electron beam welding are determined. It is shown that the presented processing method leads to a visual decrease in porosity and a multiple decrease in the surface layer roughness (by 20 times (Ra)) of VT6 titanium alloy manufactured by an additive method. The surface roughness of 308LSi stainless steel specimens fabricated by electron beam welding decreases to 2.1 times in the longitudinal direction, to 5.2 times in the transverse relative to the surfacing plane. It is shown that the elemental composition, strength and tribological properties of the specimens do not change during irradiation in optimal modes. Tensile testing of irradiated specimens revealed an increase in tensile strength by 12%, ductility by 10% (VT6) and anisotropy of mechanical properties depending on the direction of tension relative to the surfacing plane (308LSi).

Топологическая оптимизация силового элемента отсека летательного аппарата из металломатричного композиционного материала

At present, in order to increase the weight efficiency of parts and structures of promising aircraft and rocket-space vehicles, various types of additive technologies and topological optimization methods are being actively introduced. Their purpose is a significant reduction in time and financial costs in the manufacture and creation of fundamentally new geometric solutions. The article considers approaches to selecting the geometric parameters of the strength elements of the flight vehicle body made of a metal-matrix composite material based on VT6 titanium alloy, reinforced with a finely dispersed silicon carbide powder, which is produced by direct laser growth technology. On the basis of numerical simulation, the dependences of the metal-matrix composite material physicomechanical and thermophysical characteristics on the volume fraction of silicon carbide have been determined. It was found that the use of a metal-matrix composite material and the optimization of geometric parameters with adaptation to the direct laser growth technology allows reducing the weight of the strength element of the flight vehicle body by more than 30% (depending on the overall dimensions).

Ударная вязкость титанового сплава ВТ6 с ультрамелкозернистой структурой, полученной методом равноканального углового прессования

The wide use of two-phase titanium alloys in aircraft engine building, as well as the intense development of this industry, stipulate more and more stringent requirements to structural materials and the enhancement of their reliability, strength and performance characteristics. The formation of an ultrafine-grained (UFG) state in metals and alloys using severe plastic deformation (SPD) processing enables achieving high strength properties. However, an important aspect of UFG materials is their structural and textural effects which may lead to a strong anisotropy of their properties. In this respect, the authors studied the effect of microstructural features on the mechanical properties and impact toughness of the VT6 alloy after equal-channel angular pressing (ECAP) and subsequent deformation by upsetting, imitating die forging. The study showed that the formation of a UFG structure in the VT6 titanium alloy with a grain size of about 0.4 µm allows increasing the ultimate tensile strength up to 1250 MPa. The additional upsetting of the UFG alloy at T=750 °C leads to grain growth up to 0.5–1 µm and a decline in strength to 1090 MPa as a result of the recovery and recrystallization processes. Impact toughness tests were conducted on specimens with a V-shaped stress raiser at room temperature, showing that the impact toughness of the UFG VT6 alloy was 0.41 MJ/m2. The tests revealed the anisotropy of impact toughness in the UFG VT6 alloy after equal-channel angular pressing and additional upsetting due to the metallographic and crystallographic texture formed as the result of deformation treatment. In test direction No. 1, the impact toughness value is the lowest and equals 0.31 MJ/m2.

Модификация поверхности карбидовольфрамового композиционного материала методами электронно-ионно-плазменного воздействия

The surface of a porous tungsten carbide pseudoalloy of the WC-WCoNiFe system has been modified by a pulsed electron beam and the method of combined electron-ion-plasma, which includes vacuum arc deposition of a film from VT1-0 titanium alloy (1 μm) and subsequent pulsed electron-beam processing of the"coating/substrate" system. Optimal modes of pulsed electron-beam processing were found depending on the energy density in the pulse (40-65 J/cm2) and the pulse duration (150-200 µs). It is shown that electron-beam surface treatment of a material of this class under optimal conditions of electron-beam processing makes it possible to increase the microhardness of the surface layer by 15% relative to the initial material. Using the methods of X-ray phase analysis, it was revealed that the increase in microhardness is due to the formation of the W2C phase in the surface layer and a decrease in the amount of the binder (WCoNiFe). It is concluded that the combined electron-ion-plasma treatment of a porous tungsten carbide pseudoalloy of the WC-WCoNiFe system makes it possible to form a modified layer with a minimum number of pores and cracks on the surface.

Исследование структуры и коррозионной стойкости титановых сплавов, полученных методом электроимпульсного (искрового) плазменного спекания

The results of the structure and corrosion resistance researches of titanium alloys VT1-0, PT-3B and VT6 obtained by spark plasma sintering (SPS) are described. Microstructure, phase composition and microhardness have been investigated. It is shown that the alloy samples have a homogeneous high-density microstructure and high values of microhardness. The alloys samples showed high corrosion resistance in the electrochemical corrosion tests in acidic aqueous solution causing intergranular corrosion. The alloys also showed high resistance against hot salt corrosion. It has been suggested that the high hardness of the alloys as well as the differences in corrosion resistance of the central and lateral surfaces of the samples are due to the diffusion of carbon from the graphite mold into the sample surface.

Исследование защитных свойств покрытий, полученных методом микродугового оксидирования в щелочных растворах электролитов

The article presents the results of a study of the corrosion properties of oxide coatings compacted with polymers and without compaction. Oxide coatings were obtained on VT1-0 and VT5 titanium alloys under the influence of fast pulsed actions of the micro-arc oxidation (MAO) process. To form MAO coatings, a pulsed mode of the process was used with an anodic current pulse duration of 250 ± 25 μs; the cathodic current pulse duration of 5 ± 0.5 ms; pause between anodic and cathodic current pulses 250 ± 25 μs; repetition rate of anodic and cathodic pulses 50 ± 0.5 Hz. Alkaline solutions were used as electrolytes. Fluoroplastic and epoxy resin solutions were used to seal the oxide coatings. The obtained MAO coatings have 4.4 – 7.5 % porosity on the VT1-0 alloy and 5.4 – 12.1 % on the VT5 alloy. The average diameter of oxide coating pores varies from 0.1 to 0,5 µm. X-ray phase analysis showed titanium dioxide in anatase and rutile modification in the oxide coatings composition. Tests performed in a 24 % solution of sulfuric acid at 40 and 75°C showed that the coatings on the VT1-0 alloy, both oxide and oxide-polymer, are more corrosion resistant than similar coatings on the VT5 alloy. All types of coatings produced on VT1-0 alloy are corrosion-resistant at a test temperature of 40 °C. Consolidation of MAO coatings with polymeric materials improves corrosion properties.

Microstructure and Mechanical Properties of Titanium Alloy VT6 and VT20L Diffusion Joints

Microstructure and Mechanical Properties of Titanium Alloy VT6 and VT20L Diffusion Joints

Composition of surface layers of titanium VT6 alloy after implantation of tantalum ions

The paper presents the results of the investigation of the surface layer composition of titanium alloy VT6 obtained after ion implantation with tantalum ions. It is shown that tantalum ion implantation can lead to a significant reduction in surface roughness, as well as a beneficial effect on the corrosion properties of the titanium alloy.

Влияние состава электролита на процесс электролитно-плазменного полирования титановых сплавов

Electrolyte-plasma polishing (EPP), also known as electrolyte-plasma treatment (EPT) has become widespread in industry as an alternative to traditional chemical, electrochemical and mechanical methods of improving the surface quality of products made of metallic materials. EPP is an innovative technology used to obtain metal surfaces with low roughness and a high gloss. Electrolyte-plasma polishing is widely used in aerospace, biomedical, precision instrumentation and other. This work is devoted to the study of the effect of the electrolyte composition on achieving the effect of polishing titanium alloys during the implementation of the EPP process. The studies were carried out on the example of polishing a titanium alloy VT6 (Ti – 6 Al – 4 V) in a three-component aqueous electrolyte containing NaF, NH2OH·HCl and KCl. It was shown that, depending on the concentration ratio of NaF and NH2OH·HCl protolyte salts, either the formation of oxide films or their anodic dissolution in the presence of a ligand can be observed on the treated surface, with the production of a clean, non-anodized metal surface, accompanied by a decrease in roughness (polishing effect). It is established that the polishing effect is achieved at a certain ratio of NaF and NH2OH·HCl, which ensures the formation of hydrogen fluoride in it in an amount sufficient to dissolve the oxide films formed on the treated surface.

ХАРАКТЕРИСТИКИ ПРОЧНОСТИ И ВЫНОСЛИВОСТИ ПРУТКОВ И ШТАМПОВОК ЛОПАТОК ИЗ СЕРИЙНЫХ ЖАРОПРОЧНЫХ ТИТАНОВЫХ СПЛАВОВ И НОВОГО ТИТАНОВОГО СПЛАВА ПСЕВДО-α-КЛАССА

Presents the microstructure and mechanical properties of bars and blade forgings made of new heat resistant titanium alloy. A typical microstructures of studied industrial alloys were demonstrated. The main clue of the article is noted to fatigue stability of bars and forgings material. The analysis of strength and impact toughness of bars and blade forgings made of industrial titanium alloys VT3-1, VT8, VT8M-1, VT9, VT20 were carried out in comparison with new heat-resistant titanium near- alloy.