Laser Travel Speed Research Articles

Wear and corrosion properties of laser treated Cr2O3 on stainless steel

In this study, a highly wear and corrosion resistance coating was fabricated on 304 stainless steel. Herein, air plasma spray coating of Cr2O3 was deposited on 304SS which was subsequently treated with laser at different travel speeds these were: 25 mm/min, 50 mm/min and 100 mm/min, respectively. The morphology of coatings was studied by using scanning electron microscopy. It revealed that ultrafine grain structure is found as travel speed is increased, the as-solidified microstructure got more and more refined. Wear test demonstrated that with increase in laser t speed, the wear rate increaased. Furthermore, wear rate of laser treated coating at travel speed of 25 mm/min exhibits very comparable result at 8 N and 16 N. The potentiodynamic polarization results described that pitting potential was increased and current density (Icorr) was decreased two orders of magnitude for laser treated coating at travel speed of 25 mm/min as compared to faster laser scan rate

The Effects of Laser Power and Travel Speed on Weld Geometry in the case of Manual Laser Welding

In our research, we investigated the effects of laser power and travel speed on the weld geometry in case of manual laser welding. Our experiments revealed that a characteristic two-part weld geometry is obtained under our experimental parameters. It was also found that increasing the laser power leads to a nearly linear increase in the weld width, while increasing the travel speed leads to a decrease in the weld width. The penetration depth does not increase further above a certain power level. A decrease in travel speed results in an increase in penetration depth. At the travel speeds tested, a narrow and deep weld geometry was obtained at the 70-80 % power level and a wider but shallower weld at the 90-100 % laser power level.

Effect of laser cleaning on adhesive properties of carbon fiber composite materials

A pulsed fiber laser was used to conduct laser cleaning experiments on the composite paint layer on the surface of carbon fiber composite materials (carbon fiber-reinforced plastic (CFRP)). The influence of laser energy density and laser travel speed on the cleaning effect was studied. The surface morphology, surface roughness and phase composition of the cleaned sample were analyzed. After bonding, tensile testing was conducted on the bonding part to verify the impact of laser cleaning on the bonding performance. The research results indicate that the cleaning effect gradually improves with the increase of laser energy density or the decrease of travel speed. In this experiment, when the laser energy density is 4.00[Formula: see text]J/cm2 and the travel speed is 6.5[Formula: see text]mm/s, the phase composition of the cleaned substrate surface is only C, without TiO2 and BaSO4. This indicates that the paint layer has been completely removed under this process parameter. By selecting reasonable process parameters, the surface paint layer of CFRP can be effectively removed, and a good surface morphology can be obtained without damage to the carbon fiber. Meanwhile, the mechanical properties after bonding can be improved.

Single track analysis of additive manufactured SS 316L based composites using powder bed fusion

The inadequate wear resistance and hardness of SS 316L make it unsuitable for use in harsh mechanical conditions. The present study reports the deployment of powder bed fusion (PBF) to create B4C particle-reinforced SS 316L composites to improve the mechanical properties of SS 316L. The study focuses on the influence of PBF process parameters on the track width (TW), track depth (TD), surface morphology, hardness, and surface roughness of a single track. TW and TD both increase with laser power (LP). The maximum hardness of 328 HV and minimum surface roughness of 0.07 µm are seen at LP of 300 W, and laser travel speed of 0.06 m/min. The absence of B4C particles is noticed at high laser powers due to the low density of reinforcement particles.

State of art: Review on laser surface hardening of alloy metals

Surface hardening treatments are performed to increase the hardness, wear resistance, durability and their micro structural properties. After the development of High-Powered Diode Lasers (HPDL), the laser surface hardening process is widely applied due to their non-contact treatment process, rapid cooling without any medium, controlled method of heat treatment and depth with automation and precision with relatively minimum energy input. Laser surface hardening of steels, carbon alloys, iron and other metals in manufacturing of components, stamping and forging dies, tools and other components in the field of mechanical, automotive and metallurgical have shown a positive progression in hardness and wear resistance with controlled phase changes. The factors of laser power density and travel speed plays key roles in phase changes and the surface transformation hardening. The surface hardening of heavily loaded components under motion should possess good surface roughness, tribological characteristics of wear resistance, hardness and temperature coefficients. Thus, laser surface hardening is optimum, controlled and economic way of surface treatment processes in manufacturing of mechanical components.

Performance of ANN in predicting the depth to width ratio and tensile strength of UNS S32750 laser weld joints

The effectiveness of the pulsed mode laser weld joint is characterized by the supply of optical energy to the interface. The laser welding process parameters, such as laser power, pulse duration, travel speed and focus, determine the efficacy of the weld, which is defined by full penetration and free of pores and defects. However, expressing the relationship between various process parameters and mechanical strength is intricate due to the prevalence of non-linear relationship. The development of computational approaches aids in optimizing the laser welding parameters and reducing trial and error. Hence, the artificial neural network (ANN) model is developed, in a python environment, to predict the optimum process parameter values for a desirable depth to width ratio and maximum tensile strength of UNS S32750 laser butt weld joints. The developed model was assessed by experiments, not utilized for training. The ANN model predicts the depth to width ratio and tensile strength of the weld joints with an accuracy of 90% and less than 10% divergence from the experimental result. Furthermore, for the process, parametric conditions are: (power: 550 W, focus: –1 mm, pulse duration: 13 Hz and travel speed: 136 mm/min) to attain maximum tensile strength.

Experimental and theoretical investigation of the formation of the surface layer highly alloyed with aluminum

Laser surface treatment is a complex process in which, under the influence of a laser, the surface of material melts, while changing its structure and properties. In this paper, we consider the simulation of the process and present the results of studying the influence of laser processing parameters on the dimensions of the melt pool. The main purpose of the study is to reveal the dependence of the depth of the melt pool, namely the thickness of the layer in which the mixing process of the components takes place, on the laser parameters. As a result of the study, it was found that after laser treatment of the surface of samples with a coating thickness of 20, 40 and 80 μm at a beam speed of 100 mm/s and power of 180 W, the coating material is completely mixed with the substrate. It is also shown that with the laser travel speed 400 and 800 mm/s and the power 180 W, there is no mixing of the components in the impact zone, since the energy input is not enough.

A simplified modelling approach for thermal behaviour analysis in hybrid plasma arc-laser additive manufacturing

Hybrid plasma transferred arc (PTA)-laser additive manufacturing (AM) has the potential to build large-scale metal components with high deposition rate and near-net shape. However, the process is complex with many parameters adjustable for process control, which determine the thermal behaviour and thus the final structure and properties of the deposited components. In this study, a three-dimensional steady-state finite element model with two independent circular surface heat sources was developed, validated, and used to analyse the thermal behaviour in hybrid PTA-laser AM of Ti-6Al-4V. Artificial conductivity in three orthogonal directions was applied in the melt pool to compensate for the melt pool convection effect. The predicted melt pool geometry, heat-affected zone and thermal cycles had good agreement with the corresponding experimental data. This model has advantages over the widely used volumetric heat source model, since it is more representative of the energy sources used, giving accurate thermal prediction for a wide range of process parameters. As the heat source parameters in this model are directly linked to the actual arc/laser size, it enables to capture heat source size effect on the hybrid process. In addition, it is easier to calibrate compared to the model with volumetric heat sources due to the fewer empirical parameters involved. It was found that in the investigated ranges of all the parameters, the melt pool geometry is more sensitive to laser power and travel speed compared to arc-laser separation distance and laser beam size. The full-field distributions of the cooling rate and temperature gradient in the hybrid process were obtained and the roles that different process parameters played on them were also studied, which provided useful thermal information for metallurgical analysis.

Effects of processing conditions on the solidification and heat-affected zone of 309L stainless steel claddings on carbon steel using wire-directed energy deposition

Directed energy deposition and laser cladding technologies are suitable advanced manufacturing techniques for applying corrosion-resistant claddings to large carbon steel components. In this work, we clad 309L stainless steel wire onto carbon steel substrates and examine the effects of processing parameters (laser power and travel speed) on metallurgical bonding and microstructures. Wire dripping defects correlate to excessive heat input, while cracking, stubbing and delamination defects are linked with insufficient heat input. Spectroscopic scans of the weld microstructure show the amount of base metal mixing in the weld is a function of processing parameters and the number of cladding layers. In the first cladding layer, the weld metal is diluted with base metal ranging from 1.7 to 45.6 %; this amount dramatically decreases in the second layer (0–8.6 %), promoting primary ferrite solidification, which decreases solidification cracking susceptibility. Martensite forms in the heat-affected zone from the high cooling rates associated with laser processing. Subsequent laser passes temper the martensite and carbon diffuses from the substrate into the first cladding layer. Cladding two or more layers is beneficial for mitigating defects, lowering dilution, and producing a highly alloyed surface suitable for corrosion protection.

Technological Assurance of Ti-6Al-4V Parts Produced by Additive Manufacturing Using Selective Metal Laser Sintering

Abstract The research relates to a technological assurance of Ti6-Al-4V parts produced by additive manufacturing (AM) by means of a metal laser sintering, especially by a fibre laser 3D printer. The influence of technological parameters such as layer thickness, hatch spacing, laser travel speed and laser power have been analysed as well as the influence of thermal treatment as a post processing method has been studied. Technological parameters in combination with a thermal treatment present a challenge in order to manufacture satisfactory products in terms of mechanical properties. The research guides through different phases of experiments to distinguish the best technological parameters. The following research may be used for further investigation of technological assurance for additive manufacturable parts as well as forms the springboard for further research in development of new titanium composites using additive manufacturing methods.

Surface texture characterization for thin-wall NASA HR-1 Fe–Ni–Cr alloy using laser powder directed energy deposition (LP-DED)

Additive Manufacturing (AM) offers new design and manufacturing opportunities of thin-wall microchannel heat exchangers for aerospace and industrial applications. Laser Powder Directed Energy Deposition (LP-DED) is an AM process providing large scale manufacturing of thin-wall microchannel heat exchangers. Successful industrialization of the LP-DED process requires critical quantification and understanding of the metallurgical, geometric, and process limitations. Specifically, understanding the as-built surface texture, inclusive of roughness and waviness, is significant due to its effects on the friction factor and pressure drop within a heat exchanger. This experimental study completed a design of experiments (DOE) to determine the critical build parameters that impact surface texture for enclosed thin-wall samples. This study summarizes the characterization work of the LP-DED process for 1 mm enclosed walls with an Fe–Ni–Cr (NASA HR-1) alloy. The LP-DED parameters including laser power, powder feedrate, travel speed, layer height, and rotary atomized powder feedstock were modified in the experiment. An evaluation of the DOE samples and resulting surface texture is provided along with conclusions from these experiments. Results indicate that 3D areal and 2D profile (directional) surface texture is estimated by 2x the powder diameter that becomes captured or partially melted on the trailing edge of the melt pool. The fine powder showed a higher sensitivity to parameter changes but resulted in a higher density material and 23% reduction in roughness. Surface texture was also shown to vary between closed channel shapes (internal) due to ricochets, recirculation, and higher volume of powder available to bond compared to external (outer) surfaces. The understanding of the LP-DED process as-built surface texture is essential to fluid flow applications such as heat exchanges and can modify performance for enhanced heat transfer or can be a detriment to pressure drop.

Laser strengthening of additive manufactured edge seal for vacuum insulated glazing with micro-size glass frit

Sealing of glass edge is a key step in developing cost-effective and durable vacuum insulated glazing for the drive towards net-zero energy buildings. To achieve a high-strength sealing with scalable and low-cost processing, we investigated a novel sealing method based on additive manufacturing and laser process and reported quantitative analysis of the laser assisted method sealing strength and the requirement of vacuum insulation glazing. Micro-size glass frits in printing ink and a continuous-wave laser curing were employed to allow the formation of a hermetic bonding layer with low thermal budget. Controlling various sealing parameters including laser traveling speed, spot diameter, and laser power, the water seepage and mechanical strength of the resulting glass-to-glass bonding were examined. Through the response surface methodology, we identified the optimized sealing condition where the bonding strength reached 5.68 MPa. A comparation of the bonding strength between thermal sealing method and laser-assisted method has been analyzed as well.

Fatigue life optimization for 17-4Ph steel produced by selective laser melting

PurposeThe mechanical characterization of selective laser melting (SLM) parts is an industrial challenge. This paper aims to propose a methodology to control the fatigue life of 17-4Ph stainless steel by selecting the most relevant manufacturing parameters: i.e. laser power, laser travel speed, hatch spacing and laser defocusing.Design/methodology/approachA rough and refined design of experiment (DOE) is carried out to target the best combination of process parameters. A response surface model is then constructed to predict the parameter combination that optimizes the fatigue performance.FindingsThis study results show that the fatigue limit of the specimens manufactured by SLM (471.7 MPa at 107 cycles) has reached near 90% of the value found in samples machined from a bar. This demonstrates the applicability of the method proposed to optimize the SLM process and control the fatigue life of 17-4Ph stainless steel. The study results are compared with other research works and provide an increase of 18% to the fatigue limit.Originality/valueThis study showcases a DOE methodology to optimize the SLM parameters to achieve fatigue performance as great as that of solid 17-4Ph stainless steel.

Bead Geometry Prediction in Laser-Wire Additive Manufacturing Process Using Machine Learning: Case of Study

In Laser Wire Additive Manufacturing (LWAM), the final geometry is produced using the layer-by-layer deposition (beads principle). To achieve good geometrical accuracy in the final product, proper implementation of the bead geometry is essential. For this reason, the paper focuses on this process and proposes a layer geometry (width and height) prediction model to improve deposition accuracy. More specifically, a machine learning regression algorithm is applied on several experimental data to predict the bead geometry across layers. Furthermore, a neural network-based approach was used to study the influence of different deposition parameters, namely laser power, wire-feed rate and travel speed on bead geometry. To validate the effectiveness of the proposed approach, a test split validation strategy was applied to train and validate the machine learning models. The results show a particular evolutionary trend and confirm that the process parameters have a direct influence on the bead geometry, and so, too, on the final part. Several deposition parameters have been found to obtain an accurate prediction model with low errors and good layer deposition. Finally, this study indicates that the machine learning approach can efficiently be used to predict the bead geometry and could help later in designing a proper controller in the LWAM process.

Bead shape control in wire based plasma arc and laser hybrid additive manufacture of Ti-6Al-4V

Wire based plasma transferred arc (PTA)-laser hybrid additive manufacture has the potential to build large-scale metal components with high deposition rate and near-net shape. In this process, a single bead is the fundamental building block of each deposited component, and thus the bead shape control is essential for the deposition of different geometries. However, how to control the bead shape by manipulating various process parameters is still not understood. In this study, the effect of different process parameters, including laser power, energy distribution between the PTA and laser, wire feed speed, travel speed, and laser beam size on the deposition process and bead shape was investigated systematically. The results show that the optimum operating regime for the hybrid process is with the wire being fully melted by the PTA and the melt pool being controlled by the laser, which gives a good bead shape as well as a stable deposition process. The bead shape is significantly affected by the laser power and travel speed due to the large variation in energy input. The effect of wire feed speed is more complex with the bead width initially increasing to a maximum and then decreasing as the wire feed speed increases. The laser beam size has a minor effect on the bead shape, but a small beam size will result in an irregular bead appearance due to the unstable process caused by the high power density. In addition, a procedure for controlling the bead shape in the hybrid process was proposed, which provided a reference for selection of different process parameters to achieve required bead shapes. The feasibility of this proposed procedure was demonstrated by the two deposited multi-layer single-pass walls. • The bead shape control in wire based plasma arc-laser hybrid additive manufacture was investigated. • The effect of different process parameters on the deposition process and bead shape was obtained. • A procedure for selecting different process parameters for achieving required bead shapes was proposed. • The feasibility of the proposed procedure was demonstrated by the deposited multi-layer single-pass walls.

Modelling and optimization of process parameters to obtain maximum tensile strength for laser butt welding of 316L austenitic stainless steel sheets

The attribute of high power density but low energy-input in Laser welding offers exciting solutions to the commonly encountered disadvantages with conventional joining techniques.In this paper, 316L Austenitic Stainless Steel metal sheets were butt welded using Nd:YAG Laser welding system. Owing to its low cost and specific properties such as excellent toughness, higher creep, stress to rupture at elevated temperatures, 316L A.S.S finds wide range of applications in the industrial arena especially in the automobile and marine sectors. Hence, it becomes imperative to examine its post weld properties after performing laser welding and find optimized values of the parameters. The prominent process parameters like Laser Power, Travel speed and Focal length were analysed and optimised.Design of experiment statistical tool was embraced for the systematic conduct of the tests. Response Surface Methodology (RSM) and analysis of variance (ANOVA) techniques were employed to identify the significant process parameters affecting the weld. An empherical relationship involving the parameters was developed to predict the ultimate tensile strength. The 3D response surface plot and contour plots were generated for this model to elucidate the interaction effect of Laser parameters (Travel speed and Focal length), (Laser Power and Focal Length) & (Laser Power and Travel Speed) on Ultimate Tensile Strength.The welded specimens cut by electric discharge machining were prepared for tensile testing as per the ASTM standard. The Universal Testing Machine was used to test the welded specimen. Microhardness Testing was also carried out on the base material and the Heat Affected Zone (HAZ) using Vickers Hardness Testing machine. The tensile tested specimens were used for metallurgical analysis using Scanning Electron Microscope (S.E.M.). Specimen prepared for metallurgical analysis were sectioned, mounted, ground and polished in accordance with recommended procedures in ASTM practice E 3-11. The metallurgical observations showed the existence of undulating topography of ductile fracture surfaces. The investigations reveals that the actual values of the Ultimate tensile strength of the weld were falling close with the predicted strength obtained through the proposed model. It can be concluded that the proposed model in this work can be utilised to predict tensile strength of the weld with more precision.

Modeling and optimizing the laser parameters for corrosion resistance in 316 SS laser hardfaced surface using tungsten carbide

Laser hardfacing Tungsten Carbide was fabricated on 316 stainless steel surfaces using a synchronization powder feeding technique by 4 kW Diode laser (co axial laser) apparatus. An attempt has been made to optimizing the process parameters of laser such as Laser Power (P), Travel Speed (T), Defocusing Distance (D) and Powder feed rate (F). The influence of the processing variables on corrosion rate is discussed. The experiments were conducted using design matrix based on a four factor and five level central composite rotatable design. An empirical relationship was developed to predict the corrosion rate of Tungsten carbide hardfaced layer using response surface methodology (RSM) technique. The optimized parameters and the influenced parameter were identified. The interaction effects of input process parameters of laser hardfacing were discussed. The corrosion properties were analyzed by Pitting corrosion method. The pitting method results show that the hardfacing is mainly to increase the corrosion resistance. With the increase of laser power, corrosion resistance and micro hardness of the hardfaced surface have been improved.

Laser Transformation Hardening of EN24 Alloy Steel

Abstract The intention of improving the surface hardness, wear resistance, sliding and rolling contact fatigue properties without affecting the material core or in other words minimizing the distortion caused to the inner core of the material due to heat treatment processes has led to the development of Selective Hardening Methods (SHM), like flame hardening, induction hardening, laser hardening, electron beam hardening, ion implantation, selective carburizing and nitridingetc,. An experimental investigation of laser surface hardening of EN24 alloy steel using Nd-YAG laser in atmospheric medium was conducted to understand the influence of laser parameters like laser power, travel speed on the microstructure and material hardness. The laser heat input is allowed to harden the surface of the material by varying laser beam power (500W-3000W) and travel speed (1500-5500mm/min) of the worktable. The laser heating provides localized surface treatment without altering the mechanical properties of the material, leaving the core properties unaffected. The conventional heat treatment followed by rapid quenching distorts the material leaving differential material properties, downgrading the material unfit for highly stressed mechanical applications. EN24 is high tensile alloy steel used in applications like gears, axles, kicker rods, bolts pump shafts and turbine rotors. Microstructure study revealed the transformation of martensitic structure with evident carbides formation with substantial increase in surface hardness of EN24 alloy steel. The case depth relationship with laser parameters were analyzed and documented. The microstructure of laser hardened EN24 alloy steel revealed the formation of martensite along the laser hardened zone (widthwise) boundary and martensite along with transformed carbides beneath the laser hardened surface (depth wise). The surface hardness ranging between 50 HRC and 57 HRC at 2.1 kW laser power with precise directional travel of 3500 mm/min to 4000 mm/min with diffusion less martensitic transformation was observed. Undistorted phase transformation, consistent surface hardness with precise process controls can be achieved using laser hardening of mechanical components

High-throughput screening of laser additive manufactured metallic glass via ultrasonic wave

Laser additive manufacturing (LAM) technology provides an opportunity to fabricate bulk metallic glasses (BMGs) without any dimensional constraint and achieve the large-scale applications of BMGs. However, flaws, such as cracks, gas porosity, and crystalline phases, are always formed accompanied by the process of LAM, which seriously worsens the mechanical and physical properties of the resulting BMGs. Here, we present a novel method that involves ultrasonic wave technique to high-throughput screen the optimum process parameters for the LAM of BMG. A parameter library, constituted by a series of rectangular BMG samples, is rapidly fabricated by the LAM method under continuously changed combinations of laser power and travel speed. The ultrasonic attenuation factor, which is sensitive to the flaws, is used as the monitor to screen the parameters of the BMGs fabricated by the LAM. Using this approach, the laser power of 1300 W and travel speed of 600 mm/min are estimated as the optimum parameter combination for the LAM of a Zr51Ti5Ni10Cu25Al9 (Zr51) BMG with the slightest flaws. The amorphous-phase dominated microstructure and the sufficiently high tensile strength of the subsequent fabricated large-sized Zr51 BMG sample verify this optimum parameter combination.

Surface transformation hardening of ductile cast iron by a 600w fiber laser

Laser transformation surface hardening of the forming edges of large mold made of nodular cast iron has gained momentum in recent years. In this investigation a 600 w fiber laser was employed to harden GGG-60 cast iron. It is found that to achieve the optimum surface properties, the combination of laser power density and travel speed has to be set such that to dissolve the carbides but not that high to dissolve the graphite nodules. The response of a hardened track to a second thermal cycle by a neighboring laser track in terms of both tempering and re-hardening showed that by increasing the overlapping, a more uniform surface microstructure and hardness is obtained. In addition by employing differential scanning calorimetry (DSC) analysis the maximum “Hardening Ratio” by the fiber laser as the power source for GGG-60 cast iron was found to be 15.3 %.