Map
WeChat
Email alert
RSS2002 Vol. 26, No. 5
Display Method:
2002, 26(5): 321-323,333.
[Abstract]
[PDF 210KB]
Abstract:
In order to explain the relationship among the powder feeding rate,scanning speed and the qualities of the clad coatings,the concepts of the specific energy input Er and the specific energy Eh formulated by L.C.Lim have been introduced with their experimental measuring methods which have been proved be successful.Based on metallographical measurement,the equations expressing the relationship between the specific energy input Er,the specific energy Eh and the parameters of the laser coated layer and the processing parameters has been derived.The factors effecting the specific energy input Er and the specific energy Eh have been studied carefully.When the powder feeding rate vf and scanning speed vs increase,the specific energy Er and the specific energy Eh decrease under definite laser power P and beam spot dimension.A reasonable explanation why a minimum is observed in the relationship between the scanning speed and the specific energy Er is presented.In the meantime,it is the theoretical foundation for further study the microstructure,mechanism of solidification and processing parameters.
In order to explain the relationship among the powder feeding rate,scanning speed and the qualities of the clad coatings,the concepts of the specific energy input Er and the specific energy Eh formulated by L.C.Lim have been introduced with their experimental measuring methods which have been proved be successful.Based on metallographical measurement,the equations expressing the relationship between the specific energy input Er,the specific energy Eh and the parameters of the laser coated layer and the processing parameters has been derived.The factors effecting the specific energy input Er and the specific energy Eh have been studied carefully.When the powder feeding rate vf and scanning speed vs increase,the specific energy Er and the specific energy Eh decrease under definite laser power P and beam spot dimension.A reasonable explanation why a minimum is observed in the relationship between the scanning speed and the specific energy Er is presented.In the meantime,it is the theoretical foundation for further study the microstructure,mechanism of solidification and processing parameters.
2002, 26(5): 324-326.
Abstract:
Laser clad Ni based alloy coating with 20%(vol%)SiC(NiSiC) on 16Mn steel substrate has been obtained by 5kW CO2 continuous wave laser implement. Microstructure morphology and phase structure of the laser clad alloy coating have been studied,and microhardness and the performance of sliding wear test of the coating have been discussed in contrast to laser clad Ni-based alloy coating(Ni60). The result shows that the microstructure of laser clad alloy coating is consisted of γ dendrite solid solution and the eutectic structure between the dendrites. Constituent phases of the coating mainly have γ-Ni,γ-(Fe,Ni),(Cr,Fe)7C33,Cr23C6 and (Cr,Si)3Ni3Si. Microhardness and sliding wear resistance of the NiSiC coating are higher than that of the Ni60 coating.
Laser clad Ni based alloy coating with 20%(vol%)SiC(NiSiC) on 16Mn steel substrate has been obtained by 5kW CO2 continuous wave laser implement. Microstructure morphology and phase structure of the laser clad alloy coating have been studied,and microhardness and the performance of sliding wear test of the coating have been discussed in contrast to laser clad Ni-based alloy coating(Ni60). The result shows that the microstructure of laser clad alloy coating is consisted of γ dendrite solid solution and the eutectic structure between the dendrites. Constituent phases of the coating mainly have γ-Ni,γ-(Fe,Ni),(Cr,Fe)7C33,Cr23C6 and (Cr,Si)3Ni3Si. Microhardness and sliding wear resistance of the NiSiC coating are higher than that of the Ni60 coating.
2002, 26(5): 327-329.
Abstract:
Nd:YAG laser alloying Ni-Ti with pre placed coating on specific cylinder bore gray cast iron was investigated and smooth surface alloyed layers were available.This kind of laser alloying cast iron was quite sensitive to cracking.Crack free alloyed layers were possible with appropriate coating thickness,alloying parameters and preheating.The alloyed layer consists of alloyed zone,remelting zone and quenching zone,whose micro hardness is increased dramatically.The main microstructure of the alloyed layer is the hypoeutectic sub-stable structure.
Nd:YAG laser alloying Ni-Ti with pre placed coating on specific cylinder bore gray cast iron was investigated and smooth surface alloyed layers were available.This kind of laser alloying cast iron was quite sensitive to cracking.Crack free alloyed layers were possible with appropriate coating thickness,alloying parameters and preheating.The alloyed layer consists of alloyed zone,remelting zone and quenching zone,whose micro hardness is increased dramatically.The main microstructure of the alloyed layer is the hypoeutectic sub-stable structure.
2002, 26(5): 330-333.
Abstract:
The principle and implements of laser perforating tipping paper technology were discussed in this paper.The results of perforating tipping paper with one of the implements are presented.The factors that influence the permeability of the perorated tipping paper are discussed.
The principle and implements of laser perforating tipping paper technology were discussed in this paper.The results of perforating tipping paper with one of the implements are presented.The factors that influence the permeability of the perorated tipping paper are discussed.
2002, 26(5): 334-337.
Abstract:
A CO2 continuous wave laser with defocused beam is used for laser remelting (LR) the surface of plasma sprayed (PS) thermal barrier coatings (TBCs) on GH536 superalloy substrate. The thermal shock tests are conducted to both PS samples and LR samples. With the different failure criterions,the mechanism of failure is discussed. It is indicated that the higher laser energy input is harmful for thermal shock lifetime of LR TBCs. The thin remelted thickness and improved laser beam quality are suggested for laser plasma compound preparation of TBCs.
A CO2 continuous wave laser with defocused beam is used for laser remelting (LR) the surface of plasma sprayed (PS) thermal barrier coatings (TBCs) on GH536 superalloy substrate. The thermal shock tests are conducted to both PS samples and LR samples. With the different failure criterions,the mechanism of failure is discussed. It is indicated that the higher laser energy input is harmful for thermal shock lifetime of LR TBCs. The thin remelted thickness and improved laser beam quality are suggested for laser plasma compound preparation of TBCs.
2002, 26(5): 338-340,343.
Abstract:
Based on the solution about Fresnel Kirchoff diffraction integral equation and the viewpoint about maintaining the fundamental mode oscillating,an expression which can directly describe relation about the least distinguishable wavelength interval of the tunable laser and the grating resonator parameters,the grating parameters is put forward,and the expression is conformed with experimental results.
Based on the solution about Fresnel Kirchoff diffraction integral equation and the viewpoint about maintaining the fundamental mode oscillating,an expression which can directly describe relation about the least distinguishable wavelength interval of the tunable laser and the grating resonator parameters,the grating parameters is put forward,and the expression is conformed with experimental results.
2002, 26(5): 341-343.
Abstract:
Coupled with the 3-beam laser Doppler anemometry(LDA),the amendment of the measuring parameters in different media was discussed in theory. And the amendatory formulas were achieved. With the formulas,the parameters both in air and in water were obtained and compared. The result proved the amendment of the parameters was correct and necessary. The mean velocities were gained individually in the reduction fluid by LDA and flowmeter. By comparing the two results,it proved the LDA was trustiness.
Coupled with the 3-beam laser Doppler anemometry(LDA),the amendment of the measuring parameters in different media was discussed in theory. And the amendatory formulas were achieved. With the formulas,the parameters both in air and in water were obtained and compared. The result proved the amendment of the parameters was correct and necessary. The mean velocities were gained individually in the reduction fluid by LDA and flowmeter. By comparing the two results,it proved the LDA was trustiness.
2002, 26(5): 344-345.
Abstract:
The preparation of Fe-N compound has been studied with laser nitridation method,based on it,local laser nitridation on the oriented silicon steel has been achieved.The samples have been analysed with XPS method.The results show that Fe-N compounds can be formed under some parameters(laser power,scan speed etc.).Fe-N compounds can be achieved on the surface of grain oriented silicon steel by controlling scan speed,scan space and N2 velocity.The observations with domain observation equipment show that domain of the grain oriented silicon steel has been refined after the nitridation treatment,therefore,the total loss of grain oriented silicon steel can be decreased.
The preparation of Fe-N compound has been studied with laser nitridation method,based on it,local laser nitridation on the oriented silicon steel has been achieved.The samples have been analysed with XPS method.The results show that Fe-N compounds can be formed under some parameters(laser power,scan speed etc.).Fe-N compounds can be achieved on the surface of grain oriented silicon steel by controlling scan speed,scan space and N2 velocity.The observations with domain observation equipment show that domain of the grain oriented silicon steel has been refined after the nitridation treatment,therefore,the total loss of grain oriented silicon steel can be decreased.
2002, 26(5): 346-349.
Abstract:
A new design method to optimize a laser resonator is presented.Applying a genetic algorithm and taking a laser output power as an objective function,we optimize a typical CO2 laser resonator with a length of 1.2m.The optimal laser output with a fundamental mode increases to 89W comparing with the non optimized laser output of 55W,and the measured output increases to 74W in an experiment.
A new design method to optimize a laser resonator is presented.Applying a genetic algorithm and taking a laser output power as an objective function,we optimize a typical CO2 laser resonator with a length of 1.2m.The optimal laser output with a fundamental mode increases to 89W comparing with the non optimized laser output of 55W,and the measured output increases to 74W in an experiment.
2002, 26(5): 350-353,356.
Abstract:
Ca4GdO(BO3)3(GdCOB) is a new self frequency doubling(SFD) crystal. Using xenon lamp as pump sources,we have realized the free run from 1061nm to 530.5nm in SFD Cr:Nd:GdCOB(bi-doped) crystal and Nd:GdCOB(uni doped) crystal.The threshold energies for uni doped crystal and bi doped crystal are 1.0J and 0.92J,respectively;and the maximum output energies of green laser for two kinds of crystals are 1.96mJ and 2.46mJ,respectively. By using pulsed dye laser as pump source,we have obtained SFD red laser at 655nm and its fundamental frequency laser at 1331nm as well as achieved SFD green laser at 530.5nm from a Nd:GdCOB crystal.
Ca4GdO(BO3)3(GdCOB) is a new self frequency doubling(SFD) crystal. Using xenon lamp as pump sources,we have realized the free run from 1061nm to 530.5nm in SFD Cr:Nd:GdCOB(bi-doped) crystal and Nd:GdCOB(uni doped) crystal.The threshold energies for uni doped crystal and bi doped crystal are 1.0J and 0.92J,respectively;and the maximum output energies of green laser for two kinds of crystals are 1.96mJ and 2.46mJ,respectively. By using pulsed dye laser as pump source,we have obtained SFD red laser at 655nm and its fundamental frequency laser at 1331nm as well as achieved SFD green laser at 530.5nm from a Nd:GdCOB crystal.
2002, 26(5): 354-356.
Abstract:
The effect of CeO2 on the macro quality,microstructure and micro hardness of Ni/WC cladding layer has been studied.The results indicate that incorporation of CeO2 can greatly refine the microstructure,reduce the crack tendency and improve the micro quality of the Ni/WC cladding layer.The refine effect becomes more evident with increasing CeO2 content.When CeO2 content is increased to 0.16wt%,the micro hardness reaches its maximum of ca.900HV0.3～1300HV0.3 and cracks vanish.Laser power affects the macro quality,microstructure and micro hardness of the cladding layer also.A continuous and smooth layer cannot be obtained if the laser power is lower than 1.5kW,while large crystal particles appears in the cladding layer and the corresponding hardness obviously if the laser power is higher than 2.0kW.
The effect of CeO2 on the macro quality,microstructure and micro hardness of Ni/WC cladding layer has been studied.The results indicate that incorporation of CeO2 can greatly refine the microstructure,reduce the crack tendency and improve the micro quality of the Ni/WC cladding layer.The refine effect becomes more evident with increasing CeO2 content.When CeO2 content is increased to 0.16wt%,the micro hardness reaches its maximum of ca.900HV0.3～1300HV0.3 and cracks vanish.Laser power affects the macro quality,microstructure and micro hardness of the cladding layer also.A continuous and smooth layer cannot be obtained if the laser power is lower than 1.5kW,while large crystal particles appears in the cladding layer and the corresponding hardness obviously if the laser power is higher than 2.0kW.
2002, 26(5): 357-358,363.
Abstract:
By using a new method,the characteristic of optical shocks in the presece of dispersion was analyzed;based on the analysis on the critical distance of optical shocks,and the theoretical conclusion that optical shocks can be avoided by one approximate optical soliton were obtained.
By using a new method,the characteristic of optical shocks in the presece of dispersion was analyzed;based on the analysis on the critical distance of optical shocks,and the theoretical conclusion that optical shocks can be avoided by one approximate optical soliton were obtained.
2002, 26(5): 359-363.
Abstract:
This paper investigates laser cladding the sealing surface of high parameter petrochemical valves with 5kW transverse flow CW CO2 laser.The base metal of valves is various,and the cladding powder is CoCrWB or NiCrFeBSi powder.A 2mm～3.5mm thick layer of laser cladding with smooth surface and non flaw can be made,based on solution of crack problem of cladding layer by a single scanning and thick cladding.Various elements and their interaction which influence the formation of crack in laser cladding layer,especially of thick layer,and control of crack are discussed and analyzed according to the experiments.The thought of building a model of stress judgement to judge the formation of crack in cladding layer is put forward.
This paper investigates laser cladding the sealing surface of high parameter petrochemical valves with 5kW transverse flow CW CO2 laser.The base metal of valves is various,and the cladding powder is CoCrWB or NiCrFeBSi powder.A 2mm～3.5mm thick layer of laser cladding with smooth surface and non flaw can be made,based on solution of crack problem of cladding layer by a single scanning and thick cladding.Various elements and their interaction which influence the formation of crack in laser cladding layer,especially of thick layer,and control of crack are discussed and analyzed according to the experiments.The thought of building a model of stress judgement to judge the formation of crack in cladding layer is put forward.
2002, 26(5): 364-366.
Abstract:
Higher order cosh Gaussian beams was defined as a higher-order-cosh function multiplied by a Gaussian function which may be solutions of the paraxial wave equation for propagation in complex optical systems. The beams can be obtained through coherent combinations of decentred Gaussian beams or cosh-Gaussian beams. And the propagation feature of the beams in free space is also investigated. It is found that the intensity distribution may be flattened.
Higher order cosh Gaussian beams was defined as a higher-order-cosh function multiplied by a Gaussian function which may be solutions of the paraxial wave equation for propagation in complex optical systems. The beams can be obtained through coherent combinations of decentred Gaussian beams or cosh-Gaussian beams. And the propagation feature of the beams in free space is also investigated. It is found that the intensity distribution may be flattened.
2002, 26(5): 367-369,372.
Abstract:
The principle of the dispersion managed soliton transmission is introduced.The transmission characteristic of the dispersion managed soliton is analyzed by using numerical simulation.The result shows that the dispersion managed solitons are periodic,and the transmission characteristic is the best in the model that path average dispersion is zero.
The principle of the dispersion managed soliton transmission is introduced.The transmission characteristic of the dispersion managed soliton is analyzed by using numerical simulation.The result shows that the dispersion managed solitons are periodic,and the transmission characteristic is the best in the model that path average dispersion is zero.
2002, 26(5): 370-372.
Abstract:
Based on the fact that circ function can be expanded by an approximate sum of complex Gaussian functions with finite numbers,the analytical formula for the axial intensity distribution of a partially coherent Gaussian Schell model(GSM)beam through a circular lens with finite aperture was derived.The calculation was made and its results were compared to those of the diffracted integral.The result shows that our method can improve the calculation efficiency.
Based on the fact that circ function can be expanded by an approximate sum of complex Gaussian functions with finite numbers,the analytical formula for the axial intensity distribution of a partially coherent Gaussian Schell model(GSM)beam through a circular lens with finite aperture was derived.The calculation was made and its results were compared to those of the diffracted integral.The result shows that our method can improve the calculation efficiency.
2002, 26(5): 373-374,378.
Abstract:
The manufactures all over the world find that it is important to improve the stability of laser welding system for keeping the quality of products.This article studies the stability of the system produced by HG Laser.The result is that this system can be used to weld the sawblade in the range of ∅105mm～∅500mm and the ∅68mm,∅82mm core drill.
The manufactures all over the world find that it is important to improve the stability of laser welding system for keeping the quality of products.This article studies the stability of the system produced by HG Laser.The result is that this system can be used to weld the sawblade in the range of ∅105mm～∅500mm and the ∅68mm,∅82mm core drill.
2002, 26(5): 375-378.
Abstract:
The present research situation and questions of the stimulated Brillouin scattering(SBS) in optical component are summarized in this paper.The ultrasonic wave damage,destroy of the beam quality,and the influence on the high power laser system including many big optical components are emphasized.And the further research direction on this field is pointed out.
The present research situation and questions of the stimulated Brillouin scattering(SBS) in optical component are summarized in this paper.The ultrasonic wave damage,destroy of the beam quality,and the influence on the high power laser system including many big optical components are emphasized.And the further research direction on this field is pointed out.
2002, 26(5): 379-381.
Abstract:
The surface of cylinder bore is treated by the laser honing to form linearly extending lubricant channels and grooves with the predetermined width,depth,angle,shape and gap,which can be well matched to the needs of lubrication.It results in not only remarkably improved property of wear resistance of cylinder and its life span,but also largely decreased HC ejection from the internal combustion engine,the consumption of fuel oil and lubricant,the pollution of catalytic apparatus and the cost of piston.
The surface of cylinder bore is treated by the laser honing to form linearly extending lubricant channels and grooves with the predetermined width,depth,angle,shape and gap,which can be well matched to the needs of lubrication.It results in not only remarkably improved property of wear resistance of cylinder and its life span,but also largely decreased HC ejection from the internal combustion engine,the consumption of fuel oil and lubricant,the pollution of catalytic apparatus and the cost of piston.
2002, 26(5): 382-384,387.
Abstract:
The applications of SBS phase conjugation technology of laser propagation in the atmosphere are reviewed in this paper.The method of realizing the beacon of small area on the target actively with SBS threshold effect in the process of laser propagation in the atmosphere,as well as the close loop process of realizing laser propagation in the atmosphere with SBS phase conjugation are analyzed and its development prospect is introduce.
The applications of SBS phase conjugation technology of laser propagation in the atmosphere are reviewed in this paper.The method of realizing the beacon of small area on the target actively with SBS threshold effect in the process of laser propagation in the atmosphere,as well as the close loop process of realizing laser propagation in the atmosphere with SBS phase conjugation are analyzed and its development prospect is introduce.
2002, 26(5): 385-387.
Abstract:
A kind of fiber Bragg grating(FBG) strain sensor with stainless steel tube jacket is presented in this paper. The sensor has wavelength sensitivity coefficient to strain of 1.19pm/με and excellent linearity was shown between the wavelength shift and the strain. The sensor can be bonded tightly to structure,which makes strain transferred effectively. It is very suitable for measurement of the strain in engineering.
A kind of fiber Bragg grating(FBG) strain sensor with stainless steel tube jacket is presented in this paper. The sensor has wavelength sensitivity coefficient to strain of 1.19pm/με and excellent linearity was shown between the wavelength shift and the strain. The sensor can be bonded tightly to structure,which makes strain transferred effectively. It is very suitable for measurement of the strain in engineering.
2002, 26(5): 388-391.
Abstract:
This paper summarized the research and development on laser direct manufacturing (LDM) metallic components based on laser cladding technology. The various direct manufacturing methods were introduced with the main emphasis on laser clad based manufacturing technology and its important technological constitutes: high quality coaxial nozzle,optimization of the laser cladding technique and the closed loop control of the process. The typical metallic components produced and the main application fields of LDM were demonstrated. The further research interests on LDM were proposed.
This paper summarized the research and development on laser direct manufacturing (LDM) metallic components based on laser cladding technology. The various direct manufacturing methods were introduced with the main emphasis on laser clad based manufacturing technology and its important technological constitutes: high quality coaxial nozzle,optimization of the laser cladding technique and the closed loop control of the process. The typical metallic components produced and the main application fields of LDM were demonstrated. The further research interests on LDM were proposed.
2002, 26(5): 392-393,397.
Abstract:
According to the plasma whose electron density and gain is distributed as parabolid,the propagation and amplification of capillary discharge X-ray within the cylindrical plasma are studied with the geometrical optics approximation by using a simplified model of gain region.Under the parabolic approximation,the relationship between the output intensity and deflection angle as well as the angle and length of refraction are given.
According to the plasma whose electron density and gain is distributed as parabolid,the propagation and amplification of capillary discharge X-ray within the cylindrical plasma are studied with the geometrical optics approximation by using a simplified model of gain region.Under the parabolic approximation,the relationship between the output intensity and deflection angle as well as the angle and length of refraction are given.
2002, 26(5): 394-397.
Abstract:
When a Brillouin-shifted signal interacts with two strong counterpropagating pump beams in a Brillouin active medium,a conjugate field will grow exponentially in time until it depletes the power of the pump beams. This technique can be used to conjugate very weak signals or alternatively a large fraction of the pump power can be transferred into the conjugate beam.
When a Brillouin-shifted signal interacts with two strong counterpropagating pump beams in a Brillouin active medium,a conjugate field will grow exponentially in time until it depletes the power of the pump beams. This technique can be used to conjugate very weak signals or alternatively a large fraction of the pump power can be transferred into the conjugate beam.
2002, 26(5): 398-400.
Abstract:
In this paper,transformation of astigmatic Hermite-cosh-Gaussian beams through an optical symmetrizing system is studied.The influencce of the decentered parameter and the mode index on the symmetrization of Hermite cosh Gaussian beams is discussed.Detailed numerical calculations are performed to illustrate the physical meaning of the symmetrization of astigmatic Hermite-cosh-Gaussian beams.
In this paper,transformation of astigmatic Hermite-cosh-Gaussian beams through an optical symmetrizing system is studied.The influencce of the decentered parameter and the mode index on the symmetrization of Hermite cosh Gaussian beams is discussed.Detailed numerical calculations are performed to illustrate the physical meaning of the symmetrization of astigmatic Hermite-cosh-Gaussian beams.
