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.
TC4 (Ti-6Al-4V) is a comprehensive metal material with excellent ductility, low density, high specific strength, and a series of advantages such as excellent toughness and weldability, so it is widely used in the aerospace industry. Due to defects such as porosity in the welding process and exposure to alternating loads, welded components of titanium alloys in the aerospace industry become the most vulnerable parts and are extremely susceptible to failure and fracture. In this paper, a single-sided sequential laser impact strengthening process is used to treating the laser welds of TC4 titanium alloy cold rolled parts to investigating the tensile properties of the laser welded welds before and after the process. By observing the tensile fracture by SEM, measuring the microhardness by Vickers hardness tester, and measuring the physical phase by XRD diffractometer, the results of these data were combined to analyze the strengthening mechanism of this laser shock peening process on the laser welds of TC4 titanium alloy. The experimental results show that after the surface strengthening process, the tensile strength and surface hardness of TC4 laser welds are improved compared with those before 1the treatment. The analysis shows that the high residual compressive stress layer and grain refinement caused by laser shock peening are the reasons for the improvement of mechanical properties of materials.
Laser surface hardening is one of the effective methods to enhance the mechanical properties of localised surface area of engineering parts made of different types of steels and other metals like ultra-high strength steel etc. Laser surface hardening has many advantages over conventional hardening process like, self-quenching, very fast, control over energy input and localised hardening etc. In order to further improve the surface quality and mechanical properties of 30CrMnSiNi2A ultra-high strength steel parts fabricated by laser deposition manufacturing (LDM). The quenching modified layer was prepared on the surface of 30CrMnSiNi2A steel by laser quenching technology. This work presents the effect of different laser parameters on the surface morphology and mechanical properties of 30CrMnSiNi2A steel after laser hardening. The experimental data of OM morphology, microstructure, micro-hardness and wear property of hardened layer were analyzed by using the methods of range analysis. Effects of these parameters over the micro hardness of the surface are described. It has been found that, there is around 20% increase in hardness after laser hardening. It considerably debased the surface roughness and wear rate of LDM 30CrMnSi2A alloy parts, which has decreased by 53% and 57% than without laser surface hardening parts. Accordingly, industrial applications of laser deposition manufacturing 30CrMnSi2A alloy parts were supposed to be widened by this study.
Ti-6Al-4V (TC4) titanium alloys have been extensively used in aviation due to their good comprehensive mechanical properties. However, TC4 has low hardness and poor wear resistance, which cannot meet the increasingly stringent working environment requirements of aerospace. Thus, it is necessary to enhance their performance by posttreatment. Laser shock peening (LSP) is an advanced surface treatment technology that improve the hardness and fatigue life of the metal material by ultra-high plastic strain. However, laser shock peening has limits to improve the surface hardness of workpiece. And heat treatment can effectively improve the performance of titanium alloys. Therefore, the combination of heat treatment and laser shock peening is used to improve the surface hardness of TC4. In this study, the Ti-6Al-4V (TC4) samples were subjected to one and two LSP impacts, respectively. Heat treatment was performed on the sample that has been subjected to one impact, and one of the heat-treated samples was subjected to one impact again. The surface hardness was measured by a Vickers hardness tester meter. The fracture morphologies were observed by scanning electron microscope (SEM) and phase characterization was measured by X-ray diffractometer (XRD). The effect of laser shock peening and heat treatment on the surface hardness of TC4 samples was experimentally investigated. The results showed that the maximum surface hardness of the treated sample was increased by 56.8% compared with original sample. Therefore, the combination of laser shock peening and heat treatment can greatly increase the surface hardness of the TC4.
Aiming at the problems of tool wear and poor consistency in the mechanical subtraction of Inconel718 nickel-based superalloy complex structural parts in the laser additive and subtractive manufacturing process. In this paper, the short pulse laser is used to perform precision subtractive processing of Inconel 718 superalloy continuous laser deposition manufacturing (LDM) parts. This paper focuses on the research of short pulse laser milling and scanning technology of Inconel718 LDM. Based on the Response Surface Method, the influence of process parameters such as scanning speed, hatch distance and scanning times on the shape accuracy of the inner channel, surface roughness, material removal rate and recast layer was explored. The optimal milling process parameters are obtained as follows: the laser power is 100 W, the scanning speed is 6000 mm / s, the scanning times are 800, and the hatch distance is 0.02 mm.
Carbon Fiber Reinforced 1Plastic (CFRTS) and TC4 titanium alloy have excellent properties such as high stiffness, fatigue resistance and corrosion resistance, which are widely used in aerospace and new energy vehicle manufacturing. Due to the great differences in physical and chemical properties between CFRTS and TC4 titanium alloy, the traditional bonding and riveting methods have the problems of aging and stress concentration. This study introduces the interface composite control process of “picosecond laser cleaning and plastic-covered”. Firstly, CFRTS was subjected to laser cleaning pretreatment to remove the surface epoxy resin. Secondly, laser was used to pretreat the surface microstructure of TC4 titanium alloy. A layer of 0.02 mm PA powder was spread on the surface of the microstructure and melted by laser to form a plastic-covered layer. Finally, the treated CFRTS and TC4 titanium alloys were welded by laser-assisted joining. Compared with the traditional cleaning technology, it was found that the carbon fiber was exposed obviously and the structure was complete on the CFRTS surface after picosecond laser cleaning, and the epoxy resin was removed completely. The porosity of the joint interface is reduced, and the weld morphology is better. The shear strength of CFRTS-TC4 titanium alloy joint is significantly enhanced, and the maximum shear strength is 6333 N.
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.
Laser additive manufacturing (LAM) is a novel technology that uses high-energy laser beam to obtain high performance entities and coatings. However, in this process, it is difficult to control the microstructure of materials effectively by changing the laser parameters. Based on this situation, we proposed a method that using direct electrostatic field (DESF) to assist LAM process. In this paper, we investigated the changes in 316L microstructure after assisted by DESF, and discuss the effect of electrostatic field. Microstructures of the 316L stainless steel sample fabricated by this method were tested. The result showed the solidification direction and grain morphology was influenced by the direction and value of DESF obviously. While the ESF direction is opposite to the laser scanning direction, the grains in the longitudinal-section perform orderly growth and the directions are biased to the laser scanning direction. While the DESF direction is the same as the scanning direction, the original solidification direction is obviously changed and the direction tended to be opposite to the scanning direction.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.