The morphologies of Ni-based WC coating by flame spraying and laser cladding respectively were observed with
scanning electric microscope (SEM), respectively, and residual stresses were measured with XRD (X-ray diffraction). At
the same time, the spectra of WC coating were analyzed by XRD, and the forming mechanisms of residual stress were
analyzed. Experimental results are shown that residual stresses of Ni-based WC coating by flame spraying are all
tensile while those by laser cladding are compressive, chemical-physical reaction of the coating is the cause to result in
material volume change, which makes residual stress into compressive from tensile; when residual stress is changed into
compressive from tensile, micro-cracks on the coating surface greatly decrease, which is illustrated that the effect of
residual stress on micro-crack is obvious; XRD spectra peak of WC coating is only contained Ni and W, and has no
impurity and other reaction productions.
The influences of processing parameters on laser-induced shock waves in metal components are discussed and analyzed. The effects of different parameters of laser shock processing (LSP) on residual stress of aerospace aluminum alloy LC4 were investigated. LSP was performed by using an Nd: glass phosphate laser with 23 ns pulse width and up to ~45 J pulse energy at power densities above GW/mm-2. Special attention is paid to the residual stresses from laser shock processing. Modification of microstructure, surface morphology by laser shock processing is also discussed. Results to date indicate that laser shock processing has great potential as a means of improving the mechanical performance of components.
KEYWORDS: Laser processing, Laser welding, Scanning electron microscopy, X-rays, Crystals, Diffraction, Polishing, Statistical modeling, High power lasers, Laser systems engineering
The surface of AISI304 TIG welding line was processed by LSP (laser shock processing). The effects on the microstructure, hardness and residual stress of AISI304 welding line by LSP were observed, and its mechanical properties were researched by SEM (scanning electron microscope) and test device of mechanical property. Residual stresses of AISI304 TIG welding line by LSP were measured with Model X-350A X ray analyzer. The test results show that compressive residual stress values of AISI304 TIG welding line by LSP are about 110MPa. Strengthening effects of AISI304 TIG welding line by LSP is very obvious, and fatigue properties of welding line is improved, and tensile residual stresses of welding line are obviously reduced, the distribution of residual stress tends to equality, and service life of AISI304 TIG welding line is improved.
Titanium nitride films are deposited on AISI 304 steel with a hollow-cathode-discharge (HCD) ion-plating technique. The status of residual stresses in TiN thin film coated on AISI304 substrate by HCD is studied by x-ray diffraction stress analyzer. By analyzing morphology of the residual stress of TiN thin film at interface between TiN film and AISI 304 substrate, the adhering mechanism of TiN thin film is understood as follows: the mechanical interlocking had important contribution to the adhesion strength, the thermal stress is the major factor which resulting TiN thin film peeling off spontaneously. The results show that the value of thin film is -210MPa~-650Mpa, and the thermal stress is compressive, the intrinsic stress is tensile, origins of the residual stress are primarily discussed.
Parameters and mechanisms of cleaning rubber layer from a rubber sulfuring mould with CO2 laser are analyzed. Laser cleaning is a non-abrasion way, and it can improve mould service life. There are cleaning threshold and damage threshold in laser cleaning, and cleaning percentage of the surface increases with laser power density. The effects of laser parameters on cleaning and performance of the cleaned surfaces are studied. The results show that pulse laser can remove rubber layer completely under proper parameters when the value of laser cleaning threshold is 5~35J/cm2, and no damages are found on substrate surface, mould abrasion that is cleaned by laser decreased.
Laser shock forming(LSF) is a new forming technique of sheet metal by applying a compressive shock wave on the surface of metal sheet. The plastic deformation of TA2 titanium metal sheet is performed under single laser shocking perpendicularly with Nd:Glass laser developed in Jiangsu University. The residual stress state in the horizontal and diagonal direction of the foursquare specimen, as well as the residual stress state in the radial direction of the circular specimen, was investigated with X-ray stress analyzer. The residual stress state of laser shock forming specimen is unique to some extent by contrast with traditional punch forming, which is influenced by the specimen shape and the deformation rate. The experiment results show that residual stresses value of TA2 Titanium Sheet Metal in laser shock area are up to 100MPa.Square specimen is more difficult to be formed than circular specimen, and the press value of cave is the larger than the one of convex.
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