To study the influence mechanism of process parameters on the temperature field and the repair performance in Inconel718 nickel-base-superalloy laser additive repairing process, numerical research was carried out. A three-dimensional finite element model was established, and the finite element software ANSYS was used to simulate the temperature field. The influence of the laser power, the scanning speed on the laser additive repairing temperature distribution and the penetration depth and width of the repair zone were analyzed. The numerical result and the experimental measurement result was compared, and the result showed that as the laser power is in the range of 229~668W and the cladding speed is in the range of 6~16mm/s, the metallurgical bond was formed between the repair layer and the matrix material. The maximum temperature at the interface between the repair layer and the substrate is proportional to the laser power and inversely proportional to the scanning speed. The theoretically calculated penetration depth and penetration width of the repair zone are basically consistent with the experimental measurement results. The theoretical simulation can provide theoretical guidance for the parameter optimization in the laser additive repairing process.
Laser shock peening without protective coating leads to mechanical and thermal loads of materials, resulting in surface melting and re-solidification. In this paper, the effect of laser shock peening (LSP) with and without protective coating on the surface behavior of AZ31B magnesium alloy was studied. Study on surface mechanical property of magnesium alloy by different LSP process parameters. The effects of different LSP parameters on the surface properties of the sample were studied by microhardness test, phase analysis, et al. The results show that the increase of laser power density, the surface hardness of the sample increases. Compared with the LSP with protective coating, the LSP without protective coating increases the surface roughness. And resulting microstructure and residual stress state were studied, After LSP treatment, diffraction peaks shift to high angle direction, resulting in residual compressive stress on the surface of the material.
The laser deposition manufacturing (LMD) is a free-form metal deposition process, which allows generating a prototype or small series of near net-shape structures. Despite numerous advantages, one of the most critical issues of the technique is that produced pieces have a deleterious surface finish which requires post machining steps. Mechanical machining method such as milling and grinding has been used to improve the surface quality of the laser additive manufacturing components. However, the mechanical machining method has some drawbacks such as tool wearing and narrow-area difficult to machining. In this paper, we demonstrate the capability of continuous wave (CW) in polishing rough surface of additive manufactured TiAl alloy. The surface morphology, microstructures, corrosion resistance, micro-hardness and wear resistance of samples were characterized using a laser confocal microscopy (OM), scanning electron microscope (SEM), electrochemical analyzer, Vickers hardness machine, and wear tester, respectively. Results revealed that the surface roughness more than 16.06 μm could be reduce to less than 1.76 μm through laser polishing process. It was also found that a hardened layer about 600μm was produced on the TiAl alloy surface after laser finishing. The microhardness of the sample was improved about 8% compared with the mechanical milling method.
With the lightening tendency in the automobile and aircraft industry, the aluminium (Al) alloy and the carbon fiber reinforced thermal polymer (CFRTP) has been widely used. The CFRTP component always needs to be joined with Al alloy to form a CFRTP/Al alloy composite structure. Due to the large differences in the physicochemical properties of CFRTP and Al alloy materials, it is difficult to join with each other. Laser stir welding technology was applied to join CFRTP and Al alloy dissimilar materials in this research. In order to improve the CFRTP/Al alloy joining strength, a surface pre-treating method (laser micro-engraving) was proposed in this paper. Three micro-scale structures were designed and prepared on 7075 Al alloy by surface laser micro-treatment, which are linear grooves, mesh grooves and circular grooves. The morphology and dimensions (width and depth) of the microstructure on the strength of CFRTP / Al alloy joints were studied. The interface morphology and the fracture morphology of the joint were observed by the laser confocal microscopy and the scanning electron microscopy (SEM). Furthermore, the joining mechanism and failure mechanism of the CFRTP/Al alloy joint were explored. The results indicated that the microscale structures play an important role in improving the mechanical properties of Al alloy and CFRTP joins under different laser micro-engraving.
AlCrFeMnNi high-entropy alloy was prepared by laser additive manufacturing with gas-atomized pre-alloy powders. The phase, microstructure and microhardness of HEA have been investigated. The HEAs without electric field controlled and under controlled were composed of single BCC phase. Under the controlling of electric field, the pores presented the phenomenon of reducing. Due to the reducing of pores, the HEA under electric field controlled became harder and exhibited high microhardness of about 529.9 HV0.2, which was 6.49% higher than the HEA without controlled.
Due to the high manufacturing cost of Nickel based alloy compressor blisks, aero engine repairing process research has important engineering significance and economic value. Inconel718 Ni-based superalloy has the advantages of irradiation, corrosion resistance and excellent mechanical and processing properties. In this paper, a production process for the laser additive and subtractive hybrid manufacturing technologies was presented to repair a microcrack of Inconel 718. The whole repairing process includes four steps. Firstly, a pulsed laser was used to clean and etch the crack through materials subtractive. Secondly, a high-power continuous wave laser was used to additive material in the crack by laser deposition. Thirdly, a pulsed laser was applied to remove the excess repair material. Finally, a fiber laser was used to polish surface. The results showed that defect-free repair samples can be obtained with proper processing parameters. Metallurgical bonding could be achieved between the melting Inconel718 powder and the substrate under the action of a high-energy laser beam. The columnar dendrite and inter-dendritic structure in the repair zone are epitaxially grown along the deposition direction. The microstructure in the repair zone was fine and uniform due to the high gradient, high-speed solidification characteristics of the laser rapid fusion. The micro-hardness of the repaired tissue reduced to about 87% of the matrix and there was no new phase produced in the repair zone.
In this paper, the laser cladding method was used to preparation the TiC reinforced Ni-Fe-Al coating on the Ni base superalloy. The Ti/Ni-Fe-Al powder was preset on the Ni base superalloy and the powder layer thickness is 0.5mm. A fiber laser was used the melting Ti/Ni-Fe-Al powder in an inert gas environment. The shape of the cladding layer was tested using laser scanning confocal microscope (LSCM) under different cladding parameters such as the laser power, the melting velocity and the defocused amount. The microstructure, the micro-hardness was tested by LSCM, SEM, Vickers hardness tester. The test result showed that the TiC particles was distributed uniformly in the cladding layer and hardness of the cladding layer was improved from 180HV to 320HV compared with the Ni-Fe-Al cladding layer without TiC powder reinforced, and a metallurgical bonding was produced between the cladding layer and the base metal. The TiC powder could make the Ni-Fe-Al cladding layer grain refining, and the more TiC powder added in the Ni-Fe-Al powder, the smaller grain size was in the cladding layer.
A theoretical model is established to describe the α-RF discharge in slab Oxygen Iodine lasers, according to the
continuity equation of electron density, the electron energy equilibrium equation and the continuity equation of current
density. Assuming a Maxwellian energy distribution, the spatial distributions of electron density and electric field in RF
plasma are obtained by numerical method. The effects of parameters on discharge characteristics have been analyzed.
The results show that the current density has a big effect on the electron density in discharge area. The influences of
excitation frequency on the maximum value of electric field and the thickness of boundary layer are also discussed. And
the spatial distributions of electron energy and excitation efficiency of singlet delta oxygen have been calculated. The
influences of gas mixture on the excitation efficiency of singlet delta oxygen are discussed. It provides references of
parameters for slab discharge in singlet delta oxygen generating.
Cutting brittle materials such as ceramics and glass by lasers or traditional saw method, costly fractures and associated
damage such as chips and cracks can result. In most cases, these problems were caused as a result of the stress was not
controlled properly and exceeded the critical value of the fracture. In this study, a dual-laser-beam method was proposed
to avoid fractures in glass laser cutting, where an off-focused CO2-laser beam was scanning on the top surface of glass
periodically and repeatedly and a preheated-band which has a proper temperature was built. This preheated-band will
reduce the temperature gradients when the glass is cut by the focused CO2-laser beam. Under these conditions, glass can
be cut with melting method without any fractures. The process of cutting glass by dual CO2-laser beams was simulated
numerically with FEA method and the distribution of temperature and thermal stress was investigated. The relationships
between the cutting parameters, such as laser beam diameter, laser power, cutting speed, and the profile of the cutting
groove were also discussed. The result showed that thermal stress decreased with the increasing width of
preheated-banding, and the smaller the diameter of laser beam, the better the quality of the cutting groove was in the
same laser power situation.
A dual laser beams method was proposed to reduce the thermal stresses when machining glass with CO2-laser. A numerical method based on Ansys software was used to simulate temperature and thermal stresses in glass. Thermal stresses in glass with and without CO2-laser preheating have been studied. The results showed that machining glass with dual laser beams could reduce thermal stresses.
A numerical method based on ANSYS software was presented to simulate the temperature and stress distributions on the glass plate under the CO2 laser irradiation. The influences of laser modes and output power on temperature and stress distributions were discussed in this paper, results shown that the TEM00 mode laser is not suitable for preheating glass.
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