scholarly journals The formation of structure regularities in the recrystallized near-surface layer after restoration by heat treatment process of nickel-based high-temperature strength alloys

2021 ◽  
Vol 97 (1) ◽  
pp. 53-65
Author(s):  
К.А. Yushchenko ◽  
◽  
O.V. Yarovytsyn ◽  
T.M. Kushnaryova ◽  
V.E. Mazurak ◽  
...  
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Grain Boundaries ◽  
Turbine Blades ◽  
Turbine Engines ◽  
High Temperature Strength ◽  
Vacuum Heat Treatment ◽  
Isothermal Exposure ◽  
Near Surface ◽  
A Chain

In modern nickel nickel-based high-temperature strength alloys of the ZhS32 type with a directional and single-crystal structure on surfaces that were previously subjected to mechanical treatment, with the subsequent isothermal exposure in the vicinity of the homogenization temperature lasting more than 15 minutes a subsurface recrystallized layer up to 40-65 μm deep is formed such us a chain of grains. The formation of this layer is a side effect that restrained the industrial application of vacuum heat treatment to restore local operational degradation ("raft"-structure) on the overheated inlet edges of non-bandage shelved gas-cooled high-pressure turbine blades of some modern aircraft turbine engines. Given the technical complexity of reliable removal of this recrystallized layer from the tract surface of thin-walled gas-cooled blades, it is important to develop technological measures to translate grain boundaries in unremoved residues of recrystallized near-surface layer into a safer structural state. The regularities of recrystallized layer formation in the process of 3-stage reductive vacuum treatment has been investigated by the methods of raster electron microscopy and X-ray structural (EDX) microanalysis at magnification up to × 2000 on fragments of TVT blades with ZhS26-VI alloy (directional structure) and ZhS32-VI alloy (monocrystalline structure). It has been established that the recrystallized layer formed in the process of aging 1.25-1.5 hours at the temperature of alloy homogenization, is a chain of grain with a tightly packed γ׳-phase with layers at their boundaries, which consist of the non-reinforcing γ׳-phase up to 1-3 μm wide with the carbide phases presence. It has been shown that the rational choice of the temperature of high-temperature aging is an effective technological control of the grain boundaries structural state in a near-surface recrystallized layer of the considered high-temperature strength alloys. Assigning a temperature of 1050°C for isothermal exposure after homogenization heat treatment for ZhS26 and ZhS32 alloys allows to reduce the grain boundaries width in the recrystallized layer to 1-2 μm, keep them intermittent and avoid systematic release of carbide particles at the grain boundaries. On the basis of established in the Paton welding institute of regularities of formation and control of the structure of the near-surface recrystallized layer developed technological recommendations for optimizing the vacuum heat treatment modes to restore the structure of non-bandage shelved gas-cooled high-pressure turbine blades with type ZhS32 high-temperature strength alloys. This technology has passed experimental and practical testing during the next maintenance cycle of flight operation on one of the modern turbojet double-circuit gas turbine engines with afterburner combustion chamber. Keywords: nickel nickel-based high-temperature strength alloys, vacuum heat treatment, restoration of alloys structure, subsurface recrystallized layer, raster electron microscopy.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

Heat Resistance of Ferritic Stainless Steels with 15% Chromium for Automobile Exhaust System

2011 ◽  
Vol 239-242 ◽  
pp. 1799-1803
Author(s):  
Hua Bing Li ◽  
Zhou Hua Jiang ◽  
Qi Feng Ma ◽  
Dong Ping Zhan
Keyword(s):  
High Temperature ◽  
Grain Boundaries ◽  
Thermal Fatigue ◽  
Fatigue Cracks ◽  
Exhaust System ◽  
High Temperature Strength ◽  
Temperature Oxidation ◽  
Ferritic Stainless Steels ◽  
Automobile Exhaust ◽  
Thermal Fatigue Cracks

The high-temperature strength and thermal fatigue properties of Fe-Cr-Nb-Mo ferritic stainless steel (FSSNEW) developed for automobile exhaust system were investigated. The results show that the high-temperature tensile strength and yield strength of FSSNEW are better than or equal to those of the presently applied ferritic stainless steels. The thermal fatigue cracks nucleate at the V-notch. The inclusions along grain boundaries become prior regions for initiation of the cracks. The inclusions distributed at the defects make the formation of cracks in the materials easily through the effects of cycle thermal stress and thermal strain. The length and propagated rate of thermal fatigue cracks increase with the maximum tested temperature increasing. When the maximum temperature arrives at 900°C, the high-temperature oxidation is serious along the grain boundaries, which aggravates the cracks propagating along the grain boundaries. The principle mechanism of stress assisted grain boundary oxygen (SAGBO) embrittlement can be applied to illustrate the effects of external stress on aggravating the damage caused by environmental factors. Therefore, the high-temperature oxidation is the main reason for the propagation of thermal fatigue cracks. The FSSNEW is satisfied for the applied requirement of high-temperature strength in the hot side of the automobile exhaust system.

Characterization of Electrolytically Deposited CdSe on Ti Substrates

2010 ◽  
Vol 297-301 ◽  
pp. 912-917 ◽  
Author(s):  
T.G. Argyropoulos ◽  
Jelica Novakovic ◽  
M.D. Athanassopoulou ◽  
P. Vassiliou ◽  
J.A. Mergos ◽  
...  
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Surface Morphology ◽  
Bath Temperature ◽  
Vacuum Heat Treatment ◽  
Bath Solution ◽  
Zinc Blende ◽  
Zinc Blende Structure

Electrolytical deposition of CdSe on Ti substrates from CdSO4 - SeO2 solutions is investigated. The effect of the bath temperature was investigated and how it affects the CdSe deposits. According to the XRD spectra, the obtained CdSe films exhibit the cubic zinc-blende structure that remains unaffected by vacuum heat treatment (650°C). The surface morphology of the films differs significantly with bath solution temperatures. When Au contacts are used, the Ti/CdSe/Au structure may exhibit rectifying properties depending on the temperature during the electrodeposition. High temperature baths make the deposits to obtain ohmic properties.

scholarly journals Effect of Heat Treatment on High-Temperature Strength of A286 Alloy

1963 ◽  
Vol 49 (2) ◽  
pp. 160-165 ◽  
Author(s):  
Taro HASEGAWA ◽  
Fukunaga TERASAKI
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
High Temperature Strength

Turbine Blade Distortion after Heat Treatment: Preliminary Experimental Investigation and FEM Analysis

2019 ◽  
Vol 827 ◽  
pp. 98-103
Author(s):  
F. de Bona ◽  
Alex Lanzutti ◽  
G. Lucacci ◽  
Luciano Moro ◽  
Jelena Srnec Novak
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Material Properties ◽  
Turbine Blades ◽  
Laser Scanner ◽  
Fem Analysis ◽  
Element Model ◽  
Diffusional Creep ◽  
High Temperature Treatment ◽  
Temperature Phase

During the production process, turbine blades are subjected to a solubilization heat treatment, followed by tempering treatment, in order to obtain better mechanical properties. It is observed that, in some cases, permanent distortion can occur during the high temperature treatment (austenitising temperature). In this work, a high temperature creep resisting steel blade with a simplified geometry is considered. A finite element model is developed considering: the material properties depending on temperature, phase transformation and viscoplasticity (Nabarro-Herring and bilinear kinematic models). A nonlinear transient thermo-mechanical analysis is performed to simulate a standard thermal cycle. Material properties are partially calibrated based on dilatometric tests and partially from data available in literature. Adopting a laser scanner system, the blades geometry is measured before and after the heat treatment to calculate the permanent deflection. Comparing numerical results with experiments, it has been observed that the distortion phenomenon is mainly affected by the low-stress diffusional creep. This effect is due to the fact that, during the heat treatment, the blade is held at high temperature for a relatively long time according to a particular supporting lay-out. To minimize the permanent distortion, the numerical model permits an appropriate supporting system to be set-up, whose validity has been confirmed experimentally.

METGLAS MBF-75/75A

Alloy Digest ◽  
1983 ◽  
Vol 32 (5) ◽  
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Metallic Glass ◽  
Physical Properties ◽  
Stainless Steels ◽  
Solidus Temperature ◽  
High Temperature Strength ◽  
High Temperature Alloys

Abstract METGLAS MBF-75A is a brazing foil in ductile, flexible metallic-glass form (a similar grade, MBF-75, is identical except that it has larger dimensional tolerances). It has excellent high-temperature strength and flows readily into narrow joints. Its high solidus temperature facilitates heat treatment of some superalloys without remelting the joint. It is recommended for joining high-temperature alloys and stainless steels. This datasheet provides information on composition, physical properties, microstructure, and hardness. It also includes information on joining. Filing Code: Ni-286. Producer or source: Allied Corporation.

Effect of Cr content and heat-treatment on the high temperature strength of eutectic Al–Si alloys

2015 ◽  
Vol 647 ◽  
pp. 63-69 ◽  
Author(s):  
Yuying Yang ◽  
Sheng-Yi Zhong ◽  
Zhe Chen ◽  
Mingliang Wang ◽  
Naiheng Ma ◽  
...  
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
High Temperature Strength ◽  
Cr Content
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