Surface Hardening of Ceramic Oxide and Metal Alloy Single Crystals by Ultrasonic Cavitation

1993 ◽  
Vol 318 ◽  
Author(s):  
James R. Brewster ◽  
Y. Powell-Friend ◽  
L. A. Boatner
Keyword(s):  
Stainless Steel ◽  
Single Crystal ◽  
Single Crystals ◽  
Ultrasonic Treatment ◽  
Surface Hardening ◽  
Surface Hardness ◽  
Ultrasonic Cavitation ◽  
Indentation Hardness ◽  
Damage And Failure ◽  
Micro Indentation

ABSTRACTCavitation effects have long been considered to be undesirable phenomena that resulted in the damage and failure of metallic components. In the present work, we establish that, in fact, controlled applications of ultrasonic cavitation phenomena can be used to enhance the surface properties of both ceramics and metals. Polished (100) surfaces of single-crystal MgO and single crystals of 70%Fe-15%Ni-15%Cr (stainless-steel) were subjected to ultrasonically induced cavitation by exposure to 20 kHz excitations (at ∼ 100 W/cm2) in isopropanol. Knoop micro-indentation hardness measurements on untreated and ultrasonically treated areas of the surfaces revealed a hardening that increased with the duration of the ultrasonic treatment up to a saturation level. Relative increases in the surface hardness of up to 30% in the case of MgO and ∼250% in the case of Fe-Ni-Cr were obtained. It was found that the rate of hardening was not uniform over the surface but was more rapid on those portions of the surface that were directly under the edge of the ultrasonically vibrating horn tip.

Hardness-Damage Correlations in Ta Implanted Single Crystal Ni3Al

1989 ◽  
Vol 157 ◽  
Author(s):  
Gary S. Was ◽  
Siegfried Mantl ◽  
Warren Oliver
Keyword(s):  
Single Crystal ◽  
Surface Hardening ◽  
Room Temperature ◽  
Effective Means ◽  
Surface Hardness ◽  
Lattice Location ◽  
Depth Profiles ◽  
Low Load ◽  
Subsequent Diffusion ◽  
Load Indentation

ABSTRACTImplantation of Ta into single crystal Ni3Al was conducted to determine whether this would be an effective means of producing surface hardening in monolithic alloys. Ta was implanted at 400 keV to doses of 0.7, 3.6 and 25.2 × 1015 cm2 along the <100> axis of a <100> crystal of Ni3A1 at room temperature. Composition vs depth profiles were determined by RBS and lattice location of Ta was determined by channeling angular yield scans about the <100> axis. The hardness of the surface was measured by ultra-low load indentation. Results show that implantation softens the surface and that the Ta is randomly distributed between Ni and A1 sites. Annealing at 1000°C/1h significantly reduces the damage and causes preferential occupation of A1 sites by Ta. It also results in a slight increase in surface hardness. Further annealing at 1200°C/0.25 h increases the surface hardness substantially. The results indicate that the as-implanted surface is softened by disordering and subsequent diffusion of Ta to A1 sites causes hardening of the surface.

Ultrasonic Cavitation Peening of Stainless Steel and Nickel Alloy

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Yibo Gao ◽  
Benxin Wu ◽  
Ze Liu ◽  
Yun Zhou ◽  
Ninggang Shen ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Nickel Alloy ◽  
Vibration Amplitude ◽  
Surface Hardness ◽  
Surface Profile ◽  
Ultrasonic Cavitation ◽  
Surface Microhardness ◽  
Workpiece Surface ◽  
Different Depths

Ultrasonic cavitation peening is a peening process utilizing the high pressure induced by ultrasonic cavitation in liquids (typically water). In this paper, ultrasonic cavitation peening on stainless steel and nickel alloy has been studied. The workpiece surface microhardness, the microhardness variation at different depths, the workpiece surface profile, roughness, and morphology have been measured or observed. It has been found that for the studied situations, ultrasonic cavitation peening (at a sufficiently high horn vibration amplitude) can obviously enhance the workpiece surface hardness without significantly increasing the surface roughness. Under the investigated conditions, a surface layer of more than around 50 μm has been hardened under a horn vibration amplitude of ∼20 μm.

Ultrasonic Cavitation Peening of Stainless Steel and Nickel Alloy

2013 ◽  
Author(s):  
Yibo Gao ◽  
Benxin Wu ◽  
Ze Liu ◽  
Yun Zhou
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Nickel Alloy ◽  
Vibration Amplitude ◽  
Surface Hardness ◽  
Ultrasonic Cavitation ◽  
Workpiece Surface ◽  
Oxygen Contamination ◽  
Scanning Electron

Ultrasonic cavitation peening is a peening process utilizing the high pressure induced by ultrasonic cavitation in liquids (typically water). However, the relevant previous investigations in the literature have been limited. In this paper, ultrasonic cavitation peening on stainless steel and nickel alloy has been studied, including the observation or characterization of the surface hardness, morphology, profile, roughness and oxygen contamination of treated workpiece samples. It has been found that for the studied situations, ultrasonic cavitation peening (at a sufficiently high horn vibration amplitude) can obviously enhance the workpiece surface hardness without significantly increasing the surface roughness, changing surface morphology observed by scanning electron microscope (SEM), or contaminating the surface by oxygen.

Lattice location and hardness of Ta-implanted Ni3Al

1991 ◽  
Vol 6 (6) ◽  
pp. 1200-1206 ◽  
Author(s):  
Gary S. Was ◽  
Siegfried Mantl ◽  
Warren Oliver
Keyword(s):  
Thermal Treatment ◽  
Single Crystal ◽  
Surface Hardening ◽  
Room Temperature ◽  
Surface Hardness ◽  
Lattice Location ◽  
Depth Profiles ◽  
Low Load ◽  
Subsequent Diffusion ◽  
Load Indentation

Implantation of Ta into single crystal Ni3Al was conducted to determine the degree of surface hardening in monolithic alloys in relation to its lattice location. Ta was implanted at 400 keV to doses of 0.07, 0.36, and 2.52 × 1016 cm−2 along the [100] axis of a [100] crystal of Ni3Al at room temperature. Composition versus depth profiles were determined by RBS, and lattice location of Ta was determined by channeling angular yield scans about the [100] axis. The hardness of the surface was measured by ultra-low load indentation. Results show that implantation softens the surface and that the Ta is randomly distributed between Ni and Al sites. Annealing at 1000 °C/1 h significantly reduces the damage and causes preferential occupation of Al sites by Ta, resulting in a slight increase in surface hardness. Further annealing at 1200 °C/0.25 h increases the surface hardness substantially and increases occupation of Al lattice sites to roughly 84%. Results are consistent with a model in which the as-implanted surface is softened by disordering, and subsequent diffusion of Ta to Al sites during thermal treatment causes hardening of the surface.

Syntheses and Crystal Structures of Sr7H12X2 (X = Cl, Br)

2008 ◽  
Vol 63 (5) ◽  
pp. 513-518 ◽  
Author(s):  
Olaf Reckeweg ◽  
Jay C. Molstad ◽  
Scott Levy ◽  
Constantin Hoch ◽  
Francis J. DiSalvo
Keyword(s):  
Stainless Steel ◽  
Single Crystal ◽  
Single Crystals ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
The Difference ◽  
Difference Fourier ◽  
New Compounds

Dichroic, pink to blue single crystals of Sr7H12Cl2 and Sr7H12Br2 were obtained by reacting Sr with SrX2 or NaX and NaNH2 or NH4X (X = Cl, Br) as hydrogen sources in a Na melt at 900 °C for 12 h in silica-jacketed stainless-steel or Ta ampoules. The crystal structures of the new compounds were determined by means of single crystal X-ray diffraction. Both title compounds crystallize isotypically to Ba7Cl2F12 in the hexagonal space group P6̅ (no. 174) with the lattice parameters a = 998.06(3), c = 392.84(3) pm for Sr7H12Cl2 and a = 1004.62(3), c = 399.68(3) pm for Sr7H12Br2. The hydride positions taken from the difference Fourier map agree with those of the fluorides of the isotypic compound Ba7F12Cl12. The validity of our structural results is corroborated by EUTAX calculations and the comparison to SrH2, SrX2 and SrHX.

The observation of defects on (100) CdTe surfaces by chemical etching

1992 ◽  
Vol 50 (2) ◽  
pp. 1424-1425
Author(s):  
M.E. Lee
Keyword(s):  
Single Crystal ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Chemical Etching ◽  
Crystalline Perfection ◽  
Crystalline Defects ◽  
High Incidence ◽  
Crystallographic Defects ◽  
Cdznte Substrates ◽  
Device Technology

The crystalline perfection of bulk CdTe substrates plays an important role in their use in infrared device technology. The application of chemical etchants to determine crystal polarity or the density and distribution of crystallographic defects in (100) CdTe is not well understood. The lack of data on (100) CdTe surfaces is a result of the apparent difficulty in growing (100) CdTe single crystal substrates which is caused by a high incidence of twinning. Many etchants have been reported to predict polarity on one or both (111) CdTe planes but are considered to be unsuitable as defect etchants. An etchant reported recently has been considered to be a true defect etchant for CdTe, MCT and CdZnTe substrates. This etchant has been reported to reveal crystalline defects such as dislocations, grain boundaries and inclusions in (110) and (111) CdTe. In this study the effect of this new etchant on (100) CdTe surfaces is investigated.The single crystals used in this study were (100) CdTe as-cut slices (1mm thickness) from Bridgman-grown ingots.

Mounting an individual submicrometer sized single crystal

1996 ◽  
Vol 211 (6) ◽  
Author(s):  
R. B. Neder ◽  
M. Burghammer ◽  
Th. Grasl ◽  
H. Schulz
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Single Crystal ◽  
Single Crystals ◽  
High Vacuum ◽  
Nanometer Resolution ◽  
Micro Manipulator ◽  
Scanning Electron

AbstractWe developed a new micro manipulator for mounting individual sub-micrometer sized single crystals within a scanning electron microscope. The translations are realized via a commercially available piezomicroscope, adapted for high vacuum usage and realize nanometer resolution. With this novel instrument it is routinely possible to mount individual single crystals with sizes down to 0.1

Study of potential oscillations during reaction of an aluminium single crystal with an aqueous KOH solution

1990 ◽  
Vol 55 (2) ◽  
pp. 345-353 ◽  
Author(s):  
Ivan Halaša ◽  
Milica Miadoková
Keyword(s):  
Aqueous Solutions ◽  
Single Crystal ◽  
Single Crystals ◽  
Periodic Potential ◽  
Optimum Conditions ◽  
Potential Oscillations ◽  
Dilute Aqueous Solutions ◽  
Experimental Findings ◽  
Kinetics Of

The authors investigated periodic potential changes measured on oriented sections of Al single crystals during spontaneous dissolution in dilute aqueous solutions of KOH, with the aim to find optimum conditions for the formation of potential oscillations. It was found that this phenomenon is related with the kinetics of the reaction investigated, whose rate also changed periodically. The mechanism of the oscillations is discussed in view of the experimental findings.

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