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Experimental Investigation Of Quality Characteristics In Nd:YAG Laser Drilling Of Stainless Steel (AISI 316)
摘要： Micro-machining of advanced engineering materials such as stainless steels, titanium alloys, nickel alloys, and ceramics is a challenging task due to properties like high strength to weight ratio, toughness, slenderness ratio, and low thermal conductivity. Stainless steel of grade AISI 316 has wide applications in medical science, automobile engineering, aviation, and aerospace industry due to their favourable material properties such as low thermal conductivity, high corrosion resistance, and high strength to weight ratio. Micro-machining of AISI 316 with high aspect ratio is a difficult task due to excessive heat generation, micro- structural changes, and tool breakage. Laser beam machining (LBM) process is a suitable alternative machining process, since it localizes the heat source to control the micro-structural changes. The difficulty arises during laser drilling because of spatter area and heat affected zone (HAZ), which adversely affects the quality of laser drilled holes. The present study attempts to experimentally investigate the effect of laser process parameters such as pulse width, laser energy, pulse frequency, and flushing pressure on the performance measures such as spatter deposition and heat affected zone (HAZ) during drilling operation. To reduce the total number of experimental run and obtain maximum information for the experimental trials, Taguchi L27 has been adopted. Analysis of variance (ANOVA) is performed to identify significant laser parameters influencing both the performance measures. From the study, it is revealed that pulse width is the most significant parameter in the formation of spatter and HAZ. From the results, it is identified that spatter area initially increases with increase in pulse frequency and then decreases for any level of pulse width. As pulse frequency increases, laser power increases resulting in more heat input into the material. This causes increase in vapour pressure inside the laser drilled hole, more material ejection, and increase in spatter area. However, laser supported absorption (LSA) waves developed at higher value of pulse frequency brings about blockage of laser energy from the material surface as an engrossing plasma, which results in reduction of material ejection and reduction in spatter area. It is observed that HAZ increases with increase in pulse width and pulse frequency. It may be due to higher average power of the laser beam, which is directly proportional to pulse width and pulse frequency. Higher the value of pulse width, higher will be the laser thermal energy and higher HAZ.
关键词： Laser Drilling,Nd:YAG Laser,HAZ,Spatter
更新于2025-09-12 10:27:22
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Effects of processing parameters on the micro-drilling through fast hole electroerosion and laser trepanning in Inconel 718
摘要： Electroerosion and laser drillings are techniques used in manufacturing microholes in materials that are difficult to machine. Small diameter holes (between 0.18 and 2 mm) are commonly used in the aeronautical industry and gas turbine components as elements of the cooling system of hot side blades. This study aims to evaluate the effect of different machining parameters on the dimensional and microstructural quality of microholes obtained by the two manufacturing techniques cited. These effects were yield and dimensional analysis, the presence of micro-cracks, and width of the zone affected in the micro-drilling of Inconel 718. For this, microholes were produced through fast hole drilling electroerosion, using two electrode materials, copper and brass, and through Nd:YAG laser micro-drilling by trepanation. A central composite statistical design was defined to evaluate the influence of input parameter variations. Results were compared and showed that although the laser trepan process productivity is higher than that of electroerosion, laser drilling generates a greater concentration of cracks in the HAZ (heat-affected zone) when compared to the microholes manufactured by electroerosion. Therefore, assessment of the process to be used depends on the features one wants to optimize. Each manufacturing process has advantages and limitations that must be taken into consideration for selecting one of the techniques, and the project of the component should present the essential requirements for choosing the proper manufacturing process.
关键词： Inconel 718,Fast hole micro-drilling electroerosion,A central composite statistical planning,Laser micro-drilling by trepanation
更新于2025-09-11 14:15:04
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Proceedings [EAGE Publications BV 81st EAGE Conference and Exhibition 2019 - London, UK (2019.06.03-2019.06.06)] 81st EAGE Conference and Exhibition 2019 - Principal Investigation of Laser Jet Drilling Process and Field Implementation for Hard Rock and Geothermal Applications
摘要： This paper discusses the LaserJet Drilling lab and field test implementation results including fundamental investigations on laser-rock destruction/drilling mechanisms and related analysis and evaluation processes.
关键词： geothermal applications,rock destruction mechanisms,thermal drilling,hard rock,LaserJet Drilling
更新于2025-09-11 14:15:04
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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Comparison between ps- and μs-laser radiation for drilling holes for force transmission elements in CFRP-preforms
摘要： Current lightweight strategies in automobile, aerospace and wind energy applications include composite structures consisting of metal and fiber reinforced plastics for minimum weight, maximum force transmission and high material efficiency. Therefore, economic and technological beneficial material processing for the integration of force transmission elements such as inserts are crucial for these high performance materials. Current state of the art of machining carbon fiber reinforced material is to drill or mill the work piece after the consolidation process. Conventional mechanical and water jet processes lead to high tool wear and often non-repairable defects in the work piece such as delamination, fiber pullout, cracks in matrix and fibers, and deformation. Laser processing of the consolidated material can prevent force induced defects but leads to degradation of the matrix and leaves freestanding fibers inside the drilling hole which can damage the protective surface of subsequently inserted force transmission elements. This is especially critical for lifetime and performance during operation of the structural part. One solution is to drill the so called preform, prior to the infusion process, insert force transmission elements and subsequently infuse the preform with resin. Ultra sonic excited cutting knifes are not applicable for cutting hole diameters of a few millimeters with high aspect ratios. Punching as well as water jet cutting drop out due to force induced interaction with the textile or necessity of a subsequent drying process. Laser material processing could be an adequate solution to circumvent the above mentioned issues. Within this work, non-crimp carbon fiber (NCF) layers are investigated regarding laser processing via ultra-short pulsed and microsecond (fiber laser) radiation. The influence of different process parameters such as scanning speed, repetition rate and laser power are being evaluated regarding geometrical and materialographical quality such as conicity, textile swelling and heat affected zone (HAZ). The temperature distribution during laser processing is important for the estimation of when and where the knitting yarn, which keeps the carbon fiber plies together, disintegrates. Without the knitting yarn swelling occurs which is not desired for subsequent process steps.
关键词： force transmission elements,CFRP-preforms,microsecond laser,ultra-short pulsed laser,laser drilling
更新于2025-09-11 14:15:04
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Delamination-free millisecond laser drilling of thermal barrier coated aerospace alloys
摘要： Millisecond (ms) pulsed laser drilling is currently state-of-the-art in producing acute angle film cooling holes over aero-engine and gas-turbine components made from uncoated nickel superalloys. After laser drilling, most of these components are coated with a high-temperature thermal barrier coating (TBC) to maintain the temperature of the component at a level appropriate for its application. It is desirable to produce holes over the TBC coated components; however, the current state-of-the-art ms laser drilling of acute angle holes over TBC coated materials results in a high level of coating delamination and hence is not used in manufacturing industries. The recent introduction of ms quasi-continuous wave (QCW) fiber lasers has had a significant impact on industrial laser drilling. This paper reports the results of a fundamental investigation carried out on ms QCW laser drilling of angular holes over TBC coated superalloys and provides a pragmatic solution to the issue of TBC delamination. In addition to the investigation on traditional percussion and trepanning laser drilling processes, a new method of drilling called 'laser drilling post-laser TBC decoating' is evaluated with the aim of achieving delamination-free laser drilling of TBC coated aerospace alloy.
关键词： millisecond,thermal barrier coating,laser,drilling,angular,fiber,trepanning,TBC,hole,quasi-CW
更新于2025-09-11 14:15:04
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Dynamic interaction between a laser beam and keyhole front wall during fiber laser welding
摘要： A bright spot (laser beam spot-center-induced metal vapor) on the keyhole front wall (KFW) was observed during fiber laser keyhole welding of a ‘sandwich’ specimen to reveal the interaction between the laser beam and the KFW. The dynamic behavior of the bright spot shows that the keyhole formation is the result of periodical drilling of the laser beam spot center on the KFW during welding. Welding parameters have little effect on the drilling period. The drilling speed first increases and then decreases with the increase in the keyhole depth, and the next drilling process begins before the drilling speed reduces to 0 m s?1. The average drilling speed can be increased by increasing the line energy or power density of the laser.
关键词： keyhole front wall (KFW),drilling speed,interaction,fiber laser welding,period
更新于2025-09-11 14:15:04
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Adaptive neuro-fuzzy inference system based modeling of recast layer thickness during laser trepanning of Inconel-718 sheet
摘要： Re-solidification of molten material during the laser trepanning of Inconel-718 is a major hindrance in achieving good quality drill with high precision and accuracy. Re-solidification affects the performance of the drilled hole. Many researchers have tried for the optimization of laser trepan drilling in order to improve the drilled hole quality characteristics. But till now, limited work has been reported in concern with recast layer formation in laser trepan drilling of Inconel-718. This paper experimentally investigated the recast layer formation during laser trepan drilling followed by the prediction of the recast layer formation using the adaptive neuro-fuzzy inference system (ANFIS). Experiments are performed on 1.4-mm-thick Inconel-718 sheet using pulsed Nd: YAG laser. Recast layer thickness has been measured for each experiment followed by the ANFIS-based prediction of recast layer. Moreover, the effect of different input parameters on the recast layer has also been discussed.
关键词： Recast layer,Laser trepan drilling,Adaptive neuro-fuzzy inference system,Inconel-718
更新于2025-09-11 14:15:04
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Coaxial waterjet-assisted laser drilling of film cooling holes in turbine blades
摘要： Film cooling holes (FCHs) of nickel-based single crystal turbine blades were drilled by 532 nm Nd:YVO4 nanosecond laser in coaxial waterjet-assisted environment. Microstructure of the side wall of the FCHs was mainly investigated by means of transmission electron microscopy. The average thickness of heat affected zone (HAZ) around FCHs decreases with increasing of water flow rate. The main phase within HAZ evolves from β-NiAl to β-NiAl + γ-Ni with the increase in the water flow rate. Some γ-Ni particles in the HAZ twined along (111) plane. A small portion of the FCHs are free of HAZ when drilled by coaxial waterjet-assisted laser drilling at a laminar water flow rate ≥ 3.1 m/s. There are no processing-induced defects including HAZ, microcrack, and phase transformation around the FCHs when drilled at the water flow rate ≥ 5.1 m/s. The FCHs with high surface quality can be drilled by the coaxial waterjet-assisted laser drilling. Finally, effects of fluid water on drilling quality of the FCHs were discussed.
关键词： turbine blades,film cooling holes,Coaxial waterjet-assisted laser drilling,heat affected zone (HAZ),transmission electron microscopy (TEM)
更新于2025-09-11 14:15:04
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Investigation of hole quality in rotary ultrasonic drilling of borosilicate glass using RSM
摘要： The present article emphasizes on reducing the edge chipping and taper during rotary ultrasonic drilling of one of the most demanded ceramic glasses “BK-7.” Statistical tools of design of experiments and backing plate were adopted as two distinct approaches to curb the chipping damage. Central composite design has been conjugated with desirability function for framing the design matrix. This investigation also emphasizes to study the effect of process variables—spindle speed, ultrasonic power and feed rate—on the chipping width (CW) and taper (T). After developing the second-order regression models for the CW and T, analysis of variance was used to check the fitness of regression models and recognizing the significant model terms. Then impact of each process parameter was analyzed on responses of interest through 3-D surface plots. The feed rate came forth as the most dominating factor by having maximum influence over the qualitative aspects “CW” and “T” of the drilling process. Interactions of higher rpm and power with lower feed effectively reduced the CW and T. The backing material, employed during main experimentation, also proved its effectiveness to reduce CW when main experiments results were compared to the results of pilot experimentation, which was performed without backing plate. Scanning electron microscope (SEM) was used to analyze the different tool wear modes and microstructure of machined surfaces. Tool weight measurement revealed the dominance of bond fracture and grain fracture during the early stage of the drilling process. Apart from brittle fracture, SEM also affirmed the presence of plastically deformed regions over the machined surfaces. Little deviations between the predicted values and experimental values during the confirmatory tests validated the prediction accuracy of regression models at 95% confidence level.
关键词： Ultrasonic,Wear,Taper,Drilling,Optimization,RSM,Chipping,Desirability
更新于2025-09-04 15:30:14