Surface Modification of Carbon Fiber Polymer Composites after Laser Structuring

Cyclic fatigue delamination of carbon fiber-reinforced polymer-matrix composites: Data analysis and design considerations

Silicon carbide (SiC) microchannels show their promising merits in the applications of microchannel heat sink cooling systems, microsensor MOS devices, and UV photodiodes. The fabrication of SiC microchannels is critical for their wide applications. In this study, a laser micromilling method is utilized to process SiC microchannels. A series of SiC microchannels are fabricated using a pulsed fiber laser. Based on the SEM observations and 3D confocal microscope measurements, the formation of microchannels is analyzed. The effects of laser processing parameters, such as laser output power, scanning speed, and scanning times as well as the predetermined microchannel width, on the geometric dimension and surface morphology are systematically assessed. The common recast layer deposited around the laser-scanned areas in the laser micromilling of metallic structures was not found for the SiC microchannels. A transition between triangular and trapezoidal shapes occurred for the laser-micromilled microchannels depending on the processing parameters and predetermined width. The microchannel depth increased monotonically with the laser output power and laser scanning time but decreased with increasing scanning speed. On the contrary, the bottom width of microchannels presented an inverse trend. The surface roughness was dependent on the laser scanning speed, scanning time, as well as predetermined width.

Ti-6Al-4V alloy biomaterials have low hardness, wear resistance, high corrosion rate and toxicity as results of release of aluminium and vanadium ions that led to the premature failure of the implant. In order to overcome some of these problems, laser cladding of Ti6Al4V alloy with Niobium was conducted. Three laser parameters (laser power, beam diameter and laser scan speed) were used to ascertain the proper operating condition for this laser process. Rofin Nd: yag laser was used in the laser cladding. The electrochemical study was conducted using Hank's buffered salt solution an environment similar to the human body. The optimum improvement in corrosion resistance resulted to 81.79% when compared with substrate. It has been established that operating parameter for laser cladding of Nb on Ti6Al4V were obtained at: laser power (1,000 W), beam diameter (1 mm) and scan speed (0.3 m/min).

In order to achieve high-performance coatings on the surface of electric submersible pump impellers, it is crucial to optimize the laser cladding process parameters. Using Ansys 2021 R1 commercial software, a numerical simulation of laser cladding Ni60 powder on high nickel cast iron was conducted. The simulation utilized a 3D Gaussian heat source, parametric language, and life–death unit technology to replicate the characteristics of synchronous powder delivery laser cladding. The study focused on analyzing the temperature field cloud map and molten pool size under different laser power and scanning speeds, narrowing down the process parameter window, selecting optimized laser power and scanning speed, and assessing the changes in surface morphology, melting height and width, dilution rate, microhardness, and microstructure of the laser cladding coating. Results indicate that the coating width and thickness increase with higher laser power and lower scanning speeds. The microstructure consists primarily of dendritic, block, short rod, and long strip formations, and exhibits a tightly distributed and uniform grain structure. Furthermore, the microhardness of the coating shows a negative correlation with laser power and scanning speed. The optimal process parameters were determined to be a laser power of 1100 W and a scanning speed of 6 mm/s. A comparison with the simulation confirmed the effectiveness of the simulation in effectively guiding actual production.

One-step brazing process to join CFC composites to copper and copper alloy

Microstructural and mechanical properties of complex phase steel to aluminium alloy welded dissimilar joint

A three-dimensional (3D) selective laser melting (SLM) model comprising coupled heat transfer and flow behavior is proposed. The free surface of the melt pool is calculated by the volume-of-fluid (VOF) method, which is a means of acquiring the surface morphology. In this research, laser powers and laser scanning speeds were normalized to characterize the influence on the surface morphology. Results showed that when the scanning speed was increased, the surface morphology initially became flatter, but then roughness developed again at high speed case. Further, as the laser power was increased, the surface morphology gradually roughened. To better describe the surface-morphology phenomenon according to different laser parameters, the melt pool volume and melt pool lifetime were also investigated. With these two factors constrained, a fine surface could be obtained with a low melt pool volume and proper lifetime (approximately 100 to 130 μs). The surface morphology and the width of the melt track were experimentally acquired, and are in a good agreement with the results predicted by simulation.

The present study aims at analysing the combined role of laser power (LP) and scanning speed (SS) on the surface topography and dimensional accuracy of Titanium (Ti–6Al–4V) alloy fabricated through a laser-based powder bed fusion process. The widespread volumetric energy densities (VEDs) ranging from 25 J/mm3 (S1) to 120 J/mm3 (S10) were chosen with five different combinations of LP with varying SS, such as 150 W (276 and 850 mm/s), 250 W (630 and 990 mm/s), 300 W (395 and 465 mm/s), 350 W (405 and 1100 mm/s), and 370 W (850 and 1270 mm/s). Sample S1 (25 J/mm3) revealed the presence of partially melted track and VED beyond 60 J/mm3 producing a detrimental surface quality due to over-burning. At low LPs of 150 and 250 W, a reduction in SS led to a decrease in surface roughness, owing to sufficient melting of the powder layers. Meanwhile, at high LPs of 300 and 350 W, a reduction in SS caused the burning of the layer which led to an increase in the roughness. In contrast, at a high LP of 370 W, a reduction in SS caused a decrease in the roughness parameters. Both LP and SS were found to have strong interdependence in the achievement of the as-built surface quality. Further, the samples fabricated with excessive VED S7 (75 J/mm3), S8 (90 J/mm3), S9 (105 J/mm3) and S10 (120 J/mm3) caused delamination of layers and resulted in severe angular distortion.

Due to the characteristics of high hardness, wear resistance, corrosion resistance, excellent thermal shock resistance, and low thermal expansion coefficient, Si₃N₄ ceramics are widely used in aerospace, national defense, electronic and electrical, mechanical, chemical, and other fields. In this paper, the grooving experiments of Si₃N₄ ceramics were carried out by using a novel dual-beam coupled nanosecond pulse laser, and the influence of laser power and scanning speed on the surface morphology and geometric size of grooves were studied. The results show that the laser power has a significant effect on the surface morphology and geometric size of grooves. With the increase of laser power, the laser power density augments, and the width and depth of grooves increase. The groove width and groove depth first increase and then decrease with the increase of scanning speed, and both the groove width and depth reach the maximum value at scanning speed of 800 mm/min.

Tungsten has been widely used in many industrial fields due to its excellent properties. However, owing to its characteristics of inherent brittleness at room temperature and high melting point, it is difficult to prepare tungsten parts with high complexity via traditional methods. In the present work, tungsten samples were prepared by laser powder bed fusion. The influence of each process parameter including laser power, scanning speed, and hatch spacing on the surface morphology, densification, and microstructure of tungsten samples was systematically investigated. The results showed that the use of the appropriate parameters, especially high laser power, can effectively improve the surface quality and obtain a dense surface. The tungsten samples with a relative density of 98.31% were obtained with optimized parameter combinations: a laser power of 300 W, scanning speed of 400 mm/s, and hatch spacing of 0.08 mm. Compared with scanning speed and hatch spacing, the laser power had a more obvious influence on the relative density. Additionally, for the grain morphology by microstructure inspection, elongated curved grains gradually transformed into fine straight columnar grains as the scanning speed increased. The hatch spacing would change the grain morphology slightly but had no significant effect on the grain size.

In recent years, reducing the size and weight of consumer products requires the joining of thin sheets of magnesium alloys with both thickness and joining area of less than 1mm, especially for packaging purposes. Conventional welding processes are difficult to joint a thin sheet magnesium alloy because of high heat input, which in turns leads to various problems such as burn through and cracks. In this study, lap fillet welding of thin sheet magnesium alloy AZ31B with a thickness of 0.3 mm has been carried out using a pulsed Nd:YAG laser beam. The influences of gap, laser beam center location and scan speed on joint appearances have been investigated. It was found that defects were significantly reduced when the gap width was less than 35 µm when the laser beam center was located just on the edge of the upper specimen (x=0), and scan speed was varied from 400 to 450 m/min. Wider bond width at average value of 300 µm was achieved when the beam center was at x=0 with a wide range of scan speeds from 250 to 450 mm/min compared with the cases at x=-0.1 and -0.2 mm from edge. Increases in bond width and minimal defects at x=0 improve fracture load by 68% compared with those at x=-0.1 mm.

Experimental study and neural network model based prediction of layer thickness influence on LPBF IN625 single track geometry

Silicon carbide (SiC) exhibits intriguing thermo-physical properties such as higher heat capacity and conductivity, as well as a lower density than Ti6Al4V(ELI). These properties make SiC a good candidate for the reinforcement of Ti6Al4V(ELI) with respect to its use as a heat shield in aero turbines to increase their efficiency. The traditional materials used in aircraft structures were required to have a combination of good mechanical properties such as strength, stiffness, and hardness and low weight, as well as low thermo-physical properties such as coefficient of thermal expansion (CTE) and thermal conductivity. The alloy Ti6Al4V(ELI) has a density of 4.45 g/cm3, which is lower than that of structural steel (7.4 g/cm3) and higher than that of aluminium (2.5 g/cm3). Lower density benefits light weighting. Aluminium is the lightest of the traditional materials used but has relatively low strength. The CTE of SiC of 4.6 × 10-6/K is lower than that of Ti6Al4V(ELI) of 8.6 × 10-6/K, while the density of SiC of 3.21 g/cm3 is lower than that of Ti6Al4V(ELI) of 4.45 g/cm3. Therefore, from the theory of composites, SiC/Ti6Al4V(ELI) composites are expected to have lower densities and CTEs than those of Ti6Al4V(ELI), thus providing for lightweighting and less thermal related buckling or separation at their joints with carbon/epoxy resin panels. The specific strength, stiffness, and Knoop hardness of SiC of 75-490 kNm/kg, 132 MNm/kg, and 600-3800 GPa, respectively, are generally larger than those of Ti6Al4V(ELI) of 211 KNm/kg, 24 MNm/kg, and 880 GPa, respectively. Therefore, investigating reinforcement of Ti6Al4V(ELI) with SiC particles is worthwhile as it will lead to the formation of composites that are stronger, stiffer, harder, and lighter, with lower values of CTE. For additive manufacturing, this requires initial studies to optimise the process parameters of laser power and scanning speed for single tracks. To print single tracks in the present work, different laser powers ranging from 100 W to 350 W and scanning speeds ranging from 0.3 m/s to 2.7 m/s were used for different SiC volume fraction values of values. To print single layers, different values of hatch distance were used together with the best values of laser power and scanning speed determined elsewhere by the authors for different volume fractions of SiC. Through optical microscopy, the built tracks and their cross sections were examined. By using laser power and scanning speeds of 200 W and 1.2 m/s, and 150 W and 0.8 m/s, respectively, the best tracks at 5% and 10% volume fractions were obtained, whereas the best tracks at 25% volume fraction were achieved using a laser power of 200 W and a scanning speed of 0.5 m/s. Furthermore, the results showed that the maximum SiC volume percentage of 30% resulted in limited or no penetration. Therefore, it is concluded from the study that parts with improved mechanical properties can be produced at SiC volume fractions ranging from 5% to 25%, while parts produced at the high volume fraction of 30% would have unacceptable mechanical qualities for the final part.

Microstructure and mechanical properties of WC-12Co cemented carbide fabricated by laser powder bed fusion on a WC-20Co cemented carbide substrate

Effect of pulsed Nd:YAG laser processing parameters on surface properties of polyimide films