Effect Of Laser Melting Research Articles

Effect of simultaneous application of ultrasonic vibrations during laser surface melting on electrochemical properties of 2024 aluminum alloy

In the present investigation, effect of laser melting with and without simultaneous application of ultrasonic vibrations on electrochemical properties of 2024 aluminum alloy is investigated. The electrochemical behavior of the laser melted specimens was studied using open-circuit and potentiodynamic polarization measurements. Subsequently, investigation of the corrosion films was performed using scanning electron microscopy. It was observed that the laser melted specimens exhibited significant improvement in open circuit potential (both with and without simultaneous ultrasonic vibration application). The open circuit potential of the laser melted specimen without ultrasonic vibrations was observed to be more stable compared to the laser melted specimen with ultrasonic vibrations. It was observed that the corrosion mechanism undergoes a transition from pitting to uniform corrosion in the laser treated specimen, particularly in the laser melted specimen without ultrasonic vibrations. However, the extensive agitations due to ultrasonic vibrations in the melt pool appear to restrict Cu migration to grain boundaries that result in porous and relatively inefficient passive layer formation in laser processed samples with application of ultrasonic vibrations. This behavior was also observed in the potentiodynamic polarization studies that showed that the laser melted specimen without ultrasonic vibrations exhibited lower corrosion current and corrosion rate compared to the laser melted specimen with ultrasonic vibrations as well as the as received substrate. Copyright © 2017 VBRI Press.

Effects of laser melting+remelting on interfacial macrosegregation and resulting microstructure and microhardness of laser additive manufactured H13/IN625 bimetals

Macrosegregation at the interface in Multi-Material (MM) structures fabricated by Selective Laser Melting (SLM) has evidenced deleterious effects on interfacial bonding reliability, but its fundamental understanding is less revealed. Therefore, this work vertically prepared MM parts of H13 tool steel and IN625 superalloy by SLM, as an example, to explore the interfacial macrosegregation mechanism. According to the mechanism, a liquid layer of unmixed H13 can exist at the molten pool bottom due to the no-slip boundary condition in fluid mechanics and solidifies as an H13 macrosegregation beach. Considering the higher liquidus temperature of H13 (1483 °C) than IN625 (1300 °C), a region cooler than the H13 solidification temperature exists within the IN625 molten pool; therefore, when the melted but unmixed H13 liquid is entrained into the cooler region by fluid flows, it can solidify quickly, forming H13 macrosegregation peninsulas/islands. The laser melting+remelting strategy developed to mitigate interfacial macrosegregation reveals its significant contribution to efficient migration of H13 into IN625 molten pools in a layer-by-layer manner, forming a broad interface. As the direct reflection of interfacial macrosegregation, the microstructure experiences a cellular-columnar-cellular transition across the H13/IN625 interface. Even a peninsula with H13 microstructural features is observed in an IN625 molten pool, verifying the rapid solidification of intruded H13 in IN625. Finally, the microhardness values with varying standard deviations across the interface successfully evaluate the interfacial macrosegregation on a macro-scale. These results can provide theoretical support to mitigate interfacial macrosegregation and benefit the development of MM structures with good interfacial bonding reliability by SLM.

Enhancing the (FeMnCrNiCo + TiC) cladding layer by in-situ laser remelting

ABSTRACT In this study, the (FeMnCrNiCo + 20%TiC) laser cladding layer was re-treated through multiple-pass in-situ laser remelting. Optical microscopy, scanning electron microscopy, and X-ray diffraction were used to analyse the evolution of microstructures and phases before and after the in-situ laser remelting processes. The micro-hardness and wear resistance of the composite coatings were systematically investigated using micro-hardness and abrasion. Results show that in-situ laser remelting decreased the dilution rate. The thermal effect of laser melting and the Maragni action in the liquid coating metal enabled the large-sized and loosened ceramic particles to remelt into the cladding layers. As a result, the ceramic particles in the cladding layers after in-situ laser remelting were modified considerably in terms of their spherification rate, dimension uniformity, and particle distribution. The weak spots caused by stress on the surfaces of the cladding layers were reduced, and accordingly the wear resistances improved.

激光熔凝对AerMet100钢显微组织及性能的影响

激光熔凝对AerMet100钢显微组织及性能的影响

Effect of laser melting on plasma sprayed WC-12 wt.%Co coatings

Tungsten carbide powder with 12% Co was deposited on AISI 321 stainless steel substrate by air plasma spraying. The coating was produced at 130mm standoff distance. The coated samples were melted using a CO2 laser with an inert gas shroud. Four different laser speeds from 100mm/min to 250mm/min were used to melt the coatings. After laser melting the treated surfaces were characterized and compared with as sprayed surfaces. It was observed that the laser melting process produced defect free surfaces. The results showed that the thicknesses of the melted surfaces and wear resistance varied as a function of laser speed.

Synthesis of Al0.5CoCrCuFeNi and Al0.5CoCrFeMnNi High-Entropy Alloys by Laser Melting

High-entropy alloys (HEAs) are a blend of 5+ metallic elements that can form solid solution disordered structures. Two HEAs were synthesized using laser melting in an argon atmosphere. The relatively well-studied Al0.5CoCrCuFeNi alloy was first produced to establish the feasibility of laser melting. Manganese was then substituted for copper to potentially lower both cost and density, producing a novel Al0.5CoCrFeMnNi alloy system. These samples were analyzed with XRD, SEM, EDS, and Vickers microhardness to determine the effects of the manganese substitution, as well as the effects of laser melting in comparison to the more traditional arc melting.

Effect of drug loading on laser modification of polymer biodegradation

Biodegradable polymer is promising in drug delivery applications, while its degradation characteristics include an undesirably slow induction period of drug release. Through modifying polymer surface crystallinity, laser melting accelerates initial polymer degradation and potentially shortens the induction period of drug release. Effect of drug loading on laser modification of polymer degradation is investigated in this study. With a higher drug concentration, effect of laser melting on crystallinity and degradation modification is reduced. This is attributed to the fact that laser energy is partly absorbed by drug molecules, and less energy is available to melt the polymer matrix.

Laser polishing of niobium for application to superconducting radio frequency cavities

Superconducting radio frequency niobium cavities are at the heart of an increasing number of particle accelerators. Their performance is dominated by a several nanometer thick layer at the interior surface. Maximizing the smoothness of this surface is critical, and aggressive chemical treatments are now employed to this end. The authors describe laser-induced surface melting as an alternative “greener” approach. Selection of laser parameters guided by modeling achieved melting that reduced the surface roughness from the fabrication process. The resulting topography was examined by scanning electron microscope and atomic force microscope (AFM). Plots of power spectral density computed from the AFM data give further insight into the effect of laser melting on the topography of the mechanically polished (only) niobium.

Effect of laser melting on plasma-sprayed aluminum oxide coatings reinforced with carbon nanotubes

The effect of laser melting on the microstructure and mechanical properties of plasma-sprayed aluminum oxide composite coating reinforced with 4 wt% multi-walled carbon nanotubes (CNTs) is reported. Laser-melted layer consists of dense, coarse columnar microstructure which is significantly different from plasma-sprayed coating that consists of splats and porosity. CNTs retained their original cylindrical graphitic structure after undergoing laser irradiation. Three dimensional heat flow model has been developed to estimate temperature variation in the laser-melted composite layer. Laser-melted layers show an increase in the microhardness at the expanse of degradation of fracture toughness. Nanoindentation study indicates an increase in the elastic modulus and yield strength of the laser-melted layer which is attributed to dense microstructure with absence of weak-bonding splats and porosity.

レーザ多重熱サイクルによる金属表面の微細化に関する研究(S55-1 レーザ加工(1),S55 レーザ加工)

The effect of laser melting with multiple thermal cycles on grain refining of carbon steels and aluminum alloys ahs been investigated using 2.4kW CO2 laser and beam rotating device. Phase transformation from liquid to solid and from solid to liquid can be promoted in the metal during the laser processing. The nucleation and growth of solid crystal is suppressed by rapid thermal cycle. Therefore, grain refining is available in laser remelting. of alloys. The effect of solidification range of alloys was also investigated. As a result, the grain size (DAS) was decreased by rapid thermal cycle during laser melting of metal surface. The mechanical properties like wear resistance and hardness were estimated.

Microstructure and properties of laser treated arc sprayed and plasma sprayed coatings

The effect of laser melting on the microstructure, porosity, chemical homogeneity of nickel based alloy plasma sprayed and (Fe–Cr–B)+Al based electric arc sprayed coatings has been investigated. Laser melting markedly improves coating microstructure and density, and much better chemical homogeneity is obtained. Laser treatment of coatings was carried out with the help of a CW CO2 laser (λ=10.6μm) using the graphite based antireflection coating. The results demonstrate an improvement of mechanical and corrosion properties of coatings.

Effects of Laser Surface Melting on Structure Character and Erosion Resistance of Plasma Sprayed Ceramic Coatings

ABSTRACTIn this work the effects of laser melting on the micro-morphology, structures and solid particle erosion behaviors of plasma spray alumina, alumina-titania and zirconia coatings have been studied. The results have indicated that laser melting has modified the micro-mophologies and structures of coatings, eliminated the porosity of sprayed coatings and increased the erosion resistance of ceramic coatings. The erosion mechanisms of ceramic coatings have been investigated.