Selection Of Laser Processing Parameters Research Articles

Plastic deformation behavior and strengthening mechanism of SLM 316L reinforced by micro-TiC particles

In this work, the integrated study on the microstructure evolution, plastic deformation behavior, and strengthening mechanism of Selective Laser Melting (SLM) 316L austenitic stainless steel (ASS) reinforced with micro-TiC particles was investigated. The results indicated that there were lots of small angle grain boundaries in SLM 316L ASS, and the high dislocation density and component segregation of the cellular dislocation structure resulted in a good combination of high strength and good elongation in performance. The tensile strength, yield strength, and elongation of SLM 316L ASS were 682 MPa, 571 MPa, and 49.9%, respectively. The addition of TiC reinforced particles induced microstructure evolution, including grain refinement, reduction of epitaxial columnar dendrites, reduction of low angle grain boundary (LAGB) ratio and increase of Σ3 (60°/<111>) twin boundaries. Through the effects of grain refinement strengthening, Orowan strengthening, and dislocation strengthening, SLM 316L-2TiC showed a higher tensile strength of 1021 MPa and higher yield strength of 809 MPa, while maintaining an elongation of 30.8% due to the suppression of plasticity by twinning induced plasticity (TWIP) effect. Although nano-reinforced particles were commonly used to improve mechanical properties, in our work, we chose to add micrometer-sized TiC particles, and the strength of the SLM 316L-2TiC metallic matrix composites (MMCs) exceeded the previous reports of adding nanoparticles. The reason was that the small contact angle between TiC and 316L provides good wettability between the particles and the melt, and the selection of laser processing parameters ensures good bonding between TiC particles and the substrate.

Selection of laser processing parameters for hot stamping tools based on mathematical planning of the experiment

The results of experimental studies to determine the influence of the technological parameters of laser processing of 3Kh3M3F die steel on the service life of the working tool of a hot-stamping machine designed for hot stamping of rolling bearing rings are presented. Development of a mathematical model of the tool's resistance to laser radiation parameters was carried out by the method of mathematical planning of the experiment using a full factorial experiment. Durability of the die tool N (in thousand forgings) was chosen as an optimization criterion, while dimensionless (generalized) parameters of the speed V* and power P* of laser processing, as well as the overlap coefficient of laser tracks S* were proposed to use as factors. The obtained mathematical model of the resistance of laser-hardened die tools for hot deformation is used for the development and optimization of laser quenching modes without melting the surface of the ejectors in order to increase their thermal fatigue strength. Due to the fact that dimensionless factors containing the thermophysical characteristics of the die tool material are used in the planning of the experiment, the developed mathematical model can be used to assess the operational resistance of other heat-resistant tool steels of the martensite class.

Surface characterization of laser-induced molten area in micro-grooving of silicon by ultraviolet (UV) laser

The objective of this research is to understand the fundamental mechanisms that govern the formation of laser-induced molten area during the micro-grooved fabrication on silicon material. In this research work, micro grooves were fabricated on silicon wafer by using ultraviolet (UV) laser of 248nm wavelength. Influence of lasing parameters such as pulse duration, laser pulse energy and scanning speed on the surface of micro-grooved was characterized. It is found that, the width of the micro grooves become wider with increasing laser pulse energy when ultraviolet laser was irradiated on silicon material. On the other hand, heat affected zone (HAZ) can be found at the surface of micro groove line at high pulse energy, high pulse repetition rate and lower scanning speed irradiation condition. This is considered due to the excessive heat input of the laser irradiation condition. It is concluded that proper selection of laser processing parameters of pulse energy, E, pulse repetition rate, R p , and scanning speed is necessary to achieve high quality micro-grooves.

Laser Processing of Multilayered Thermal Spray Coatings: Optimal Processing Parameters

Laser processing offers an innovative approach for the fabrication and transformation of a wide range of materials. As a rapid, non-contact, and precision material removal technology, lasers are natural tools to process thermal spray coatings. Recently, a thermoelectric generator (TEG) was fabricated using thermal spray and laser processing. The TEG device represents a multilayer, multimaterial functional thermal spray structure, with laser processing serving an essential role in its fabrication. Several unique challenges are presented when processing such multilayer coatings, and the focus of this work is on the selection of laser processing parameters for optimal feature quality and device performance. A parametric study is carried out using three short-pulse lasers, where laser power, repetition rate and processing speed are varied to determine the laser parameters that result in high-quality features. The resulting laser patterns are characterized using optical and scanning electron microscopy, energy-dispersive x-ray spectroscopy, and electrical isolation tests between patterned regions. The underlying laser interaction and material removal mechanisms that affect the feature quality are discussed. Feature quality was found to improve both by using a multiscanning approach and an optional assist gas of air or nitrogen. Electrically isolated regions were also patterned in a cylindrical test specimen.

Solution-Processed Organic Thin-Film Transistor Arrays with the Assistance of Laser Ablation

A key step toward commercialization of organic thin-film transistors (OTFTs) is to manufacture large-area OTFT arrays with desired uniform device performance. In this work, for the first time, solution-processed OTFT arrays were fabricated with the assistance of laser ablation. The source-drain electrodes and the whole devices were patterned by precise control of laser intensity and process path. Compared with traditional methods, this approach significantly simplifies the fabrication process of OTFT arrays with high quality and high yield. A careful selection of laser processing parameters is key to obtaining high quality and high performance OTFT arrays. The grazing incidence X-ray diffraction experiments and device performance tests ensured the selection of proper laser ablation intensity. Eventually, the OTFT arrays on silicon wafer and ITO glass exhibited uniform electrical characteristics with the mean mobility of 0.16 and 0.10 cm2 V-1 s-1, respectively. These results demonstrated that the laser ablation process provides a promising tool to simplify the fabrication of solution-processed OTFT arrays with low cost and high yield, which has great potential in upscaling of high performance OTFT arrays for display and circuits.

Ablation and morphological evolution of micro-holes in stainless steel with picosecond laser pulses

An experimental study is presented of micro-hole drilling on the surface of stainless steel using a 10-ps Q-switched Nd:VAN pulsed laser at two wavelengths, 532 and 1064 nm, with multiple powers and different number of pulses. Results show that two primary ablation mechanisms for ultrashort laser machining, i.e., vaporization and phase explosion, which correspond to gentle and strong ablations, are correlated mainly with the applied laser power. From measured data, two ablation thresholds are calculated using a piece-wise linear fitting. Moreover, surface recast layer associated with strong ablation can be eliminated by an appropriate selection of laser processing parameters. The Hirschegg model is applied to analyze the evolution of hole depth as a function of laser processing parameters for the two wavelengths. For the 532-nm wavelength laser ablation, the shapes and morphology of micro-holes evolve differently with low power from high power. In addition, the related reasons inducing multiple featured hole shapes are discussed.

Evolution of surface topography in one-dimensional laser machining of structural alumina

High energy lasers are an emerging industrial tool to fabricate complex shapes on hard and brittle structural ceramics such as alumina. The selection of laser processing parameters and the prediction of material removal rates during the laser machining are the critical issues. This paper was attempted to present the state of the art of laser machining of alumina using an integrated experimental and computational approach. A multistep computational model based on COMSOL™ Multiphysics was developed to study the influence of various single-pulse laser energy densities and associated physical phenomena (recoil pressure, Marangoni convection, and surface tension) on the temperature history, fluid velocity, crater size, and surface topography. A pulsed Nd:YAG laser was employed to machine alumina under different processing conditions. The surface topography of laser machined alumina was measured by an optical profilometer and the results were compared with the computationally predicted topographic parameters with reasonably close agreement.