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Zhang H.,Changchun University of Science and Technology | Shi Y.,Changchun University of Science and Technology | Kutsuna M.,Advanced Laser Technology Research Center Co. | Xu G.J.,Shenyang University of Technology
Nuclear Engineering and Design | Year: 2010

Stainless steels are widely used in nuclear power plant due to their good corrosion resistance, but their wear resistance is relatively low. Therefore, it is very important to improve this property by surface treatment. This paper investigates cladding Colmonoy 6 powder on AISI316L austenitic stainless steel by CO 2 laser. It is found that preheating is necessary for preventing cracking in the laser cladding procedure and 450 °C is the proper preheating temperature. The effects of laser power, traveling speed, defocusing distance, powder feed rate on the bead height, bead width, penetration depth and dilution are investigated. The friction and wear test results show that the friction coefficient of specimens with laser cladding is lower than that of specimens without laser cladding, and the wear resistance of specimens has been increased 53 times after laser cladding, which reveals that laser cladding layer plays roles on wear resistance. The microstructures of laser cladding layer are composed of Ni-rich austenitic, boride and carbide. © 2010 Elsevier B.V. All rights reserved. Source

Xu G.,Shenyang University of Technology | Zhong L.,Shenyang University of Technology | Wang H.,Tenneco | Fu X.,Anshan Raycham Technology Co. | And 2 more authors.
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2014

In the present work, laser shock processing (LSP) using a Q-switch YAG laser facility with high pulsed peak power under water environment is implemented near the toes of A6061-T6 Aluminum alloy metal-inert gas (MIG) welded joints. And the properties of A6061-T6 aluminum alloy MIG welded joints is analyzed before and after laser shock processing through the comparative method. The results show that after laser shock processing, Vickers hardness and fatigue life of the welded joints have been significantly improved, fatigue fracture of the welded joint without laser shock processing is located in or near the welded while it is located on the base material after laser shock processing, and a larger near-surface residual compressive stress with a maximum value of about -145 MPa is obtained. Compared with the base material, the surface roughness deteriorates after laser shock processing. Source

Xu G.,Shenyang University of Technology | Zhong L.,Shenyang University of Technology | Hang Z.,Shenyang University of Technology | Zhang C.,Anshan Raycham Technology Co. | And 2 more authors.
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2014

In order to improve the mechanical properties of aluminum alloy welded joints, this paper respectively applied ultrasonic and Q-switch YAG laser shock processing on the weld toe of A6061-T6 aluminum alloy welded joints to study the performances of aluminum alloy welded joints after shock processing. Under two shock processing modes, the near surface on weld toe of aluminum alloy welded joints generated shock strengthening effect, and greater compressive residual stress was produced. The maximum compressive residual stresses generated by ultrasonic and laser shock processing were about -158 MPa and -145 MPa, respectively. The fatigue life of aluminum alloy welded joints after ultrasonic and laser shock processing was similar, increased more than one time compared to that of the welded specimen without shock processing. All specimens during fatigue test fractured in the base metal, and no fatigue crack occurred near the weld toe. Source

Iwata H.,Aichi Institute of Technology | Kutsuna M.,Advanced Laser Technology Research Center Co. | Okuno T.,EcoTopia Science Institute | Saka H.,Aichi Institute of Technology
Philosophical Magazine Letters | Year: 2016

Recently, it was found that the dissociation distance of glide set dislocations introduced in Si just below the melting temperature by laser shock peening (LSP) is unusually wide (Iwata et al. J. Jpn Inst. Met. Materi.,79(2015),308–314). In order to distinguish whether or not this is to be attributed to uncorrelated motions of leading and trailing Shockley partials or the intrinsic temperature dependence of the stacking fault energy (SFE), dislocations introduced by LSP were annealed at 1350 °C, which should be high enough for the uncorrelated partials to assume the equilibrium correlated configuration. It was found that this unusual widening of a dissociated dislocation introduced by LSP is attributed to uncorrelated motions of Shockley partials. Following this conclusion, the temperature dependence of the intrinsic SFE of Si was determined on correlated dissociated dislocations up to near the melting temperature. The intrinsic SFE of Si shows only negligibly small temperature dependence from 400 °C up to near the melting temperature. © 2016 Informa UK Limited, trading as Taylor & Francis Group Source

Iwata H.,Aichi Institute of Technology | Kutsuna M.,Advanced Laser Technology Research Center Co. | Saka H.,Aichi Institute of Technology
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2015

Surfaces of {100} Si wafers were laser-peened in water by a Q-switch YAG laser with an energy density φo ranging from 1 to 10 GW/cm2. To start with, morphology of the ablated surfaces was analyzed by a 3-dimensional optical microscope. When the energy density φo is higher than 5 GW/cm2, macroscopic cracking did not take place. Therefore, on three samples irradiated with φo = 2,3 and 5 GW/cm2, defect structures in the sub-surface layers were examined by transmission electron microscopy compre-hensively. When φo = 2 GW/cm2, the ablated surface was quite smooth and no extensive damage was introduced in the sub-surface region. However, close inspection showed that a subsurface layer about 200 nm thick contained a considerable density of small bubbles and a small number of dislocations running vertically towards the ablated surface. When φo = 3 GW/cm2, the sub-surface damaged layer became more profound with a much higher density of small bubbles and dislocations. On top of this, a considerable density of much larger bubbles were formed, on the inside-wall of which quite a high density of fine crystalline particles were attached. It is concluded that these bubble-containing layer must have been melted on laser irradiation. The bubbles must have been vapor Si formed in the liquid Si, which condensed on the inner wall on cooling. The vertical dislocations are misfit dislocation formed on solidification of the molten Si. However, in the matrix of Si underneath dislocations were rarely observed. This indicates that that region of Si that remained crystalline during the laser irradiation did not receive a stress strong enough to induce dislocations even at a high temperature just below the melting point. When φno = 5 GW/cm2, underneath the bubble-containing layer a high density of dislocations were introduced. However, most of these dislocations appeared different from the ordinary 1/2<110>{111} dislocations. Electron diffraction showed no evidence of the high-pressure phases. © 2015 The Japan Institute of Metals and Materials. Source

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