Thermocyclic Treatment Research Articles

Polymorphic transformation: The basis of thermocycling treatment of titanium alloys

1. We have shown that TCT of titanium alloys is based on polymorphic transformations and determined the external and internal factors that affect the results of thermocycling. 2. We have developed the regimes for TCT and subsequent heat treatment for titanium alloys of various structural classes, which diminish the inhomogeneity of the structure and properties of welded junctions. 3. The optimum structure of pseudo-α- and α+β-titanium alloys formed as a result of thermocycling is shown to provide the best combination of mechanical properties of deformable and castable titanium alloys and their welded joints.

Relaxation Processes in Fe-B Metallic Glasses Under Low Energy Laser Treatment

Relaxation processes in Fe 85 B 15 and Fe 75 B 25 metal glasses after pulse laser thermocycling treatment were investigated by means of electroresistance temperature dependence measurement and X-ray powder diffraction method. It has been shown that the laser thermocycling under precrystallization regimes leads to a shift of a glass temperature stability interval toward higher temperatures. Such a shift is due to local topology and composition changes in glasses, which take place after short-term laser heating resulting in formation of clusters with strong thermally stable covalent bonds.

Effect of the preparation conditions upon the stabilization of the superconducting properties of Bi(Pb) SrCaCuO

The present work is devoted to the study of the process conditions for producing Bi-containing high-temperature superconducting (HTSC) materials with sufficiently stable critical parameters and external effects. The sintering of HTSC ceramics under high pressure results in deformation in the 2212 and 2223 phases and internal microstresses. The authors proposed a method for the thermocyclic treatment of HTSC ceramics for restoring the crystal structure of the phases, without altering the elementary cell parameters. The thermogravimetry data studied in static air atmosphere with a heating and cooling rate of 10 deg/min have revealed the insignificant (∼ 0.1% wt) loss of the mass of samples. The main technological parameters for producing highly dispersed chemical and structurally homogeneous powders and Bi-HTSC ceramics have been determined. The process of production of Bi-HTSC ceramics includes the heat treatment of co-precipitated carbonates, the conversion of Ca and Sr carbonates to nitrates and the synthesis of HTSC phase in an O 2-Ar atmosphere. Investigations of the surface and the bulk of HTSC Bi-ceramics by X-ray photoelectron spectroscopy have shown the high homogeneity and stability of this material. No fracture of components was detected after the samples had been kept in air for 6 months.

The effect of thermocycling liquid boronizing on the thickness of the boride layer and the transition zone

Boronizing is a thermo-diffusion surface treatment, which is defined as enrichment of the surface of a workpiece with boron by means of thermo-chemical treatment. The processes are based on chemical or electrochemical reactions between the boron source and the respective base metal. Boron sources or boronizing compounds are solid, liquid or gas. Boride coatings, or the formation of boride compounds near the surface have been achieved by: (a) chemical methods; using gas boronizing agents, by immersion in molten salts, electrolysis and by pack cementation with powders; (b) physical methods; such as boron ion implantation, physical vacuum deposition, sputtering and ion plating. The methods of thermocycling treatment are used for intensification of the diffusion processes and forming more uniform microstructures and grain refinement. Krishtal and Kenis reported that the diffusion processes are accelerated with increasing grain boundary length, vacancy concentration, dislocation density inside the grains, and stress gradients in the thermocycling treatment. In practice, the type of structure favoring the intensification of diffusion processes is obtained using thermocycling treatment (TCT), either as a preliminary treatment before thermo-chemical treatment (TChT) or as a combined process before and during the thermochemical treatment. The steel is usually heated to 30-50 C above Ac[sub 1]more » and cooled to 50-100 C below Ar[sub 1]. Such treatment achieves an increase in the diffusion layer thickness, grain refinement and formation of a polygonal structure in the bulk of the metal. The combined use of TCT and TChT was studied during carburization of steel with a solid carburizer. It was demonstrated that, at the same duration of isothermal treatment (15 h), 5 cycles of 880-750 C, TCT produce grain size No. 5-6 in the bulk and grain size No. 9-10 in the diffusion layer, while the thickness of that layer increases 1.5 times. Improved fatigue resistance was also recorded.« less

Effect of structural parameters on the fatigue failure of cast steels in loading with low-cycle overloads

Experiments were carried out to examine the effect of structural parameters on the fatigue resistance in block loading with elastoplastic (low-cycle) overloads. Differences in the structural parameters were produced by heat treating 20GL steel by different techniques: normalizing, quenching and tempering, thermocyclic treatment (TCT), and by alloying. The results are presented of fractographic and metallographic analysis of specimens subjected to different heat treatments and fractured as a result of fatigue tests. An equation is derived for predicting the fatigue endurance of a specimen in block loading in relation to the mechanical characteristics and structural parameters of the steel.

Thermocyclic high frequency treatment of welded joints in VT22 titanium alloy

Thermocyclic high frequency treatment of welded joints in VT22 titanium alloy

Thermocycling treatment of titanium alloys using hydrogen phase cold working

Thermocycling treatment of titanium alloys using hydrogen phase cold working

Thermocyclic treatment of electron beam welded joints in 12Kh13 chromium steel

Investigations were carried out into the microstructure, hardness and fine structure of different zones of the welded joint: weld, HAZ (at a distance of 1-2 mm from the remelting boundary) and parent metal. In addition, the impact toughness of the welded specimens with a notch in the HAZ was determined

Effect of thermocyclic treatment on the structure and properties of the simulated weld zone of welded joints in 08Kh18G8N2T steel

Effect of thermocyclic treatment on the structure and properties of the simulated weld zone of welded joints in 08Kh18G8N2T steel

Effect of cooling conditions in thermocyclic treatment on the crushing of austenitic steel grain

1. The size of the austenite grain of 20Kh steel depends after TCT on the cooling rate from the temperature of the upper cycle (tu.li). 2. TCT with slow heating (vk=5–10 K/min) and cooling from tu.li at rates 10–100 K/min makes possible the reduction of austenite grains from No. 4 to No. 11-12.

Thermocyclic treatment of deposited metal in reconditioning support rolls of 9KhF steel

Thermocyclic treatment of deposited metal in reconditioning support rolls of 9KhF steel

Influence of features of the original structure on the phase transformations and properties of steel in heat treatment

1. The original condition of the steel influences not only the kinetics of phase transformations but also the position of the critical points, the degree of recrystallization at a certain temperature in the intercritical temperature range, the composition of the phases formed, and the morphological characteristics of the structures formed. As the result the use of the Fe-C phase diagram for a quantitative description of the process of the α→γ-transformation even at low heating rates is invalid. 2. In the development of hardening cycles from the intercritical temperature range and thermocyclic treatment cycles it is ncessary to take into consideration the actual structure. of the steel, which may have a significant influence on development of the α→γ-transition and on the final properties of the parts.

Thermocyclic treatment of sintered steels — Report 3

Thermocyclic treatment of sintered steels — Report 3

Influence of thermocyclic treatment on the corrosion-mechanical properties of cast 40Kh electroslag steel

Influence of thermocyclic treatment on the corrosion-mechanical properties of cast 40Kh electroslag steel

Thermocyclic treatment of sintered steels ? Report 2

Thermocyclic treatment of sintered steels ? Report 2

Thermocycling treatment of sintered steels ? Report 1

Thermocyclic treatment and subsequent, quenching substantially increase the short-time tensile and transverse rupture strengths, elongation, and impact strength of sintered steels. Furthermore, they markedly improve the quenchability and hardenability of steels with porosities not exceeding 15%.

Effect of thermocyclic treatment on the properties of precipitation-hardening austenitic steel containing lead

1. The mechanical properties of precipitation-hardening austenitic steel 37Kh12N8G8MFB after thermal cycling depend on the amount of the lead impurity. 2. The sharp reduction in the mechanical properties of the steel with a high lead content (0.003%) after TCT is due to the formation and development (due to the Rebinder effect) of intergranular microcracks of the thermal fatigue type. 3. The relationship between the TCT temperature and the susceptibility of the steel with a high lead content and carbide hardening is ambiguous; the susceptibility depends on the thermal stresses that occur during thermal cycling and the decomposition of the super-saturated solid solution.

Thermocyclic treatment of the bimetal steel-wear-resistant iron blanks

1. TCP of blanks made from the bimetal steel-wear-resistant iron does allow one to eliminate the defects of the overheated steel base, i.e., the Widmanstaten structure, and large grain practically without changing the structure of the coating layer whose microhardnes is slightly higher than it was in the initial condition. 2. Use of TCP for the treatment of the bimetal steel-wear-resistant iron permits one to increase the serviceability and life of parts for which these bimetal composites are used.

Probability evaluation of strength under variable loads from median endurance limits of different-size specimens

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Positron annihilation in aluminium, subjected to the thermocyclic treatment

Positron annihilation in aluminium, subjected to the thermocyclic treatment