Effects Of Laser Processing Parameters Research Articles

Effect of Laser Parameters on Fracture Properties of Laser-Repaired Cracks with Micro/NanoMaterial Addition: Multiscale Analysis.

In laser crack repair processes, laser parameters have significant influence on repair quality. Improper combination of laser process parameters may result in defects-such as porosity, ablation, and coarse grain size-in remelted zones. A trans-scale computational model is established by combining crystal plasticity finite elements and variable-node finite elements. The influence of microstructure characteristics such as grain size and porosity of the repair layer on the cumulative plastic slip (CPS) on the dominant slip system at the meso-scale and the J-integral at the macro-scale is studied to explore the effect of laser process parameters on repair quality. The results show that when the laser power is 1800 W and the heating time is 0.5 s, the grain size and porosity of the repaired specimen are the smallest. The J-integral of the repaired specimen is more than 8% smaller than that of the unrepaired specimen and about 3% smaller than that of the repaired specimen, with a laser power of 2000 W and a heating time of 1 s. Pores increase the CPS of the crystal around the pores, especially when a pore have sharp corners. Selecting appropriate laser process parameters can not only refine grain size but also reduce the volume fraction of pores and thus reduce the J-integral and eventually improve repair quality of repaired specimens. The study investigates the relationship of process parameter-microstructure-repair quality in the laser repair process and provides a method for studying the mechanical behavior of materials at macro and micro scales.

Characterization of TiC particle reinforced magnesium matrix composites (MMCs) prepared by laser cladding based on element evaporation

In this study, we report the preparation of AZ31/TiC composites by laser cladding based on elemental vaporization and supplementation and investigate the effects of laser process parameters and mixed powder ratio on the vaporization and spattering. It was found that the capillary pressure generated by using TiC could effectively suppress the molten pool sputtering during laser cladding. In addition, TiC particles promoted the recrystallisation behavior of the molten pool, and the grains were significantly refined from 61.58 μm to 6.46 μm. The random orientation of the recrystallized grains led to a weaker texture, decrease from 12.349 to 1.964. The microhardness of the composites higher than AZ31 from 46 to 86.2 HV0.2, and the average wear rate was reduced by 21.9%.

Preparation and Wettability Analysis of Metal Biofunctional Surfaces Based on the Microquadrangular Structure.

Improving the hydrophobic properties of aluminum alloys is crucial for industry. In previous reports, researchers prepared superhydrophobic surfaces by fabricating micro-nanostructures on the metal surface with a nanosecond laser. However, no researchers have formed microquadrangular groove structures on the metal surface. In this article, inspired by the bamboo leaf, a microquadrangular structure is designed and processed using nanosecond laser technology to form a superhydrophobic functional surface. The effects of laser processing parameters, such as laser power, scanning speed, scanning time, defocus and fill spacing on the size, surface morphology features, and wettability of the microquadrangular structure, are investigated by a single-factor experimental method. The experimental results show the optimal size of the processed microquadrangular structure obtained from the experiment with an error of 1.28% from the design size, where the fill spacing has the greatest effect on the size and the scanning time, defocus, and fill spacing have great influence on the surface morphology. The contact angle of water drops on the surface can reach 154.7°, and the power has the greatest influence on the wettability. Laser parameters have distinct effects on the properties of the materials. Therefore, by regulation of the laser parameters, the formation of the microstructure can be availably controlled and the result of hydrophobicity can be achieved.

Model-Based Sensitivity Analysis of the Temperature in Laser Powder Bed Fusion.

To quantitatively evaluate the effect of the process parameters and the material properties on the temperature in laser powder bed fusion (LPBF), this paper proposed a sensitivity analysis of the temperature based on the validated prediction model. First, three different heat source modes-point heat source, Gaussian surface heat source, and Gaussian body heat source-were introduced. Then, a case study of Ti6Al4V is conducted to determine the suitable range of heat source density for the three different heat source models. Based on this, the effects of laser processing parameters and material thermophysical parameters on the temperature field and molten pool size are quantitatively discussed based on the Gaussian surface heat source. The results indicate that the Gaussian surface heat source and the Gaussian body heat source offer higher prediction accuracy for molten pool width compared to the point heat source under similar processing parameters. When the laser energy density is between 40 and 70 J/mm3, the prediction accuracy of the Gaussian surface heat source and the body heat source is similar, and the average prediction errors are 4.427% and 2.613%, respectively. When the laser energy density is between 70 and 90 J/mm3, the prediction accuracy of the Gaussian body heat source is superior to that of the Gaussian surface heat source. Among the influencing factors, laser power exerts the greatest influence on the temperature field and molten pool size, followed by scanning speed. In particular, laser power and scan speed contribute 38.9% and 23.5% to the width of the molten pool, 39.1% and 19.6% to the depth of the molten pool, and 38.9% and 21.5% to the maximum temperature, respectively.

The internal modified layer structure of silicon carbide induced by ultrafast laser and its application in stealth dicing

Silicon carbide (SiC) is widely applied in high-power electronic devices due to its excellent properties. Stealth dicing (SD) as one of the dicing methods, exhibits the advantages of few thermal surface damage and low edge-chipping. In this study, we use an ultrafast laser to induce the modified layer structure inside the SiC wafers. The effects of laser processing parameters on the modified layers are studied. The formation mechanism of the modified layer and its influence on SD are analyzed. The result shows that the number of modified layer structures is mainly determined by the moving velocity. The different modified layer structures will affect the surface roughness of the SD cross-section and critical fracture load of the 4H–SiC wafers. Finally, we achieved the high-quality SD of SiC wafers, and a cross-section with the minimum surface roughness is approximately 381 nm.

Surface Integrity in Laser De-coating of Tooling

Laser de-coating technology is a promising method for the selective removal of coatings on cutting tools. When the coating is removed, it is essential to ensure that the surface integrity is not compromised. The laser cleaning process can also be targeted to enhance surface integrity. Among the many different types of coating used on tooling is Diamond-like Carbon (DLC). The coating has excellent performance in terms of a low coefficient of friction. This research investigates the effect of laser de-coating on the surface morphology, composition, residual stress, nano hardness, and surface roughness when removing DLC coating on tungsten carbide substrates to facilitate re-use in a circular economy. The research provides a greater understanding of the effect of laser process parameters in de-coating and on preserving the surface integrity and enabling favorable residual stress. This research is vital in the transition towards optimized remanufacturing of tooling and in enabling circularity.

High Power Laser Cutting of SiC-Al2O3 Ceramic Matrix Composites

Machining composite to achieve the desired surface and sub-surface condition, whether through conventional or non-conventional techniques, presents persistent challenges due to their anisotropic thermal characteristics. These challenges escalate when dealing with ceramic matrix composites (CMC) due to their high melting and boiling temperature. This study investigates the surface and sub-surface characteristics of SiC-Al2O3 CMC laser-cut components, produced using a 2 kW quasi-continuous wave laser. The influence of laser parameters such as focal position, cutting speed, number of cutting passes, average power, and assist gas type on surface and sub-surface characteristics have been investigated in detail. The laser cut samples were analysed using white light interferometer, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and 3D X-ray Computer Tomography (XCT) for both surface and sub-surface characteristics. The effect of laser process parameters on the surface composition, surface topology, and sub-surface thermal defects have been studied in detail. The results revealed that multi-pass cutting (16 pass) can be used to achieve lower thermal affected zone (~200 µm) and reduced surface roughness with an overall cutting speed of 625 mm/min. No delamination was observed with multi-pass cutting. Nitrogen was found to be the most suitable assist gas, as it prevented oxide layer formation across the laser cut SiC-Al2O3 CMC surface.

Fabrication of super hydrophilic surface on FeCrAl-WM with ridged microstructure for Joule-heating catalyst support by UV-laser microprocessing

The catalyst support with super hydrophilic surface facilitates uniform loading and firm adhesion of the catalyst. In this paper, ridged microstructures were fabricated on the surface of FeCrAl wire mesh (FeCrAl-WM) by UV-laser processing. The mechanism behind the formation of ridged microstructures was elucidated. The influence of scanning interval on the stacking and separation of recast layers was analyzed. The effects of laser processing parameters on surface roughness and hydrophilicity of FeCrAl-WM surface with ridged microstructures were investigated. By adjusting laser processing parameters, it is possible to regulate both the roughness factor and oxygen content of the FeCrAl-WM surface, thereby controlling its hydrophilicity and varying contact angles between 0° and 90°. Catalyst loading experiments were conducted on FeCrAl-WM after laser processing, followed by testing the performance of MSR microreactor for hydrogen production using FeCrAl-WM as a catalyst support material. At an inlet flow rate of 4 ml/h at 280 °C, a maximum hydrogen production rate of 0.21 mol/h was achieved with a methanol conversion rate reaching 91.5 %. We envision that the laser microprocessing offers a convenient and effective approach to develop super hydrophilic surface on FeCrAl-WM materials for use as Joule-heating catalyst support.

Theoretical investigations of population trapping phenomena in atomic four-color, three-step photoionization scheme

The four-color three-step selective photoionization process of atom is very important in laser isotope separation technology. The population trapping phenomena and their influences are studied theoretically in monochromatic and non-monochromatic laser fields based on the density matrix theory in this work. Time evolutions of the photoionization properties of the four-color, three-step process are given. The population trapping effects occur intensely in monochromatic excitation, while it gradually turns weak as the laser bandwidth increases. The effects of bandwidth, Rabi frequency, time delay, and frequency detuning on the population trapping effect are investigated in monochromatic and non-monochromatic laser fields. The effects of laser process parameters and atomic parameters on the effective selective photoionization are also discussed. The ionization probability and selectivity factors, as evaluation indexes, are difficult to improve synchronously by adjusting systematic parameters. Besides, the existence of metastable state may play a negative role when its population is low enough.

Direct Laser Interference Patterning of Zirconia Using Infra‐Red Picosecond Pulsed Laser: Effect of Laser Processing Parameters on the Surface Topography and Microstructure

AbstractThis study investigates the influence of processing parameters when applying direct laser interference patterning (DLIP) on the morphology and microstructure of zirconia surfaces using a 10 ps‐pulsed laser source with 1064 nm wavelength. An experimental testing matrix is built with different values of laser fluence (5.7–18.2 J cm−2) and pulse overlap (66–98%). Surface morphology and microstructure are characterized by confocal microscopy and scanning electron microscopy. Homogeneous line‐like patterns with periodic spatial repetition of 5.0 µm, with varying depths, widths, and aspect ratio, are fabricated using proper processing parameters (5.7–7.6 J cm−2 and 92–96%). Structures with maximum depth of 1.5 µm and sharp edges are obtained (7.6 J cm−2 and 96% overlap). Ablated regions presented a morphology typical of photophysical ablation mechanism, with signs of molten material at the surface. Sub‐micrometric pores and nanodroplets are registered for all conditions, while sub‐micrometric cracks developed only for higher fluences. A processing window conducing to homogenous DLIP structures is set based on experimental data. Periodic structures with multiscale topographic features are successfully obtained on zirconia surfaces using DLIP technology in this study. These outcomes open new perspectives for fabrication of multifunctional zirconia surfaces for advanced biomedical and engineering applications.

Effect of laser process parameters on contact angle for linear and square grid micro-textured surfaces

Bio-mimicking of self-cleaning surfaces is presently being regarded as a promising area of research, especially in bio-implants. Self-cleaning properties of surfaces are mostly evaluated on the basis of contact angle attained by fluids with the contact surfaces. Micro/nano-textured patterns on the surfaces govern the surface tension of liquid thereby contact angle. Accordingly, the hydrophobic and/or hydrophilic nature of surfaces is anticipated according to the application requirements. This work presents comparative evaluation of self-cleaning performance of linear and square grid micro-textured surfaces. The micro-textures were fabricated on biocompatible Ti-6Al-4V alloy substrate using nanosecond pulsed laser. The effect of laser power, scan speed and frequency on contact angle has been investigated. Laser power of 7–14 watts, scan speed of 300–375 mm/s and frequency of 50–80 kHz were laser process parameters for study. Taguchi approach of experimentation followed by ANOVA was adopted for experimentation and analysis. A very precise and accurate contact angle goniometer setup was developed, tested and calibrated inhouse using image analysis software for contact angle measurements. Laser power and frequency were the significant factors deciding hydrophobicity. Surface morphology has also been studied to resemble and realize the extent of lotus leaf effect achieved. Square grid micro-textures exhibited better contact angle compared to linear micro-textures.

Experimental investigation of nanosecond laser Machining of 3D printed carbon fiber reinforced polymer (CFRP) composite

Carbon fiber reinforced polymer (CFRP) composites are widely used in automotive and aerospace applications due to their high specific strengths, high fatigue and creep resistance, and excellent corrosion resistance. Additive manufacturing (AM) or 3D printing has opened new ways of manufacturing complex 3D parts using CFRP composites. As a result, researchers have gained interest in the machining or post-processing of 3D-printed CFRP composites. This study aims to investigate the feasibility of using a nanosecond laser for machining single craters or blind holes and slots on 3D printed CFRP samples and understand the effects of important process parameters on feature dimensions, (i.e., crater diameter, slot width, crater/hole depth, and slot depth), heat affected zone (HAZ), and surface quality of the machined features. A 1064 nm wavelength laser system with a focal length of 160 mm was used, whereas the number of pulses, laser energy level, and back-and-forth laser passes are varied. The heat-affected zone is found to be influenced by the laser energy level as compared to the number of pulses. It is found that for the same number of pulses, there is a clear sign of an increase in HAZ with the increase in laser energy level. With the increase in the number of pulses, the hole or slot edge becomes more defined and clearer, whereas the HAZ is mostly determined by the energy level. There is an accumulation of molten or removed materials at the edge of holes or slots causing jagged edges of machined features, which gradually diminishes when the edge becomes smoother for a higher number of pulses, or accumulated materials evaporate away at the higher setting of energy level. Finally, it is found that the nanosecond laser system is capable of machining quality holes and slots on the 3D-printed CFRP composite. To obtain features with well-defined profiles and minimal heat-affected zone, an understanding of the effects of laser process parameters is important.

Selective laser melting of oxide dispersion strengthened MA956 alloy and its surface finishing by magnetic field assisted finishing

Selective laser melting (SLM) is a prominent metal additive manufacturing (AM) capable of processing a myriad of engineering materials with high precision and design freedom. However, similar to other AM processes, poor surface finishing has been an omnipresent problem in SLM technology. In this study, magnetic field assisted finishing (MAF) was used to finish SLM fabricated oxide dispersion strengthened (ODS) MA956, an iron‑chromium‑aluminum alloy. The effect of laser processing parameters on part density and surface roughness was first studied. Using a multi-objective optimization technique, the optimal parameters to obtain the highest density and lowest surface roughness were determined. Finally, MAF was applied to the parts built with the obtained optimal SLM parameters, but without significant improvement on the surfaces of as-printed samples. Hence, the surfaces of as-printed samples were post-processed (ground) to yield better initial surface conditions prior to MAF. The effect of initial roughness, iron particles size, and abrasive size on MAF performance was studied. Initial roughness had the most dominant effect followed by abrasive size. The underlying mechanism behind the dependency on initial roughness on final surface quality was analyzed by studying the change on the surface profiles with different starting initial roughness. The initial roughness required for MAF to be effective was determined. Using the optimal processing conditions, MAF was applied to the post-processed samples to attain the final average surface roughness (Ra) as little as 0.36 μm starting from initial average roughness (Ra) of 1.53 μm.

Study on Macromorphology and Microstructure of Laser Cladding NiCrBSi Alloy Cladding Layer

Laser cladding technology is an advanced surface modification technology that can achieve the coating, repair, and manufacturing of surfaces of metals, alloys, ceramics, and other materials. Laser cladding technology has the advantages of high efficiency, high accuracy, and the ability to achieve multi material composites, and is widely used in automotive, aerospace, shipbuilding, medical and other fields. However, there are also some problems with laser cladding technology, such as unstable weld pool morphology, uneven weld pool depth, and thermal stress, which limit its application range and the need to improve efficiency. Therefore, how to further improve the efficiency and quality of laser cladding technology has been an important research direction for researchers. Through nine orthogonal experiments without electromagnetic field, the effects of laser processing parameters, such as laser power, spot diameter, and scanning speed, on the quality of the cladding layer were studied. For melting height, scanning speed is the most significant influencing factor; For the melt width, the spot diameter is the most significant influencing factor; For the penetration depth, the laser power is the most significant factor. Through comprehensive comparison of subsequent morphology observation and mechanical property testing, it is concluded that laser power of 1500W, spot diameter of 3mm, and scanning speed of 4mm/s are the best process parameters, providing guidance for subsequent cladding experiments.

A study on geometrical aspects in laser cladding by lateral powder injection technique

Laser cladding is carried out using lateral powder feeding method and the effect of direction of deposition on the clad track geometry is studied. Further, the effect of laser process parameters i.e., laser power and scan speed on the forming characteristics of clad track are also studied. The lateral nozzle with 1 mm diameter feed powder (Inconel 718) with 60° angle to the substrate (Stain Steel-AISI 304). With the different direction of scanning with different laser process parameter, mass flow and carrier gas (Argon) pressure the scanning direction opposite to power flow (+Y) formed uniform clad bed with height, width, and minimum dilution. At higher rate of carrier gas flow the molten poll is well-shielded and preventing oxidation. In addition, 2D thin wall formed, also hardness (360 Hv0.05) of the wall uniform throughout and no porosity throughout the wall.

Ultraviolet Nanosecond Laser-Ablated Groove Analysis of 2.5D Cf/SiC Composites

The 2.5D Cf/SiC composite is a typical heterogeneous material with the characteristics of anisotropy, which makes it difficult to predict the size and damage removed by the traditional contact removal process. This paper adopted the ultraviolet nanosecond laser to ablate the Cf/SiC composites by considering the heterogeneous structure’s effect. The ablated groove topography and size prediction are effective in revealing the machined quality with predictable groove sizes. The effects of laser processing parameters on the groove morphology and surface thermally affected zone are investigated with the thermal removal mechanism. A regression model is established by considering the scanning times, scanning speed, laser power and pulse width as the main variables. In the regression models, the relative error values are all below 10%. It is revealed that the groove width diminishes with the scanning speed and increases as the laser power increases. However, the influence of the scanning times and pulse width is small, and the overall variation range is within ±10 μm. The results show that the arrangement direction of carbon fibers has an impact on laser processing, especially when the pulse width is 0.25 μs, upon which the opposite change occurs. Carbon fiber grooves are not obvious and are barely observed in the laser processing of the parallel carbon fiber direction, and the grooves are slightly uneven. This study could be helpful in analyzing the grooves of Cf/SiC affected by the laser processing process, which could support the hybrid machining of the Cf/SiC composites.

Surface Microprocessing AISI-O1 by Pulsed Nd: YAG Laser

Due to tedious and time-consuming work put into the conventional mold/die microprocessing (about 37% of the total time of the entire mold/die production). Therefore, to improve or enhance the quality of mold/dies at the final step with a less number of trained and skilled operators or decrease the processing time to cut the overall cost dramatically, AISI-O1 cold work steel was micro-processed by Pulsed Nd: YAG laser. The influence of laser processing parameters on the evolution of the correlated surface morphology was investigated by a 3D profilometer, scanning electron microscopy (SEM), and optical microscopy (OM). The results show that when AISI-O1 specimens were irradiated with various parameters, the morphology of AISI-O1 cold work steel was changed correspondingly. It also demonstrates that the different kinds of micro-processed surface morphology could be established successfully to satisfy the later practical requirements for a given laser. Meanwhile, the effect of laser processing parameters on the relevant temperature was described, and the laser microprocessing temperature field was also proposed. It reveals that the influence of laser pulse feed rate was more prominent than that of other parameters on the relevant micro-processed surface morphology.

Internal modified structure of silicon carbide prepared by ultrafast laser for wafer slicing

Silicon Carbide (SiC) is an important substrate material for electronic components due to its excellent properties. Compared with wire sawing technology, laser slicing technology is a promising method that can achieve the slicing of SiC wafers without kerf-loss. In this paper, the modified layer for SiC slicing was obtained by ultrafast laser processing inside semi-insulating SiC wafers. We studied the effect of pulse duration on the internal modification process and discussed the formation mechanism of the modified layer according to morphology and composition. The effect of laser processing parameters on the morphology of the modified layer was systematically studied as well as tensile tests were carried out on samples with different morphologies of the modified layer, which revealed the effect of the modified layer on the peeling. The results show that the increase in pulse duration favors the formation of internal modified structures, which are mainly composed of amorphous Si, amorphous C, amorphous SiC and SiC crystals. The change of process parameters will affect the type of structure and the formation of cracks in the modified layer. Only the sample with a single-crack layer was exfoliated successfully, proving that the crack morphology has an essential influence on the peeling.

Correction to: Effects of laser process parameters on the hardness profile of AISI 4340 cylindrical samples: statistical and experimental analyses

Correction to: Effects of laser process parameters on the hardness profile of AISI 4340 cylindrical samples: statistical and experimental analyses

Large-area regular periodic surface structures on 4H-SiC induced by defocused femtosecond laser

Femtosecond (fs) laser has been proved to induce periodic surface structure formation with various periods. Previous studies employed complex optical means and specific processing environments to induce nano-sized periodic surface structures. In this study, a defocused fs laser was utilized to realize a high-stability and straightforward method for generating periodic structures on silicon carbide (SiC) surfaces. Due to its more uniform energy distribution, the defocused laser effectively attenuates the unstable fluid flow caused by the Marangoni convection, thereby improving the consistency of laser- induced periodic surface structure morphology and size. The effects of laser processing parameters on the ripple period, density, and morphology were systematically investigated. Moreover, an appropriate physical process was adopted to explain the formation of the nanostructures. A high laser pulse number was considered the key to forming large-area dense nanoripples, which possessed a smooth edge profile and similar period. Under optimal parameters, large-area regular nanoripples with periods of ∼100 nm could be induced on the SiC surface by a defocused fs laser method. Meanwhile, a two-step laser-inducing method was proposed to fabricate an array of two-dimensional square-shaped nanocolumns with a size of 60 nm × 60 nm. The two-step laser-inducing method realized tuning in the surface nanostructure morphology and localized nanostructures rewriting by adjusting the laser processing parameters. This large-area periodic structure inducing method showed the possibility of making laser-writing technology to be flexible, straightforward and, hence, competitive for advanced industrial application based on surface nanostructuring.