High Pressure Waterjets – An Innovative Means of Alpha Case Removal for Superplastically Formed Titanium Alloys

2010 ◽  
Vol 433 ◽  
pp. 103-111 ◽  
Author(s):  
A. Chillman ◽  
Mamidala Ramulu ◽  
M. Hashish ◽  
A. Cantrell
Keyword(s):  
High Pressure ◽  
Titanium Alloys ◽  
Material Removal ◽  
Work Piece ◽  
Fine Grain ◽  
Alpha Case ◽  
Material Erosion ◽  
Chemical Milling ◽  
Repetitive Impact ◽  
Cleaning Methods

Ultra high-pressure waterjets (WJ) have gained consideration as a viable alternative to conventional material removal and cleaning methods such as chemical milling, grit blasting, and grinding. Waterjets have often been considered for the stripping of unwanted coatings, but they also exhibit an inherent ability for the controlled milling of metallic materials. The waterjet material removal process poses a secondary benefit – the material erosion occurs due to the repetitive impact of droplets within the waterjet stream, which also serve to induce compressive residual stresses in the shallow sub-surface layers of the work piece. An experimental study was conducted to explore the removal of the alpha case layer on Superplastically Formed conventional and fine grain Ti-6Al-4V specimens. The resulting surface roughness parameters and completeness of alpha layer removal were characterized. Based on the experimental results, waterjet removal processes may serve as an alternate method for the post-processing of Superplastically Formed titanium alloys.

Effects of Cutting Parameters on the Surface Roughness of Ti6Al4V Titanium Alloys in Side Milling

2011 ◽  
Vol 175 ◽  
pp. 289-293 ◽  
Author(s):  
Hao Liu ◽  
Chong Hu Wu ◽  
Rong De Chen
Keyword(s):  
Surface Roughness ◽  
Titanium Alloys ◽  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Cutting Parameters ◽  
Cutting Depth ◽  
Side Milling ◽  
Milling Parameters ◽  
Fine Grain

Side milling Ti6Al4V titanium alloys with fine grain carbide cutters is carried out. The influences of milling parameters on surface roughness are investigated and also discussed with average cutting thickness, material removal rate and vibration. The results reveal that the surface roughness increases with the increase of average cutting thickness and is primarily governed by the radial cutting depth.

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.

scholarly journals Experimental Study of tool Wear Mechanisms in Conventional and High Pressure Coolant Assisted Machining of Titanium Alloy Ti17

2013 ◽  
Vol 554-557 ◽  
pp. 1961-1966 ◽  
Author(s):  
Yessine Ayed ◽  
Guenael Germain ◽  
Amine Ammar ◽  
Benoit Furet
Keyword(s):  
High Pressure ◽  
Titanium Alloy ◽  
Tool Wear ◽  
Titanium Alloys ◽  
Tool Life ◽  
Wear Mechanisms ◽  
Cutting Forces ◽  
Cutting Edge ◽  
Rake Face ◽  
High Pressure Coolant

Titanium alloys are known for their excellent mechanical properties, especially at high temperature. But this specificity of titanium alloys can cause high cutting forces as well as a significant release of heat that may entail a rapid wear of the cutting tool. To cope with these problems, research has been taken in several directions. One of these is the development of assistances for machining. In this study, we investigate the high pressure coolant assisted machining of titanium alloy Ti17. High pressure coolant consists of projecting a jet of water between the rake face of the tool and the chip. The efficiency of the process depends on the choice of the operating parameters of machining and the parameters of the water jet such as its pressure and its diameter. The use of this type of assistance improves chip breaking and increases tool life. Indeed, the machining of titanium alloys is generally accompanied by rapid wear of cutting tools, especially in rough machining. The work done focuses on the wear of uncoated tungsten carbide tools during machining of Ti17. Rough and finish machining in conventional and in high pressure coolant assistance conditions were tested. Different techniques were used in order to explain the mechanisms of wear. These tests are accompanied by measurement of cutting forces, surface roughness and tool wear. The Energy-dispersive X-ray spectroscopy (EDS) analysis technique made it possible to draw the distribution maps of alloying elements on the tool rake face. An area of material deposition on the rake face, characterized by a high concentration of titanium, was noticed. The width of this area and the concentration of titanium decreases in proportion with the increasing pressure of the coolant. The study showed that the wear mechanisms with and without high pressure coolant assistance are different. In fact, in the condition of conventional machining, temperature in the cutting zone becomes very high and, with lack of lubrication, the cutting edge deforms plastically and eventually collapses quickly. By contrast, in high pressure coolant assisted machining, this problem disappears and flank wear (VB) is stabilized at high pressure. The sudden rupture of the cutting edge observed under these conditions is due to the propagation of a notch and to the crater wear that appears at high pressure. Moreover, in rough condition, high pressure assistance made it possible to increase tool life by up to 400%.

Effect of Arc Discharge Pressure on Discharge Current in EDM

2008 ◽  
Vol 381-382 ◽  
pp. 451-454
Author(s):  
Atsutoshi Hirao ◽  
S. Tai ◽  
H. Takezawa ◽  
Naotake Mohri ◽  
Kazuro Kageyama ◽  
...  
Keyword(s):  
Discharge Current ◽  
Electrical Discharge ◽  
Material Removal ◽  
Electrical Discharge Machining ◽  
Arc Discharge ◽  
Vibration Sensor ◽  
Work Piece ◽  
Tool Electrode ◽  
Discharge Pressure ◽  
Current Behavior

In electrical discharge machining (EDM), an electrical discharge occurs between a tool electrode and a work-piece, and removal of materials is carried out by vaporized explosion between the electrode and the work-piece. However, the mechanism of material removal in EDM is not well understood. In order to clarify this issue, the acoustic emission (AE) method has been applied to examine the force of explosion, and the Schlieren visualization method has been applied to observe the explosion. In this study, we investigate the effect of discharge current behavior on the occurrence of the AE waves by means of an optical fiber vibration sensor.

Effect of High Pressure Torsion on Crystal Orientation to Improve the Thermoelectric Property of a Bi2Te3-Based Thermoelectric Semiconductor

2010 ◽  
Vol 89-91 ◽  
pp. 41-46 ◽  
Author(s):  
Maki Ashida ◽  
Takashi Hamachiyo ◽  
Kazuhiro Hasezaki ◽  
Hirotaka Matsunoshita ◽  
Z. Horita
Keyword(s):  
High Pressure ◽  
Power Factor ◽  
Crystal Orientation ◽  
High Pressure Torsion ◽  
Preferred Orientation ◽  
Orientation Factor ◽  
X Ray Diffraction ◽  
Fine Grain ◽  
Maximum Value ◽  
P Type

A Bi2Te3-based thermoelectric semiconductor was subjected by high pressure torsion (HPT). Sample disks of p-type Bi0.5Sb1.5Te3.0 were cut from sintered compacts that were made by mechanically alloying (MA) followed by hot pressing. Disks were subjected by HPT with 1, 5 and 10 turns at 473 K under 6.0 GPa of pressure. Crystal orientation was investigated by X-ray diffraction. Microstructures were characterized using scanning electron microscopy. Results indicated that HPT disks after 5 turns had a preferred orientation and a fine grain compared with pre-HPT disks while the orientation factor was decreased after HPT using 10 turns. The power factor had a maximum value at 5 turns as determined by measuring its thermoelectric properties. A maximum power factor of 4.30×10-3 Wm-1K-2 was obtained for HPT disks after 5 turns. This value was larger than that for the pre-HPT disk. The over-HPT of 10 turns was found to have caused a decrease in the preferred orientation leading to a low power factor.

Modeling of Material Removal Mechanism in Micro Electric Discharge Milling of Ti-6Al-4V

2014 ◽  
Vol 592-594 ◽  
pp. 516-520 ◽  
Author(s):  
Basil Kuriachen ◽  
Jose Mathew
Keyword(s):  
Material Removal Rate ◽  
Feed Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Milling Process ◽  
Work Piece ◽  
Machining Parameters ◽  
Removal Mechanism ◽  
Material Removal Mechanism ◽  
Electric Discharge Milling

Micro EDM milling process is accruing a lot of importance in micro fabrication of difficult to machine materials. Any complex shape can be generated with the help of the controlled cylindrical tool in the pre determined path. Due to the complex material removal mechanism on the tool and the work piece, a detailed parametric study is required. In this study, the influence of various process parameters on material removal mechanism is investigated. Experiments were planned as per Response Surface Methodology (RSM) – Box Behnken design and performed under different cutting conditions of gap voltage, capacitance, electrode rotation speed and feed rate. Analysis of variance (ANOVA) was employed to identify the level of importance of machining parameters on the material removal rate. Maximum material removal rate was obtained at Voltage (115V), Capacitance (0.4μF), Electrode rotational Speed (1000rpm), and Feed rate (18mm/min). In addition, a mathematical model is created to predict the material removal

Solution to Technological Problems of Raising the Reliability and Quality of Castings Based on Titanium Alloys

2019 ◽  
Vol 946 ◽  
pp. 258-264
Author(s):  
Galina I. Shcherbakova ◽  
Maxim S. Varfolomeev ◽  
Pavel A. Storozhenko
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Contact Interaction ◽  
Physicochemical Interaction ◽  
Alpha Case ◽  
Aluminum Yttrium ◽  
Temperature Melting ◽  
Cast Products

We consider the problems of the complex application of the aluminium-yttrium binder in the fabrication of high-temperature resistant melting crucibles and investment molds thermoschemically resistant to titanium melts. The results of the contact interaction investigations of a molten titanium alloy with a material of aluminum-yttrium ceramics are presented. The usage of ceramic products of α-Al2O3–Y3Al5O12∙α-Al2O3 composition under conditions of high-temperature melting and pouring under vacuum minimizes the physicochemical interaction and significantly reduces the alpha case layer on cast products, thereby improving their operational properties.

Thermodynamic Calculation of Alpha-Case Formation in Titanium Alloys

2007 ◽  
pp. 519-522
Author(s):  
Si Young Sung ◽  
Bong Jae Choi ◽  
Sang Ho Noh ◽  
Chang Su Hahn ◽  
Yong Mun Ryu ◽  
...  
Keyword(s):  
Titanium Alloys ◽  
Thermodynamic Calculation ◽  
Alpha Case

Studying the Temperature Effect During the High-Pressure Phase Transformation of Silicon via Indentations

2012 ◽  
Author(s):  
Deepak Ravindra ◽  
John Patten ◽  
Muralidhar K. Ghantasala
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Temperature Effect ◽  
Brittle Material ◽  
Material Removal ◽  
Thermal Softening ◽  
High Pressure Phase ◽  
Ductile Mode ◽  
Indentation Tests ◽  
Pressure Phase

Micro-laser assisted machining (μ-LAM) is a novel micro/nano machining technique developed for ductile mode machining of ceramics and semiconductors. Ductile mode material removal is possible in a nominally brittle material due to the high-pressure phase transformation (HPPT) phenomenon during the machining process. This study isolates the pressure and temperature effect in the μ-LAM process. The μ-LAM process is unique whereby the pressure and temperature effect occur concurrently leading to the material removal process. The effect of temperature and thermal softening is studied via indentation tests using a cutting tool. In the precisely controlled indentation tests, laser heating is applied at various stages to determine the phase (i.e. atmospheric Si-I phase or high pressure phases that benefits most from the thermal softening effect. The indentation depths are measured and compared for each condition to identify the enhanced ductility of the nominally brittle material caused by the laser irradiation.

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