This PDF file contains the front matter associated with SPIE Proceedings Volume 10813 including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

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.

The electronic interconnection based on solution processes using nanomaterials is one of the key technologies in the printed electronics towards flexible and wearable devices in IoT. The laser direct writing of three kinds of conductive micropatterns and the device applications were studied. The first one is a Cu micro-grid structure using a Cu nanoparticle ink and the application to a strain sensor. The second one is a reduced graphene oxide (rGO) interdigitated electrode prepared by laser-induced reduction of graphene oxide (GO) and the application of an rGO/GO/rGO interdigitated microelectrode to a humidity sensor. The third one is a carbon interdigitated electrode prepared by laser carbonization of a polyimide (PI) film and the application to an in-plane micro-supercapacitor (MSC). One of the important features in wearable devices is the stability and reliability under bending conditions. The influences of bending in the electric properties were studied for the Cu micro-grid and an rGO/GO/rGO interdigitated electrode. Remarkable resistance change of the Cu micro-grid structure was observed in bending experiment. An unusual large resistance change was explained by a nanostructure remaining even after sintering. On the other hand, the rGO/GO/rGO structure showed excellent stability of the output signal in humidity sensing experiments against bending. Such a stable electronic properties against bending stress was attributed to the electronic conductivity based on π−π interaction between graphene planes. A crystalline layered structure of graphene planes were clearly observed in TEM images for an rGO film.

The purpose of this paper is to review laser trimming and precision control of alloy strip resistors, which is extensively applied for electronic vehicles and other power electronics. This mini review especially introduces the laser trimming of background, methodology, mechanism, influencing factor and main problem in details. The existing problems and the future development trend of laser trimming are also discussed.

Laser shock processing (LSP) is a novel surface engineering technique that utilizes a nanosecond pulse laser to generate plasma-driven shock waves, which can induce high compressive residual stresses extending to a depth of more than 1 mm from the surface. It has been widely applied to metallic components in aircrafts to improve the fatigue resistance. However, the fundamental mechanisms underlying the effects of LSP on the different materials and their performance remain poorly understood. This manuscript reviews the novel research studies by our team to use experimental approaches to understand the microstructural evolution in metal and ceramic materials during the LSP process, and elucidate the mechanisms that enable LSP to improve mechanical and irradiation properties. In austenitic steels, we discovered that the LSP-induced microstructures could improve the resistance to irradiation damage. The mechanisms are related to the defect sinks generated by LSP such as dislocations and twin boundaries. Compared to metals, LSP has not been widely applied to ceramics and its mechanisms on ceramics are less understood. LSP of alumina ceramics can induce localized plastic deformation near the surface and along grain boundaries. As a result, the mechanical properties of ceramic materials such as fracture toughness can be improved.

Around BIVOJ laser system, a new generation diode pump solid state laser (10-100J energy in 2-10 ns pulses with 10 Hz repetition frequency at 1030 nm) recently was developed a LSP experimental station. In this paper status and further developments of LSP facility at HiLASE Centre as well as further BIVOJ laser upgrades are presented. Residual stress curves representing preliminary results on treating Aluminum 7075 alloy will be also reported.

Laser aided additive manufacturing (LAAM) was used to prepare FeCrNiMnCo high entropy alloy (HEA) with pre-alloyed powders. The microstructure and properties of the HEA were investigated intensively, especially the cryogenic mechanical properties. The microstructure of the as deposited specimen was dense and occupied by cellular and dendrite grains. The tensile strength and yield strength increased with temperature decreasing from 25°C to -130 °C, yet the impact toughness decreased. The deformation mechanism of the HEA under low temperature was discussed accordingly.

A 3D transient finite element model of Inconel 718 nickel-based superalloy processed by selective laser melting was developed to study the heat flux in the molten pool under the condition of different process parameters and its effect on the temperature field and the shape of molten pool, in which a solid heat transfer module and a laminar flow module in the finite element simulation software COMSOL Multiphysics was applied. In the simulation several special phenomenon characterized with SLM process was considered, such as the interaction between the laser and material with stochastic porosity distribution on powder bed, and the nonlinear change of thermophysical properties due to the state change of material and the influence of the Marangoni effect in the molten pool. The results show that the Marangoni effect caused by the surface tension of molten pool makes the convective heat flux play a leading role in the heat transfer process in the molten pool, and its depth/width ratio is changed by changing the magnitude and direction of the heat flow, what determines the shape of molten pool. The increase in laser power or reduced scanning speed can increase the heat input per unit time, and then lead to a Marangoni convection enhancement within the molten pool, thus enlarge the size of the molten pool. The experimental results are in good agreement with the simulation results.

In the paper, the effects of porosities and average particle sizes of powder layer on light absorption during SLM process were investigated, in which closed-packing models based on Horsfieled’s filling method were established and light absorption was simulated using ray tracing based on laser-material interaction mechanism. The results show the absorption of powder layer of Ti6Al4V alloy is higher than 70%. The decrease of porosity of powder layer benefits to improve the absorption, while the absorption tends to decrease if porosity decreases to a certain value due to the reflection. The decrease of average particle size of powder particles benefits also to improve the absorption. If the light irradiates at positions with different particle arrangements, the absorption behavior changes with irradiation condition whether there occurs the multi-reflection. The above research provides theoretical basis for preparation of new powder materials, their parameter developing for SLM technology and even the properties regulation of SLM fabricated component.

Superhydrophobic surfaces with various levels of adhesion have attracted tremendous research attentions due to their potential applications in both academic research and industrial application. Herein, we proposed a rapid and simple method to realize superhydrophobic surfaces with tunable water adhesion by nanosecond pulse laser irradiation on PTFE. The surfaces were composed of nanoscale and microscale square array. By only adjusting the power of the laser scanning, the adhesive forces between the water droplets and the as-prepared PTFE surfaces could be dynamically tuned. The tunable water adhesion was mainly ascribed to the change of micro/nano structure on the as-prepared surfaces which resulted from the change laser power. The as-prepared superhydrophobic surfaces showed tunable water adhesion from ultralow to ultrahigh, on which the static contact angle (SCA) of up to 155.2 ± 1.5°, and the sliding angle (CA) can be controlled from 3 ± 0.5° to > 90°. The tunable adhesive surperhydrophobic surfaces could be achieved by a fast laser scanning speed. Compared with the other laser equipment, the 355nm nanosecond pulse laser had a high single photon energy, high processing speed, low equipment cost and maintenance cost, and showed a huge potential in industrial applications for large-scale fabrication of superhydrophobic surfaces.

With the development of nanotechnology, nanomaterial have been widely used in many fields, such as medical technology, catalysis, and biotechnology. Among the methods of nanomaterial fabrication, pulsed laser ablation in liquids (LAL) has attracted great attention as a green and versatile approach to fabricate manifold nanomaterial with ligand-free surface. LAL physical process and mechanism is complicated. Firstly laser focus on the target material through the liquid layer, and the surface material is exfoliated. Then the plasma is generated and expands, accompanying the plasma shock wave. Afterwards, the plasma quenches and releases energy into the surrounding liquid. Finally cavitation bubble appears and collapses. These complex mechanisms affect the properties of the prepared nanomaterial, including shape, size, structure, photoelectric properties, etc. Here, we investigate physical process and mechanism of nanomaterial prepared by LAL in detail using high-speed camera experimental system and CFD (Computational Fluid Dynamics) simulation mode. According to the analysis of LAL mechanism, it is reasonable to assume that laser-induced bubble can act as an ideal reactor for nanomaterial synthesis. The movement of the nanoparticles depends on the bubble oscillation. They move outward when the bubble expands and move inward when the bubble shrinks. It shows that the velocity, pressure and the temperature are high at the beginning of expansion and the collapse moment of the bubble, which is quiet benefited for the nanomaterial synthesis.

Laser cladding (LC), with small heat affected zone (HAZ) and lower dilution, is a promising way to repair and strengthen the rail. However, the traditional LC may lead to the cracking of the coatings and the martensitic transformation in the HAZ; which will threaten the safety of railway transportation. In this work, laser-induction hybrid cladding (LIHC) was innovatively proposed to prepare Ni-based coatings on a fullscale rail. Cracking behaviors, microstructures and mechanical properties of the coatings obtained by LC and LIHC were studied systemically. The results indicate that the cracks appeared in the HAZ of the specimen prepared by LC can be prevented LIHC, and the coatings obtained exhibit higher second dendrite arm spacing (SDAS). However, the martensitic structures with high hardness of HV730-HV900 in the HAZ by LC could not be avoided by LIHC, while the HAZ has lower plasticity and fracture toughness, which may accelerate the extending rate of cracks.