Development and Removal of Alpha-Case Layer From Heat Treated Titanium Alloys

2017 ◽  
Author(s):  
Nikita Mohite ◽  
Sachin Biradar ◽  
Jyoti Shankar Jha ◽  
Sushil Mishra ◽  
Asim Tewari
Keyword(s):  
Oxide Layer ◽  
Elevated Temperatures ◽  
Fatigue Crack Initiation ◽  
Fixed Time ◽  
Hardness Profile ◽  
Air Cooling ◽  
Initiation Zone ◽  
Alpha Case ◽  
Heat Treated ◽  
Aero Engines

The components of the aero engines such as fan blades are generally manufactured from Titanium alloy forgings. At the elevated temperatures, the affinity of Titanium towards oxygen is very high, which results in formation of oxide layer on surface known as alpha-case layer. This alpha-case is both hard and brittle in nature which results in localized micro failure during its application. This gives rise to a fatigue crack initiation zone and compromises the integrity of the component, causing it to fail. To investigate this, Titanium α-β (Ti 64), α (Sn) and β (Mo) alloys were heat treated at 1010°C for 30min, 60min, 90min and 120min followed by air cooling. Formation of alpha-case layer in Ti-6Al-4V, Ti-Sn and Ti-Mo increased from 120.5μm to 391.1μm, 128.77μm to 443.23μm, 105.75μm to 262.46μm at 30mins and 120mins respectively. Chemical treatment, cathodic de-oxygenation, surface coating and laser ablation methods are generally used to remove the alpha case. In the current study, acid pickling is used to remove the alpha case layer, as this process is simple and also easily applicable to any complex shape of the material. In this method, samples were dipped in the solution of HF (5%) and HNO3 (35%) at 80 °C for fixed time at fixed intervals to find the rate of alpha case removal. Micro indentation was carried out to obtain hardness profile from surface to bulk of heat treated specimen. The quantification of alpha case oxide layer from surface to bulk was done by EDS.

An Air-Cooled Jacket Designed to Protect Unsteady Pressure Transducers at Elevated Temperatures in Gas Turbine Engines

2002 ◽  
Author(s):  
Paul C. Ivey ◽  
Derek G. Ferguson
Keyword(s):  
Gas Turbine ◽  
Pressure Transducer ◽  
Elevated Temperatures ◽  
Thermal Protection ◽  
Pressure Sensors ◽  
Air Cooling ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Cooling Media ◽  
Aero Engines

Current unsteady pressure sensors have a limiting upper temperature range and with few exceptions cannot survive at the temperatures experienced in gas turbine aero-engines. This paper describes a design and development study of an air-cooled commercially available unsteady pressure transducer capable of operation at temperatures exceeding 900 °C. The research objective for this work is the following: To design a cooling adapter, using air as the cooling media, capable of protecting a standard unsteady pressure transducer, whose maximum operating temperature is around 250 °C. in a gas turbine engine environment where temperatures typically reach 800–l500 °C. In addition the provision of thermal protection must not adversely effect the measurement of unsteady pressure and the cooling adapter and transducer assembly must be small enough to access critical parts of the engine. Current transducer can operate at temperatures exceeding 250 °C; the purpose of this paper is to demonstrate the additional protection offered by air-cooling. The paper describes the validation experiments conducted for this design, the level of thermal protection achieved and the frequency response of the transducer/cooling jacket assembly.

Alpha Case Characterization of Hot Rolled Titanium

2014 ◽  
Vol 1019 ◽  
pp. 311-317 ◽  
Author(s):  
Francois Conradie ◽  
Nico Treurnicht ◽  
Natasha Sacks
Keyword(s):  
Titanium Alloys ◽  
Oxide Layer ◽  
Fatigue Crack Initiation ◽  
Weight Ratio ◽  
Inert Gas ◽  
Atmospheric Conditions ◽  
Capital Costs ◽  
Alpha Case ◽  
Gas Atmosphere ◽  
Chemical Milling

Titanium alloys offer excellent corrosion resistance, good strength to weight ratio, is nonmagnetic and biocompatible. This allows them to be used in demanding applications and specialised industries ranging from aviation to medicine. However, at high temperatures the metal is chemically reactive which requires several manufacturing processes such as melting and welding to be performed either in vacuum or inert gas atmosphere. Some processes such as rolling are impractical to be performed in inert gas atmosphere. Titanium alloys, notably Ti-6Al-4V, develops a hard oxide layer on the outer surface during hot processing, such as rolling, in atmospheric conditions. This oxide layer, commonly referred to as the alpha case, is both hard and brittle. The increased Young's modulus of the alpha case creating an outer layer with increased stiffness where maximum stresses occur, results in localized micro failure. The micro failures in this layer serve as a fatigue crack initiation zone, compromising the integrity of the component and causing it to fail. Traditionally alpha case is removed by means of chemical milling in hot acid baths using aggressive acids such as Hydrofluoric acid. The facilities needed for chemical milling require high capital costs as well as stringent and costly safety requirements. Lastly, the disposal of used acids is proving to become increasingly difficult due to the strict South African environmental laws. Removal of this layer by means of light pass machining has therefore become more desirable, however at present it remains economically infeasible. This study presents an overview of the materials background, alpha case formation and related machining considerations. Experiments that investigate alpha case properties are included.

Crystallographic Differences of Metastable NI2MO in a NI-MO-AL Superalloy

1980 ◽  
Vol 38 ◽  
pp. 158-159
Author(s):  
Michael M. Kersker ◽  
E. A. Aigeltinger ◽  
J. J. IIren
Keyword(s):  
Mechanical Properties ◽  
Air Cooling ◽  
Solution Treated ◽  
Heat Treated ◽  
Metastable Compounds ◽  
Rapidly Solidified

Ni-rich alloys based on approximate ternary composition Ni-8Mo-15A1 (at%) are presently under investigation in an attempt to study the contribution, if any, of the profusion of Mo-rich NixMo metastable compounds that these alloys contain to their excellent mechanical properties. One of the alloys containing metastable NixMo precipitates is RSR 197 of composition Ni-8.96Mo-15.06A1-1.98Ta-.015Yt. The alloy was prepared at Pratt and Whitney Government Products Division, West Palm Beach, Florida, from rapidly solidified powder. The powder was canned under inert conditions and extruded as rod at 1315°C. The as-extruded rod, after air cooling, was solution treated at 1315°C for two hours, air cooled, and heat treated for one hour at 815°C, followed again by air cooling.

FEDERATED F401.5Ni

Alloy Digest ◽  
1974 ◽  
Vol 23 (12) ◽  
Keyword(s):  
Fracture Toughness ◽  
Elevated Temperatures ◽  
High Strength ◽  
Heat Treating ◽  
Casting Alloy ◽  
Aluminum Casting ◽  
Aluminum Casting Alloy ◽  
Treated Condition ◽  
Heat Treated ◽  
Heat Treated Condition

Abstract FEDERATED F401.5Ni is a heat-treatable aluminum casting alloy with high strength and good wear resistance in the fully heat-treated condition. It is recommended for castings requiring good strength at elevated temperatures. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: Al-212. Producer or source: Federated Metals Corporation, ASARCO Inc..

scholarly journals Effect of Heat Treatment on the As-Cast Microstructure and Hardness of NiSi3B2 Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 539
Author(s):  
Gonçalo M. Gorito ◽  
Aida B. Moreira ◽  
Pedro Lacerda ◽  
Manuel F. Vieira ◽  
Laura M. M. Ribeiro
Keyword(s):  
Heat Treatment ◽  
Elevated Temperatures ◽  
Casting Process ◽  
X Ray Diffraction ◽  
Heat Treated ◽  
Energy Dispersive Microanalysis ◽  
Eutectic Constituent ◽  
Backscattered Electron ◽  
Corrosion And Oxidation ◽  
Cast Microstructure

Cast Ni-Si-B alloys have the potential for high-temperature applications because of their high resistance to wear, impact, corrosion, and oxidation at elevated temperatures due to an appropriate balance of hard phases and austenite that ensures a good compromise between toughness and hardness. In this work, NiSi3B2 specimens, fabricated by the lost-wax casting process, were investigated. Given the complex multiphase cast microstructure, a differential scanning calorimeter (DSC-TGA) analysis was employed to characterize the reactions that occur during solidification and the resulting phases were characterized using scanning electron microscopy (SEM), with energy-dispersive microanalysis (EDS) and backscattered electron (BSE) image and X-ray diffraction (XRD). Due to the presence of hard phases, machining of the Ni-Si-B components can pose additional difficulties. Therefore, the conditions of the solution heat treatment, which might lead to the homogenization of the microstructure, consequently improving its machinability, were also investigated. The results of the heat-treated samples indicated that the dissolution of the eutectic constituent is accompanied by a significant decrease in the hardness (approximately 17%). It is important to emphasize that the solution heat treatments carried out reduced the hardness without affecting the percentage of borides, which will allow improving the machinability without adversely affecting the alloy performance in service.

Creep Tests of Rotating Disks at Elevated Temperature and Comparison With Theory

1954 ◽  
Vol 21 (3) ◽  
pp. 225-235
Author(s):  
A. M. Wahl ◽  
G. O. Sankey ◽  
M. J. Manjoine ◽  
E. Shoemaker
Keyword(s):  
Elevated Temperatures ◽  
Experimental Program ◽  
Test Results ◽  
Rotating Disks ◽  
Creep Tests ◽  
Shear Theory ◽  
Heat Treated ◽  
Long Time ◽  
Average Tension ◽  
Creep Deformations

Abstract A theoretical and experimental program involving methods of calculating creep in rotating disks at elevated temperatures is described. This program consisted primarily of the following: (a) Obtaining forged disks from the same ingot of 12 per cent chrome steel, all disks being forged and heat-treated in the same manner; (b) making spin tests at 1000 F on three of these disks for periods up to about 1000 hr; ( ) making long-time tension-creep tests at 1000 F on many specimens cut out circumferentially from several of the other disks at stresses approximating those of the spin tests; (d) investigating theoretical methods of calculation of creep deformation in such disks; and (e) comparison of spin-test results with those calculated theoretically using average tension-creep data. It was found that available methods of calculating rotating disks based on the Mises criterion gave creep deformations too low compared to the test values, i.e., on the unsafe side for design. Considerably better agreement between test and theoretical results is obtained if the latter is based on the maximum-shear theory. Some discussion is given of the reasons for the better agreement obtained using the latter theory; these are believed to be related in part to the anisotropy of the forged material tested. Further tests on other materials are necessary before general conclusions can be drawn; however, in the absence of test data it is suggested that a conservative course in design for such disks is to apply the maximum-shear theory.

Effect of Annealing on the Structure of Buried SiO2 Layers Formed By Elevated Temperature High Dose Oxygen Implantation

1985 ◽  
Vol 53 ◽  
Author(s):  
S.J. Krause ◽  
C.O. Jung ◽  
S.R. Wilson ◽  
R.P. Lorigan ◽  
M.E. Burnham
Keyword(s):  
Single Crystal ◽  
Oxide Layer ◽  
Elevated Temperatures ◽  
Superficial Layer ◽  
Silicon On Insulator ◽  
High Dose ◽  
Threading Dislocations ◽  
Heater Temperature ◽  
Buried Oxide ◽  
Structural Differences

ABSTRACTOxygen has been implanted into Si wafers at high doses and elevated temperatures to form a buried SiO2 layer for use in silicon-on-insulator (SOI) structures. Substrate heater temperatures have been varied (300, 400, 450 and 500°C) to determine the effect on the structure of the superficial Si layer through a processing cycle of implantation, annealing, and epitaxial growth. Transmission electron microscopy was used to characterize the structure of the superficial layer. The structure of the samples was examined after implantation, after annealing at 1150°C for 3 hours, and after growth of the epitaxial Si layer. There was a marked effect on the structure of the superficial Si layer due to varying substrate heater temperature during implantation. The single crystal structure of the superficial Si layer was preserved at all implantation temperatures from 300 to 500°C. At the highest heater temperature the superficial Si layer contained larger precipitates and fewer defects than did wafers implanted at lower temperatures. Annealing of the as-implanted wafers significantly reduced structural differences. All wafers had a region of large, amorphous 10 to 50 nm precipitates in the lower two-thirds of the superficial Si layer while in the upper third of the layer there were a few threading dislocations. In wafers implanted at lower temperatures the buried oxide grew at the top surface only. During epitaxial Si growth the buried oxide layer thinned and the precipitate region above and below the oxide layer thickened for all wafers. There were no significant structural differences of the epitaxial Si layer for wafers with different implantation temperatures. The epitaxial layer was high quality single crystal Si and contained a few threading dislocations. Overall, structural differences in the epitaxial Si layer due to differences in implantation temperature were minimal.

Embrittlement Behavior of Isothermally Heat-Treated T/P92 Steel at 350°C

2007 ◽  
Vol 345-346 ◽  
pp. 465-468 ◽  
Author(s):  
Ja Min Koo ◽  
Sung Yong Kim ◽  
Kee Sam Shin ◽  
Yeon Gil Jung ◽  
Sung Kang Hur
Keyword(s):  
Power Plants ◽  
Structural Integrity ◽  
Air Cooling ◽  
Boiler Tube ◽  
P92 Steel ◽  
Heat Treated

P92 steels as well as P91 are widely used as boiler tube materials of ultra super critical (USC) power plants these days. And thus embrittlement is very important for structural integrity of the USC plants. The embrittlement was observed when P92 (Modified 9Cr-1.8W-0.5Mo-V-Nb) steels were quenched to and held at the temperature of 320 to 350°C, which were the temperatures intermediate between Ms and Mf, and then air-cooled. Nearly same kind of the embrittlement had been observed with the T/P91 steels and a theory had been proposed to explain the mechanism of the embrittlement by us. From the theory, the embrittlement might be caused by the brittle martensite which is freshly formed during air-cooling. We tried to apply the theory for the embrittlement of the T/P92 steel. The behaviors of the embrittled T/P92 steel were explained well by the theory.

Effect of Melt Treatment on the Microstructure and Creep-Rupture Behavior of M963 Cast Nickel-Base Superalloy

2004 ◽  
Vol 449-452 ◽  
pp. 553-556
Author(s):  
Heng Rong Guan ◽  
Feng Shi Yin ◽  
Xiao Feng Sun ◽  
Zhuang Qi Hu
Keyword(s):  
Creep Rupture ◽  
Striking Difference ◽  
Nickel Base Superalloy ◽  
Air Cooling ◽  
Melt Treatment ◽  
Heat Treated ◽  
Treatment Changes ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Rupture Behavior

The effect of melt treatment on the microstructure and creep-rupture behavior of M963 superalloy at 1248K under 225MPa has been investigated. The microstructure of the as-cast superalloy without melt treatment consists of γ solid solution matrix, γ´precipitate, coarse blocky MC carbide and (γ+γ´)eutectic. The striking difference in microstructure is that the melt treatment changes the MC carbide from the coarse blocky morphology into the fine script-like morphology. After heat-treated at 1483K for 4h followed by air-cooling, both the creep life and rupture elongation of the melt-treated alloy are all doubled those of the alloy without melt treatment. The mechanism of the melt treatment on the creep-rupture behavior of the M963 superalloy is discussed.

Residual Stress Analysis Considering Phase Transformation and Transformation Plasticity for Heat-Treated Large Size Shaft

2016 ◽  
Vol 725 ◽  
pp. 647-652 ◽  
Author(s):  
Yusuke Yanagisawa ◽  
Yasuhiro Kishi ◽  
Katsuhiko Sasaki
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Phase Transformation ◽  
Air Cooling ◽  
Water Cooling ◽  
Stress Distributions ◽  
Transformation Plasticity ◽  
Large Size ◽  
Heat Treated ◽  
Good Agreement

The residual stress distributions of the forgings after both water-cooling and air-cooling were measured experimentally. The residual stress occurring during the heat-treatment was also simulated considering the phase transformation and the transformation plasticity. A comparison of the experiments with the simulations showed a good agreement. These results shows that the transformation plastic strain plays an important role in the heat treatment of large forged shafts.

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