Microhardness of the Surface Layer of Tungsten and Molybdenum After Recrystallization With Laser Radiation

1991 ◽  
Vol 113 (1) ◽  
pp. 130-134 ◽  
Author(s):  
F. Kostrubiec ◽  
M. Walczak
Keyword(s):  
Surface Layer ◽  
Laser Radiation ◽  
Laser Beam ◽  
Single Pulse ◽  
Glass Laser ◽  
Multiple Pulse ◽  
And Tungsten

We present results of microhardness measurements in melted local regions in molybdenum and tungsten. Microhardness has been measured by the Vickers method. Melted regions have been produced by pulsed Nd-glass laser. The emphasis is on correlation between conditions of recrystallization (energy of laser beam and method of irradiation-single pulse or multiple pulse) and the microhardness value.

scholarly journals Modeling Perfusion Dynamics in the Skin During Iontophoresis of Vasoactive Drugs Using Single-Pulse and Multiple-Pulse Protocols

2015 ◽  
Vol 22 (6) ◽  
pp. 446-453 ◽  
Author(s):  
Fredrik Iredahl ◽  
Veeranjaneyulu Sadda ◽  
Liam J. Ward ◽  
Johannes Hackethal ◽  
Simon Farnebo ◽  
...  
Keyword(s):  
Single Pulse ◽  
Vasoactive Drugs ◽  
Multiple Pulse

scholarly journals Temperature Calibration Measurements based on Laser-Induced Phosphorescence Technique for Combustion Applications

2015 ◽  
Vol 10 (1) ◽  
Keyword(s):  
Laser Radiation ◽  
Laser Beam ◽  
Intensity Ratio ◽  
Laser Power ◽  
Room Temperature ◽  
Pulsed Laser ◽  
Temperature Calibration ◽  
Phosphor Powder ◽  
Calibration Methods

Phosphor powder and phosphor-binder mixtures are successfully employed for temperature calibration measurements by using laser-induced phosphorescence (LIP) technique with an emphasis on higher precisions and accuracies than other non-intrusive methods. The phosphorescence intensities are used to perform these calibrations in three different strategies. The influence of laser power regular changes on particles heating and the calibration analyses is also carried out. A pulsed laser at 355 nm was used for exciting specimens of the phosphor powder as well as the phosphor-binder mixtures. The laser beam was directed onto the specimens and varied in three laser power levels (LPLs). The samples were kept in an oven with temperatures ranging from room temperature up to 1800 °C. The three strategies which are expressed in terms of non-dimensional intensity versus wavelength (NDI-W), normalised intensity (NI) and intensity ratio (IR) were used for the calibration assessments. A modified IR was compared with two different IRs. A precision of around ± (0.50-1.41)% was attained for different calibration methods. This research confirmed that these calibrations are possible using three different strategies, given high precisions and accuracies. The laser power alternations influenced the NI and do affect neither the NDI-W nor the IR curves. The laser radiation does not play any role for heating the particles of the studied powder.

scholarly journals INCREASING THE EFFICIENCY OF SURFACE STRENGTHENING OF METAL PRODUCTS BY COMBINED THERMODEFORMATION PROCESSING

2020 ◽  
pp. 103-110
Author(s):  
Oleksandr Danyleiko ◽  
Vitaliy Dzhemelinskyi ◽  
Dmytro Lesyk ◽  
Artemii Bernatskyi
Keyword(s):  
Surface Layer ◽  
Laser Beam ◽  
Surface Hardening ◽  
Thermal Deformation ◽  
Experimental Studies ◽  
Numerical Control ◽  
Surface Plastic ◽  
Beam Diameter ◽  
Metal Products ◽  
Deformation Surface

The article discusses the prospects of using combined thermal deformation surface processing to improve the performance properties of metal products. There is a new method of thermal deformation surface hardening (shot peening (SP) followed by laser heat treatment (LHT)) for tools and crown housings operating under difficult conditions proposed. For carrying out experimental studies, flat samples of 30KhGSA steel and steel 45 were selected. Preliminary hardening and finishing with static or dynamic methods of surface plastic deformation were carried out on a modernized installation based on a DYNAMITE 2800 numerical control machine, and SP was implemented on industrial equipment. Laser surface hardening of the samples was carried out in single passes with a sample moving speed of 300...500 mm/min with a laser beam diameter of 7.3 mm and a laser power of 1 kW using the ROFIN-SINAR DY 044 technological unit. The optimal regimes of surface hardening are determined under the deformation action of a gas-dynamic flow with solid particles and thermal action by a laser beam to obtain maximum values ​​of hardening depth and hardness. In particular, with SP, the gas-feed stream feed pressure is 0.5 MPa, the processing time is 1 min, regardless of the type of material. The optimal laser beam power is 1 kW at a sample travel speed of 300 mm/min. There are the results of experimental studies of the change in the hardening depth as a function of time and pressure after SP, the speed of movement of the treated sample from carbon steel 45 and medium alloyed steel 30KhGSA after LHT and combined SP+LHT, and also the distribution of microhardness over the depth of the hardened layer presented. It is revealed that the combined SP+LHT of 30 KhGSA steel at optimal modes forms 1.5 times (1.3 mm) greater depth of the strengthened surface layer in comparison with LHT, while providing the surface layer hardness of ~5400 MPa.

Measuring Method of Transverse Mode in a Laser Beam Based on Spatial Distribution of Single Pulse Energy

2010 ◽  
Vol 39 (11) ◽  
pp. 2040-2044
Author(s):  
周娜 ZHOU Na ◽  
王石语 WANG Shiyu ◽  
过振 GUO Zhen ◽  
蔡德芳 CAI Defang ◽  
文建国 WEN Jianguo ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Laser Beam ◽  
Pulse Energy ◽  
Single Pulse ◽  
Transverse Mode ◽  
Measuring Method ◽  
Single Pulse Energy

Corrosion characterisation of laser beam and tungsten inert gas weldment of nickel base alloys: Micro-cell technique

2015 ◽  
Vol 93 ◽  
pp. 1-8 ◽  
Author(s):  
Geogy J. Abraham ◽  
V. Kain ◽  
G.K. Dey ◽  
V.S. Raja
Keyword(s):  
Laser Beam ◽  
Inert Gas ◽  
Nickel Base ◽  
And Tungsten

Multiple Pulse Irradiation Effects in Excimer Laser-Induced Crystallization of Amorphous Si Films

1993 ◽  
Vol 321 ◽  
Author(s):  
H. J. Kim ◽  
James S. Im
Keyword(s):  
Excimer Laser ◽  
Single Pulse ◽  
Pulse Irradiation ◽  
Multiple Pulse ◽  
Melting Phenomenon ◽  
Irradiation Energy ◽  
Crystallization Experiments ◽  
Amorphous Si ◽  
Si Films ◽  
Induced Crystallization

ABSTRACTWe have experimentally Investigated the effects that are associated with Multiple-pulse irradiation in the excimer laser processing of thin Si films on SiO2. Double-pulse irradiation experiments revealed results, which are consistent with that which is known from single-pulse crystallization experiments, and these experiments confirm the applicability of the transformation scenarios, which were derived from single pulse-induced crystallization experiments [1,2]. The results from the Multiple-pulse irradiation experiments clearly show that gradual and substantial grain enlargement can occur — and only occurs — when the irradiation energy density is close to but less than the level that is required to melt the film completely. Based on these findings, we argue that the grain enlargement effect is a near-complete melting phenomenon that is associated with polycrystalline Si films, and we present a grain boundary melting model to account for this phenomenon. A brief discussion on the apparent similarities and physical differences between the observed phenomenon and the solid state grain growth processes is provided herein.

Micro and Nanofabrication of GaN by Wet-Chemical-Assisted Femtosecond Laser Ablation

2009 ◽  
Author(s):  
Seisuke Nakashima ◽  
Koji Sugioka ◽  
Katsumi Midorikawa
Keyword(s):  
Laser Ablation ◽  
Laser Beam ◽  
Second Harmonic ◽  
Single Pulse ◽  
Photon Absorption ◽  
Light Extraction Efficiency ◽  
Objective Lens ◽  
Uniform Size ◽  
Fs Laser ◽  
Wet Chemical

For micro/nanofabrication of Gallium nitride (GaN), we developed wet-chemical-assisted fs laser ablation in which the femtosecond (fs) laser beam focused using an objective lens was directed on the surface of a GaN substrate immersed in 35% hydrochloric (HCl) acid solution. Nanocrators with a diameter as small as 320 nm (FWHM) were successfully formed on surface of a single-crystal GaN substrate by a single pulse of the second harmonic fs-laser beam (λ = 387 nm, 150 fs) focused using an objective lens with NA of 0.5. Nano scale ablation is responsible for two-photon absorption of the fs laser. The ablated craters exhibit higher quality and better uniformity with little debris formation compared with those produced by fs-laser ablation in air followed by etching in HCl (two-step processing method). The high quality ablation is presumably due to photochemical or photothermal reaction of HCl solution with ablated materials, resulting in complete removal of debris and in sharp edge and smooth surface of craters. We have demonstrated formation of 140-μm-long straight and hollow channels embedded in GaN by scanning the laser beam inside the substrate. 3D micro and nano fabrication technique of GaN has great potential for manufacture of highly-functional micro devices. We have also tried to fabricate 2D periodic nanostructures on GaN surface by scanning the sample in x-y plane. Nanocrators with uniform size periodically arranged on GaN surface can act as a two-dimensional (2D) photonic crystal which is expected to enhance a light extraction efficiency of blue LED.

scholarly journals The analysis of friction properties after laser texturizing of the silicon carbide surface layer

2018 ◽  
Vol 183 ◽  
pp. 02010
Author(s):  
Norbert Radek ◽  
Agnieszka Szczotok ◽  
Renata Dwornicka
Keyword(s):  
Silicon Carbide ◽  
Surface Layer ◽  
Statistical Analysis ◽  
Design Of Experiments ◽  
Laser Beam ◽  
High Reliability ◽  
Laser Beam Machining ◽  
Before And After ◽  
High Roughness ◽  
Modification Of The Surface

The modification of the surface properties is a desired technological procedure. One of the possible method is the electro-spark deposition (ESD). Unfortunately, ESD process produces a surface with high roughness. The laser beam machining (LBM) has been involved to lower roughness of the coating made by ESD. The elements coated by ESD have been tested to determine tribological properties and they were compared before and after LBM. To achieve high reliability of the results, the test has been conducted in accordance with design of experiments methodology and the results which were obtained have been processed by a statistical analysis. The description of such an experiment performed for a silicon carbide SiC coating, the obtained results and the conclusions are included in this paper.

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