Ytterbium Laser System Research Articles

The Effects of Sn Addition on the Microstructure and Surface Properties of Laser Deposited Al-Si-Sn Coatings on ASTM A29 Steel

Aluminium and its alloys have been successful metal materials used for many applications like commodity roles, automotive and vital structural components in aircrafts. A substantial portion of Al-Fe-Si alloy is also used for manufacturing the packaging foils and sheets for common heat exchanger applications. The present research was aimed at studying the morphology and surface analyses of laser deposited Al-Sn-Si coatings on ASTM A29 steel. These Fe-intermetallic compounds influence the material properties during rapid cooling by laser alloying technique and play a crucial role for the material quality. Thus, it is of considerable technological interest to control the morphology and distribution of these phases in order to eliminate the negative effects on microstructure. A 3 kW continuous wave ytterbium laser system (YLS) attached to a KUKA robot which controls the movement of the alloying process was utilized for the fabrication of the coatings at optimum laser parameters. The fabricated coatings were investigated for its hardness and wear resistance performance. The field emission scanning electron microscope equipped with energy dispersive spectroscopy (SEM/EDS) was used to study the morphology of the fabricated coatings and X-ray diffractometer (XRD) for the identification of the phases present in the coatings. The coatings were free of cracks and pores with homogeneous and refined microstructures. The enhanced hardness and wear resistance performance were attributed to metastable intermetallic compounds formed.

Generation of high-field terahertz pulses in an HMQ-TMS organic crystal pumped by an ytterbium laser at 1030 nm.

We present the generation of high-peak-electric-field terahertz pulses via collinear optical rectification in a 2-(4-hydroxy-3-methoxystyryl)-1-methilquinolinium-2,4,6-trimethylbenzenesulfonate (HMQ-TMS) organic crystal. The crystal is pumped by an amplified ytterbium laser system, emitting 170-fs-long pulses centered at 1030 nm. A terahertz peak electric field greater than 200 kV/cm is obtained for 420 µJ of optical pump energy, with an energy conversion efficiency of 0.26% - about two orders of magnitude higher than in common inorganic crystals collinearly pumped by amplified femtosecond lasers. An open-aperture Z-scan measurement performed on an n-doped InGaAs thin film using such terahertz source shows a nonlinear increase in the terahertz transmission of about 2.2 times. Our findings demonstrate the potential of this terahertz generation scheme, based on ytterbium laser technology, as a simple and efficient alternative to the existing intense table-top terahertz sources. In particular, we show that it can be readily used to explore nonlinear effects at terahertz frequencies.

Influence of Process Parameters on the Mechanical Properties of Laser Deposited Ti-6Al-4V Alloy. Taguchi and Response Surface Model Approach

Titanium alloys have found increased applications in marine, medical, military, aerospace, and automobile industries because of their light weight, good fatigue strength and corrosion-resistance properties. The present study is focused on establishing the effect of process parameters on the coatings performance of Ti-6Al-4V alloy (Grade 5) by optimizing the mechanical properties using Taguchi method and Response Surface Model (RSM). Laser surface alloying was performed using a 3-kW continuous wave (CW) Ytterbium Laser System (YLS) controlled by a KUKA robot which controls the movement of the nozzle head and emitting a Gaussian beam at 1064 nm. The relationships between the input laser-alloying parameters (laser power, scanning speed and powder feed rate) and the process responses (hardness, yield strength and tensile strength) were investigated. The L4 orthogonal array based on design of experiments was used to conduct the experiments. The degree of influence of each process parameter on individual performance characteristic was analyzed from the experimental results obtained using both Taguchi method and RSM. Analysis of variance (ANOVA) demonstrated the significant and non-significant parameters as well as validity of predicted model. The laser power and scanning speed were identified as the most influential process parameters on the mechanical properties of the laser deposited Ti-6Al-4V alloy. The developed model corresponds with the experimental results with error of 0.01 %.

Effects of Cooling Rate and Silicon Content on Microstructure and Mechanical Properties of Laser Deposited Ti-6Al-4V Alloy

The growth in the use of titanium alloy components in marine industries, aerospace, medical apparatus and power machinery has increased because of its good properties. Some detriments such as low hardness, poor thermal stability and poor tribological properties has however limits its wide range application to the industries. This has led to a search for techniques to improve the surface of Ti-6Al-4V alloy to enhance longevity in service. Laser deposition is one of the feasible techniques to modify the surface of titanium alloy which involves addition of reinforcements to improve properties without changing the bulk properties while optimizing the parameters.Hence, laser surface modification by incorporating chemical barrier coatings can be very beneficial and this lead to investigation aimed at enhancing the surface properties of Ti-6Al-4V alloy by incorporating Al-Si-Ti coatings. For this purpose, a 3-kW continuous wave ytterbium laser system attached to a KUKA robot which controls the movement during the alloying process was utilized to deposit coatings with stoichiometry Al-12Si-3Ti and Al-17Si-5Ti. The alloyed surfaces were investigated in terms of its mechanical properties as function of the laser processing conditions. Hardness measurements were done using a Vickers micro-hardness tester. The microstructures of the coated and uncoated samples were characterized by optical and scanning electron microscopy. The optimum performances were obtained for an alloy composition of Al-17Si-5Ti, at laser power of 900 W and coating speed of 1.2 m/min. Its performance enhancement compared to the unprotected substrate comprised a significant increase in hardness from 296 to 689 HV which translates to 57.04% in hardness values above that of the substrate.The enhanced increase in hardness of the coating can be traced to the presence of silicon and the various hard titanium aluminides intermetallic (TiAl, TiAl3, and Ti3Al) phasese.

Effects of rapid solidification on the microstructure and surface analyses of laser-deposited Al-Sn coatings on AISI 1015 steel

Corrosion and wear phenomenon has been responsible for the gradual deterioration of components in industrial plants. This deterioration of components results in loss of plant efficiency, total shutdown and aggressive damage in a number of industries. Hence, surface modification and coating technique with enhanced surface properties is desirable. The study was designed to investigate the enhancement in the corrosion, hardness and wear properties of Al-Sn binary coatings on AISI 1015 steel by laser alloying technique using ytterbium laser system (YLS). A laser power of 1000 W, scanning speeds of 0.6 and 0.8 m/min, and alloy compositions of Al-75Sn, Al-50Sn and Al-25Sn were used in this study. Decrease in Sn content from 75 to 25% at different laser processing conditions resulted in improved properties. The enhanced properties were obtained at 75Al-25Sn alloy at laser power of 1000 W and speeds of 0.6 and 0.8 m/min. At optimum composition and speed of 0.8 m/min, there was enhancement of 53.63% in microhardness. At scanning speed of 0.6 m/min, 75Al-25Sn alloy exhibited the highest polarization resistance, R p, (1.06 × 108 Ω cm2); lowest corrosion current density, I corr, (3.12 × 10−7 A/cm2); and lowest corrosion rate, C r, (0.00363 mm/year) in 3.65 wt% NaCl solution. In addendum, significant reduction in wear volume loss of 75Al-25Sn alloy at 0.8 m/min was attributed to excellent wear resistance performance due to metastable intermetallic phases. This research has established the enhanced surface properties of laser alloyed Al-Sn binary coatings on AISI steel for engineering applications.

Effect of process parameters on the microstructure, hardness and wear resistance properties of Zn-Sn-Ti coatings on AISI 1015 steel: laser alloying technique

The deterioration of materials during industrial application poses a serious threat to the materials structural integrity. A material's susceptibility to wear and surface damage can be reduced by alteration of its surface chemistry, morphology and crystal structure which plays an important role in optimising a material's performance for a given application. The aim of the research was to investigate the enhancement in the microstructure and wear property of Zn-Sn-Ti ternary coatings on AISI 1015 steel by laser alloying technique using Ytterbium laser system (YLS). A laser power of 750-900 W, scanning speeds of 0.6 and 0.8 m/min, and alloy compositions of 25Zn-25Sn-50Ti and 20Zn-20Sn-60Ti were used in this study. At optimum composition of 20Zn-20Sn-60Ti and speed of 0.8 m/min, there was enhancement of 24% in wear resistance performance which was attributed to metastable intermetallic phases. The coatings were free of cracks with homogeneous and refined microstructures and good adhesion to the substrate. The response surface model (RSM) used authenticates reasonably with the experimental results.

Effect of Process Parameters on the Microstructure, Hardness and Wear Resistance Properties of Zn-Sn-Ti Coatings on AISI 1015 Steel: Laser Alloying Technique

The deterioration of materials during industrial application poses a serious threat to the materials structural integrity. A material's susceptibility to wear and surface damage can be reduced by alteration of its surface chemistry, morphology and crystal structure which plays an important role in optimising a material's performance for a given application. The aim of the research was to investigate the enhancement in the microstructure and wear property of Zn-Sn-Ti ternary coatings on AISI 1015 steel by laser alloying technique using Ytterbium laser system (YLS). A laser power of 750-900 W, scanning speeds of 0.6 and 0.8 m/min, and alloy compositions of 25Zn-25Sn-50Ti and 20Zn-20Sn-60Ti were used in this study. At optimum composition of 20Zn-20Sn-60Ti and speed of 0.8 m/min, there was enhancement of 24% in wear resistance performance which was attributed to metastable intermetallic phases. The coatings were free of cracks with homogeneous and refined microstructures and good adhesion to the substrate. The response surface model (RSM) used authenticates reasonably with the experimental results.

Structure and properties of ultra fine grained aluminium alloys after laser surface treatment

The presented investigation results concern the influence of laser heat treatment on the structure and properties of aluminium alloys that underwent severe plastic deformation using the equal channel angular pressing method. The initial stage of this study aimed at determining the possibility of improving the mechanical properties of core material using the severe plastic deformation process method and the subsequent partial recrystallization process that allows obtaining equivalent ductility and grain refinement. The next stage involving investigating the surface modification of the fine grained alloy by remelting and feeding silicon carbide powder into the molten material and to end solidification. To modify the surface layer of aluminium alloy, the Ytterbium Laser System YLS‐4000 has been used, with the applied power of the laser beam in the range of 1.2 kW and 2.0 kW. The linear laser scan rate was 0.4 m/min. Results of the conducted treatments a core material with better mechanical properties, in comparison to initial state, was obtained whereas laser surface treatment allows to obtain composite surface with increased hardness and enhanced wear resistance when compared to substrate material.

Tribocorrosion Response of Laser Clad TiNiZrO<sub>2</sub> Composite Coatings on Ti6Al4V

The design of tribocorrosion resistant composite on Ti6Al4V alloy by laser surface cladding of admixed metal-ceramic powder was successfully achieved using a 2 kW CW ytterbium laser system (YLS). The effects of TiNiZrO2 addition on the tribocorrosion properties of the synthesized composite coatings were investigated in 1 M H2SO4 solution using open circuit potential and potentiodynamic polarization techniques. The experimental results showed that TiNiZrO2 refined the microstructure to flower-like structure. A strong metallurgical bond was obtained between the coatings and the Ti6Al4V alloy substrate with inter-columnar widmansttaten α΄ grains at the interface. There was a significant increase in surface microindentation hardness values of the clad layers. Also, the presence of zirconia shifted the tribocorrosion potential to more noble values and significantly enhanced the tribocorrosion resistance of the composites.

Parameters of Laser Welding and their Influence of Weld Seam

Lap joints are most used joints in automotive industry. These types of welds are usually created by spot welding, but new technologies who came to automotive industry considerably do weld process faster. Paper deals with laser welding parameters and their influence of weld seams. The parameters of welding are readjusting according to shape of weld, impurities of surface and gap. Steel S500MC with thickness of 1.0 and 2.2 mm was used as the base material. For welding was used fiber laser Ytterbium Laser System YLS with power of 6000 watt from IPG Company. Research was oriented on changing weld parameters and their influence of welds quality. It was found that butt welding joints are sensitive to gap and the gap tolerances which in turn is dependent on material thickness, beam diameter, welding speed and beam quality.

Improving the tribocorrosion resistance of Ti6Al4V surface by laser surface cladding with TiNiZrO2 composite coating

Ti6Al4V alloy was laser cladded with titanium, nickel and zirconia powders in different ratio using a 2kW CW ytterbium laser system (YLS). The microstructures of the cladded layers were examined using field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). Corrosion and tribocorrosion tests were performed on the cladded surface in 1M H2SO4 solution. The microstructure revealed the transformation from a dense dendritic structure in TiNi coating to a flower-like structure observed in TiNiZrO2 cladded layers. There was a significant increase in surface microindentation hardness values of the cladded layers due to the present of hard phase ZrO2 particles. The results obtained show that addition of ZrO2 improves the corrosion resistance property of TiNi coating but decrease the tribocorrosion resistance property. The surface hardening effect induced by ZrO2 addition, combination of high hardness of Ti2Ni phase could be responsible for the mechanical degradation and chemical wear under sliding conditions.

Tribocorrosion behaviour of laser cladded biomedical grade titanium alloy

The tribocorrosion behaviour of laser cladded Ti6Al4V sliding against alumina ball in 3.5% NaCl has been assessed. Commercially pure (CP) Ti particles were laser cladded on Ti6Al4V using ytterbium laser system (YLS). The tribocorrosion behaviour of Ti6Al4V before and after treatment was investigated in 3.5% NaCl (pH = 6.24) and modified 3.5% NaCl (pH = 4) solutions using a pin‐on‐disk tribometer with integrated potentiostat. Potentiodynamic polarization curves indicated that the corrosion potentials of cladded Ti6Al4V decreased compared to that of the uncladded samples. Additionally, the corrosion current densities of cladded Ti6Al4V decreased significantly in both electrolytes investigated. The tribocorrosion behaviour of cladded Ti6Al4V did not change significantly. The wear depth of cladded Ti6Al4V decreased significantly in modified 3.5% NaCl whilst remaining unchanged in 3.5% NaCl. The coefficient of friction (COF) increased with time in Ti6Al4V whilst that of cladded sample decreased marginally with time in both electrolytes.

Efficient compression of the femtosecond pulses of an ytterbium laser in a gas-filled capillary

A 290-fs radiation pulse of an ytterbium laser system with a central wavelength of 1028 nm and an energy of 145 μJ was compressed to a 27-fs pulse with an energy of 75 μJ. The compression was realised on the basis of the effect of pulse spectrum broadening in a xenon-filled glass capillary for a pulse repetition rate of 3kHz.

Two-photon Polymerization as Method for the Fabrication of Large Scale Biomedical Scaffold Applications

Two-photon polymerization (2PP) using ultra-short laser pulses is a well-known methodology for the 3D free-form fabrication of optical devices with resolutions down to 100 nm. However, the structure dimensions have been restricted to quite small sizes, mainly due to limitations of the focussing optics and due to very long fabrication times. Therefore, the largescale fabrication of biomedical scaffold structures with dimensions in the mm-range still remains challenging. Using a diode-pumped Ytterbium laser system emitting 325 fs laser pulses at 515 nm after second harmonic generation we are able to write arbitrary 3D structures in inorganic-organic hybrid polymers (ORMOCERs). Our setup is able to produce structures with mm extension normal to the substrate at a structural resolution of a few microns. In particular, a 3D porous inner structure can be provided, which is required for three-dimensional cell growth to support cell adhesion and proliferation. Scaffold structures were produced with different parameters, and they were characterized in order to demonstrate their potential concerning resolution and scaffold quality. It is found that not only the experimental setup, but also the substrate material plays an important role for the scaffold fabrication process and structural quality.