An oxidation resistant Ti5Si3/NiTi intermetallic matrix composite coating was fabricated on substrate of a titanium alloy BT9 by laser cladding using the Ni - Ti-Si alloy powders. The oxidation resistance of the laser clad intermetallic composide coating was investigated under the testing condition of 1000℃ and 50 hours. The results indicate that the laser clad intermetallic composite coating has a rapidly solidified homogeneous microstruc-ture consisting of Ti5Si3 primary particles uniformly distributed in the Ti5Si3/NiTi eutectic matrix and it is metal-lurgically bonded to the titanium substrate. The isothermal elevated -temperature oxidation resistance of the laser clad intermetallic composite coating is enhanced significantly. Oxidation resistance of the laser clad intermetallic composite coating was up to 1. 79 times higher than that of the original titanium alloy BT9. The oxidation kinetics of the laser clad γ/NiTi intermetallic composite coating is conforming to the parabolic-rate law equation at the testing condition.The excellent oxidation resistance of the coating is mainly attributed tO that the relatively continuous OXide scales which mainly consist of TiO2，A1203 and SiO2 prevented the inner part of the laser clad interm etallic composite coating from being further oxidized．

The metal siliclde MoSi2 is regarded as a promising candidate high-temperature structure material due to its outstanding balance of high melting point (2030℃ ) .lower density(6. 24g/cm3) , excellent oxidation resistance. MoSi2 metal silicide composite coating was fabricated on substrate of nickel- plate by laser cladding using Mo - Si elemental powder blends. Non -equilibrium rapid solidified microstructure was characterized by SEM.XRD and EDS. Microhardness of the composite coating was measured by MH6 semi automatic Vickers hardness tester.

A corrosion resistant Ni31 Si12/FeNi silicides composite coating was fabricated on substrate of a low carbon steel A3 by laser cladding using the Ni, Si powders. The laser clad silicides composite coating, which is met-allurgically bonded to the steel substrate, has a rapidly solidified microstructure consisting of belt-shaped Ni31 Si12 primary phase and small amount of FeNi/N31Si12 eutectics. The average microhardness of the laser clad silicide alloy coating ranges from HV650 to HV750. The corrosion resistances of the nickel silicides composite coating as the content of alloyed-element Cr in the water solutions of 0. 5mol/l H2SO4 were evaluated utilizing the anodic polarization electrochemical corrosion-test method. Because of the inherent excellent corrosion-resisting properties of the constituting phases of Ni31 Si12 and FeNi, and the rapidly solidified homogeneous microstructure, the laser clad nickel silicides composite coating exhibits excellent corrosion resistance. Meantime it is indicated that the corrosipn resistances of laser clad Ni31Si12/FeNi silicides composite coating are enhanced with the increasing chromium content.

Three kinds of coating were prepared by powder feeding type laser cladding using powders consist of self-smelting Co-base alloy with without WC, and self- smelting Ni-base alloy plus WC. Microstructure and hardness at different temperatures of the samples were studied experimentally. The results show that the three samples differ significantly in structure and property under the same laser processing parameters. For the Ni-type alloy, its hardness decreases markedly at 700℃ with an obvious structural changes while for the Co-type alloys, the occurrence of changes starts only at 700℃ .and the extent of the changes with temperatures are smaller. Also, it has been proved that no prodigious change in the hardness of WC can be observed with the rise of temperature. These conclusions provide important reference for the designing of ami- adhesive wear parts.

This paper presents the research on coaxial powder feeding laser cladding of superalloy K403 with a commercial manual-mixed nickel based alloy and a manual-mixed nickel alloy free of boron and silicon. The effects of the substrate microstructure, clad materials and cladding parameters on the tendency to cracking were investigated. The feasibility on the strengthening and repairing of superalloy turbine blades by laser cladding was discussed. The results revealed that laser cladding of nickel based superalloy free of boron and silicon is good for eliminating cracks.

Zr65A17. 5NilOCul7. 5 alloy powers have been cladded on Ti substrate. The coatings constitute of amorphous, intermetallic phases and nanocrystalline. Structure analysis andMicrostructure token show that the crystalline were Zr2Cu,Zr2Ni and A12Zr3. The bonding zone between substrate and coating is composed of columnar crystalline of Ti and a -type solid solution(Ti/Zr)

Ni-based spontaneous melting alloy powder and Co - based spontaneous melting alloy powder are selected for laser cladding on the mild steel substrate with the fore-put powder and the coaxial powder feeding respectively. Laser power is 2. 0 kW, laser beam spot diameter 2. 0 mm,scanning speed 0. 15-0. 25 m/min. The results show that the microstructure of the coaxial powder feeding laser cladding layer is finer than that of the fore-put powder laser cladding layer (the former 2. 5-4. 0 μm, the latter 5. 0-10. 0 μm) .and thermal shock resistance of the former is better than that of the latter. Obviously, this is very significant because the coaxial powder feeding laser cladding is easy to realize automation and big area cladding.

By the means of stainless steel blade using laser surface alloying , laser cladding techniques designs and experimentation, by the analyses of induration's layer microcosmic buildup and induration characteristic analyses, optimize knife edge laser aggrandizement techniques, bring forward that, for thick knife ,adapts to using laser aggrandizement, in allusion to thin knife, adapts to using laser aggrandizement at high speed, at the same time, this technique is applied to kitchen

The CO2 laser quenching treatment was used to study the surface modification of a gear counter. In the present investigation, the two hardening the counter gear approaches were compared by the CO2 laser. It was found that the two approaches of laser quenching were effective to enhance the surface microhardness to HV412 -HV550 . Meanwhile, the microhardness distribution was measured . After the laser heat treatment ,the depth of laser hardening was 1. 0mm, the highest microhardness HV680 was higher HV160 than the common oil quenching. The value of surface roughness before quenching was not found to change with comparison to that after quenching treatment. It is shown that the distortion of surface upon laser quenching was remarkably induced to 2. 5μm. In addition, the microstructure of 3Cr13 stainless steel after laser quenching and high frequency induction quenching was observed. After laser quenching, the fine martensite structure was obtained.

Rapid Laser Forming (RLF) was a new and advanced manufacture technology which has been developed on the base of combining high-power laser cladding technology with rapid prototyping to realize net shape forming of high performance dense metal components without dies. However, such defect as crack, pore, oxidation and ill bonding between cladding layers might appear in RLF parts if the process parameters controlled improperly. And crack was a kind of defect, which was the most familiar and companied with the largest brisance. The forming mechanism of the crack producing in the process of laser forming some alloy powders has been studied deeply in the paper through micro measurement and analysis methods. The results showed that the cracking behavior was different with different cladding materials. For the materials such as nickel-base self-fused alloys the cracking of laser cladding belonged to the cold crack domain. It was the result of synergistic effect of low ductilitv of such a11ovs and thermal stress inducing during laser cladding．On the other hand．for the materials 3S austenite stainless steel etc．the cracking of laser cladding belonged tO the hot crack domain． It was m ainly caused by the separation of the liquid film s in the grain boundary under the effect of thermal stress existed in the cladding which was producing in RIF.

In order to raise the processing efficiency and quality of the larger workpieces, an innovative line scanning selective laser sintering rapid prototyping (SLS RP) process is introduced, differing entirely from the vibrating mirror spot scan. Changing the output beam of CO2 laser into a linear beam by cylindrical lenses, the length of the linear beam on the working plane can be varied from the maximum designed length to a single spot by a zooming unit during scanning. The line width 0. 13mm and variable line length range 0. 13-40mm can be achieved. Laser power and scanning speed are optimized for different line length to sinter the various organic powder materials sufficiently. The processing efficiency and quality of the innovative line scanning system is better than that of the vibrating mirror spot scan for larger workpieces，so the application region of SLS RP technology may be expanded greatly.

In this paper, heat-conduction underwater welding of Type-304 stainless steel with filler wire by using a 4kW Nd: YAG laser was investigated. In underwater welding, the shielding conditions of the local dry cavity have strong influence on the weld bead shape and weld properties. The structure of the nozzle and the gas flow speed are the main factors affecting the stability of the local dry cavity. In specific, appropriate enlarging the outside diameter of the nozzle can obtain perfect shielding condition. If the shielding condition is incomplete, the oxygen content of the weld metal may increase from the normal value of about 80ppm under good shielding condition to800ppm. The increase in oxygen content leads to the severe decrease in the elongation rate and the reduction of area in tensile test, although no variation in tensile strength. Under appropriate shielding condition, the chemical composition and mechanical properties o fthe underwater laser welds can be as same as that in air.

New generation steels have double strength and higher toughness than the normal ferrite steels because of their micrometer or sub-micrometer sized grains. The weldability of the steels is the key for the success of the steels. In this paper SS400 steel is welded by CO2 laser beam and welded joint with higher toughness and strength than the base metal is obtained. When the microstructures of weld metal and coarse-grained HAZ mainly consist of lower bainite the toughness is the highest. When ferrite side plates occur or the microstructures contain high percentage of martensite. the toughness decreases , but is still higher than that of base metal. The hardness of welded joint is lower than Hv330 and there is no softened zone. The welded joint has good bending ductility and its tensile strength is higher than that of base metal.

In this paper, authors introduce the realization of self -adapt of laser cutting parameters when researching on laser intelligent processing. The corner part of work piece can be searched from work piece CAD model in computer, then the dynamic relationship between cutting speed and laser power can be obtained by experimental research. When actual cutting corner part of work piece, the laser power will change depending on cutting speed to avoid the overheat at this position.The satisfying cutting result shows the intelligent laser cutting.

Laser beam welding was used to join SiCp/6063Al composite and Ti was used as in-situ material. The result showed that weld and HAZ are narrow and no pore can be found in weld. The analysis on microstructure of weld center showed that the grain size of weld matrix is very fine and the grains crystallize as equiax crystal, microstructure of weld is very compact and no obvious micro - gaspore and crack are found. No needlelike reaction product A14C3 is observed in weld, which can produce when SiC particles react with matrix during fusion welding. There are many finer TiC particles which are nearly round and the distribution of the particles is even in weld. The whole welding zone turns to be as follow: the base metal is SiC particles reinforced Al matrix composite and the weld is partial zone in which TiC particles are reinforcement and Ti is matrix. The result showed that A14C3 in weld center is restrained completely with Ti as in - situ' weld - alloying materials during impulsed laser beam welding for SiCp/6063 composition and the intensity of jiont is increased due to rapidly solidified phase such as TiC.

Calculations showed that 5 mJ energy was enough to vaporate materials in a pit of 100μm diameter and 10μm depth. When a laser pulse with duration 600ns and energy 10mJ shoot on the surface of metal, the power density is 108 W/cm2 if it was focused on a region of 100μm diameter. This energy was well enough to evaporate iron within 6. 37ns, while plasma plumb was produced. So it was clear that most of laser energy was absorbed by plasma. It was found that major loss of laser energy was inverse bremsstrahlung absorption by plasma. To lower the e-lectron density of plasma, an unique technique was developed to modified laser waveform. When high repetition frequency pulse laser beam radiated on the roller surface, a number of micro-pits were formed, in which metal was melt and solidified. We say the roller was textured. Experiments showed that the tensile strength σb of laser-textured steel sheet increased 4 - 7% than that of shoot-peening steel sheet, and the yield strength σ0. 2 of laser-textured steel sheet decreased 6— 7 than that of shoot- peening steel sheet，the stretchability艿1O increased 6— 1O ．Another advantage of laser— texturing sheet was its good lubricity comparing with shot— peening steel sheet．

With the development of automobile industry, surface roughness of steel sheet for automotive use is one of the most important control items. In this paper, aimed at a new type of roll surface roughness profile (slight protuberance similitude of spherical cap) optimization designed by tribology method, we present a new principle of laser texturing. In the experiment, a pulsed laser beams generated by Nd:YAG laser is adopted to process the roll surface. According to the analysis and investigation of the new principle of laser texturing, the laser parameters are primely selected and matched. Consequently, the surface roughness profile and size have been successfully obtained. Furthermore, we measure and analyze the surface roughness hardness. The results show: the surface roughness has higher hardness rather than matrix. In addition, the influence rules between pulsed laser parameters and main profile parameters of roll have been analyzed and investigated.

This paper presents a novel acoustooptic Q- switch used in laser marking system. The principle design consideration and fabrication processes are given. Experimental results of 50W Q-switch power,over 50% diffraction loss,below 5% of insert loss, 1 - 50KHz modulation frequency at 4mm of the light aperture and 1. 06um wavelength are obtained.

The finite element method is used to calculate the temperature field in the laser heat treatment and the choice of boundary conditions is discussed for the thin plate. The influences of laser power and translation velocity of workpiece have been investigated on the temperature field and compared with the results of semi - analytical method.

Through studying the technology of laser cladding WF218 alloy powder and the properties and micro-structure of the alloy fabricated by laser cladding ,it is obtained that minimum energy density curve changed with the thickness and the widthness of the alloy fabricated by laser cladding and the property of the alloy fabricated by laser cladding . The data is on basis of the users choosing and supplying WF218 alloy powder by laser cladding and the alloy fabricated by laser cladding in the valve .

By means of computer, processing on photos of laser welding plasma taken by high-speed photography at 1000 frame frequency is discussed . The area of welding plasma is calculated by the use of pixel and expressed as quantity of pixels , then the diagram of picture number to plasma area is given out . The ithothermal line based on gray scale is drawn . The propagation affection of laser induced plasma to incident laser is analyzed when the induced plasma is divided into 10 regions with different refractive index, the results show the diverging of laser beam make the induced plasma like negative lens and even welding unable to proceed in sever condition.

Objective:To investigate the influence on the Expression of Fas Protein of CD4 + T Cell in the cases of psoriasis by low level He-Ne laser irradiation. Methods: the expression of CD4 + T Fas protein was determined in the casee of psoriasis(n=5) pre and post-low level laser irradiation(30 min,60min and 120min)by flow cytometry as compared with the control(n=5). Results:In the cases of psoriasis,the expression of CD4 + T FAS protein 21. 4 ±3. 1% was increased significantly than that of control group 16. 8±2. 1% pre -irradiation, p0. 05;in the cases group, the expression of CD4 + T Fas protein wae positivelly corelated to the irradiation times, when the energy density arrived to 22. 92J/cm2(60 minutes)and 45. 84J/cm2(120minutes) , the expression of CD4 + T T Fas protein was increased significantly as compared with pre - irradiation, p<0. 05. Conclusion: The expression of CD4 + T FAS protein may be increased by low level He-Ne laser irradiation，therfor,the uncontrolled status of apoptosis could be corrected.

Objective: To observe the effectiveness of treatment of xanthelasma palpebrarum with ultrapulsed-CO2 laser. Methods: 36 patients of Xanthelasma Palpebrarum (78 periorbital xanthelasmas) were treated with ultra-pulsed CO2 laser (maximal pulse energy 500J/impulse) irradiating on lesions. Results: All lesions could be removed completely with a single laser treatment. After 1 -10 months follow-up time, no visible scarring was observed. 4 patients (11. 11%) developed a recurrence of xanthelasma. Conclusion: The ultrapulsed CO2 laser is an effective and safe therapeutic alternative to all the other surgical procedures.

Objective: This study evaluated the clinical response and side effects during laser tooth bleaching 612 patients. Methods: A rubber dam was placed over the teeth to protect the gum. Laser whitening procedure began when patented gel applied to the teeth. When argon laser energized, the gel acts as a catalyst to whiten the enamel. Results: All the procedure was accomplished in about two hours without pain or other discomfort. Conclusion: Laser whitening is far superior to traditonal bleaching.

Objective: The treatment protocol was designed to assess the efficacy of intracoronal laser teeth bleaching in the treatment of nonvital teeth darkening. Methods: The procedure was much the same with conventional laser teeth bleaching. Gum and lips were protected and bleaching agent was applied on buccal &. lingual surface (including root canal). Results: Teeth received laser bleaching showed 3 - 5 shades whiter. 89% patients had a greater than 85% in the discolorant after an average of 3. 4±0. 75 treatment. Conclusion: Teeth darkening caused by trauma or pulp degeneration are candidate for intracoronal laser teeth bleaching.

80 patients (85 eyes) with lacrimal duct occlusion were treated by Nd:YAG lacrimal laser . The treatment was effective. The efficiency rate was 82. 3%. Nd: YAG laser treatment is a safe and effective method for lacrimal duct occlusion.

Objective:To evaluate the effectiveness of selective laser photocoagulation treatment for the peripheral retinal breaks. Methods:44 eyes in 38 patients of peripheral retinal breaks accompanied with eye flashing or/and vitreous floaters were included in this study, all the eyes were precluded visual defect and extensive retinal degeneration over 2 quadrants. Double or triple rows of argon laser burns were applied around or behind the posterior rim of the lesion if it was too peripheral. Results: During the mean follow-up period of 16 months, no change in visual acuity and visual field was noted after treatment as compared with those of before treatment in 43 eyes, and no complication was observed in these eyes. The subretinal fluid progressed in 1 eye so the cryopexy and scleral buckling surgery were intervened. Conlusion: Laser photocoagulation is an efficacious method to treat the peripheral retinal breaks and degenerations . Complications could be reduced to a minimum in selective patients.

Objective: In order to analyse the safe and security of CO2 Laser with silver halide optial fibers which made by Shanghai in stiute of Ceramics, Academia. Methods: 128 cases which involving skin, mouth, cervix, sig-moid colon, rectum and anal canal were treated by CO2 Laser with silver Halide optical fibers. The tissue were vapoured and cabonized by CO2 Laser. Results: After a certain period of time's follow-up and obervation. the results were found with satisfactory, which assures us that this kind of treatment has the feature of stable output officiency, reliable safety easy to handle and it meets the require ments of a successful obervation. During the 3 month' s followup and obervation, the recovery rate is up to 97%. Couclusion: The CO2 laser with silver halide optial fibers has the best quality. It meets the require meat of successful iperation. It is suitable for the therapy of endocavity in the end.

Objective: To investigate the side effects of 585nm pulsed dye laser in treatment of the vascular abnormalities. Methods: We analysed the side effects of 500 cases treated by 585nm pulse dye laser. Results: There were 89 cases occuring side effects in 500 cases patients, pigmentation 35 cases, pigment droping 12 cases,atrophic scar 40 cases, hyperplastic scar 2 cases. Occuring of side effects have nothing to do with the types of disease and the energy of treatment, It is relevant to frequency of treatment. Conclusion; The 585nm pulsed dye laser haven't side effects of hyperplastic scar and continued pigmentation treated by continuous lasers, It's safe in treating vascular abnormalities.

The results of Q-witched laser with varied length in the treament of 70 cases complicated eyebrow tattoos were reported. The rate of cure was 100%. The method marked therapeutic effect in removal of tattoo pigment without causing scar formation or hair follicle damage. It is an excellent therapeutie procedure for the removal of eyebrow tattoos, and has more advantges than the current routine methods.

To evaluate the therapeutic effectiveness of homemadeQ - switched Nd: YAG laser irradiation in treatment of 62 cases tattoo Complete removal of tattoo was achievdin 49 cases, good effect in 13 cases. No scar left behind. A transient pigmeatation occured in a few patients, which all regressed in 3-5 months.

In order to study the methods and effects of gastrohelcovsis treated by Nd:YAG laser between 1997 to 1998. The Nd:YAG laser were led into the ulcer lesion through the gastroscope directly. Nd: YAG laser exposure power was 50W. The times of irradiaion were various according to the area whether large or small of the ulcer. 8 of the 32 cases were one single ulcer lesion. 24 of the 32 cases were multiple ulcer lesions. The results of the study indicated that the rate of healing was 100%. No side effect or complication was found in the study 26 of 32 cases were not observed recurrence ulcer after one year.

Objective: To investigate the effect of low power density laser irradiation on cytoplasmic free calcium concentration and the change of plasma membrane Ca2+ - Mg2+ - ATPase activity of human peripheral blood lymphocytes. Methods: Human peripheral blood lymphocytes, in vitro, randomized into irradiated group or control group. Lymphocytes were exposed to low power density He-Ne laser for 15, 30, 60min, and then the cytoplasmic free calcium concentration in human peripheral blood lymphocytes were measured by fluorescent indicator Fura-2/ Am estimating technique and the change of plasma membrane membrane Ca2+ - Mg2+ - ATPase activity in lymphocytes were measured by Lowry's technique. Results: The concentration of intracellular plasmic free calcium was lower in irradiated group than in control group (P<0. 05) , and the activity of plasma membrane Ca2+ -Mg2+ -ATPase increased significantly. Those changes reduced along with the length of exposing time. It showed that the concentration of intracellular free calcium correlated with the change of plasma mem brane Ca 一M g 一ATPase activity．Conclusion!The acticity of plasm a m embrane Ca 一M g ～ ATPase was activated by low power density laser irradiation of certain energy，and then followed by the change of perm eability of plasma membrane，influencing the change of storage of intracellular free calcium and the change of permeability of cell membrane and also cellular function

This paper measured output power density of He-Ne Laser and radiance of cavity resonatort and analysed its irradiation damage on the basis of maximum permissible exposure (MPE) of eye and skin. In the end, some protections were proposed.

Under intravenous low level laser irradiation (ILLLI) of semiconductor green laser and He-Ne laser , we observed the SOD and LPO level of blood and its sustained effects so as to give some experiment data as theoretical evidence of clinical application. The results indicated that the density of SOD had a significant increase and the density of LPO had an apparent decrease after the irradiation. The effects caused by green laser were more obvious than those caused by He-Ne laser.