Aluminum to titanium laser welding-brazing in V-shaped grooveI

Laser assisted joining of AA5754 aluminum alloy to T40 titanium with use of Al-Si filler wires was carried out. Continuous Yb:YAG laser beam was shaped into double spot tandem and defocalized to cover larger interaction zone in V shaped groove. Experimental design method was applied to study the influence of operational parameters on the tensile properties of the joints. Microstructure examination and fractography study were carried out to understand the relation between local phase content and fracture mode. Within defined window of operational parameters, statistically important factors that influenced the strength of T40 to AA5754 joints in V groove configuration were Si content in the filler metal and groove opening angle on T40 side. The best quality joint showed joint coefficient of 90% (or 200 MPa of apparent UTS). Tensile strength of the joints was found to be determined by the proportion between well-developed and under-developed reaction zones of T40/melted zone interface. The formation of 2–25 μm thick Si-rich interlayers composed by Ti5Si3 and τ2 proved to enhance the strength of brazed interface. The creation of very thin (<0.5 μm) Si-rich layers at the bottom of the groove was found not sufficient to establish mechanical continuity of the joint and thus should be avoided

Laser processing and microstructure of Al-Cu-Fe quasicrystalline coatings on Al-base materials

There is a large interest in using high power lasers for surface alloying or cladding on aluminium alloys, in order to enhance hardness and to improve wear resistance. A partly quasicrystalline surface layer (QC) (Al-Cu-Fe coating) has been obtained by laser cladding on Al-base materials. In addition to crystalline phases (Al5Fe2 and Al13Fe4, with dissolved copper), a quasicrystalline Al-Cu-Fe phase is detected. However, crystallization of this quasicrystalline phase occurs during isothermal heat treatment at 525°C. A mechanism is proposed for the solidification process resulting from laser cladding

Injection coaxiale de poudres sous faisceau laser pour la réalisation de revêtements : problèmes physiques associés

Laser leading is an attractive technique for surface treatment ; by injecting an appropriated powder into the laser beam, various coatings can be achieved : metallic, ceramic or metal matrix composites (MMC), on many substrates. In the present work, a physical analysis of the different phenomena occurring during the powder-laser interaction is reported, especially the energy absorption and the resulting temperature evolution. An experimental agreement is observed with experimental results obtained in MMC coatings, manufactured by using a coaxial nozzle.La technique d'injection de poudre sous un faisceau laser est une technique de traitement de surface qui permet la réalisation de revêtements métalliques, céramiques, composites à matrice métallique (CMM), ..., sur les matériaux les plus divers. Dans cette étude, nous analysons les phénomènes physiques intervenant lors de l'interaction laser-poudre et conduisant à l'absorption de l'énergie et donc à une évolution thermique. Pour valider notre modélisation simplifiée, différents revêtements, notamment CMM, sont réalisés à l'aide d'une buse coaxiale : l'accord est satisfaisant

Microstructure and mechanical properties of some metal matrix composites coatings by laser cladding

During the last decade, many studies have been devoted to metal matrix composites (MMC), consisting of hard ceramic materials embedded in a metallic substrate. The metallic matrix provides the necessary ductility, whilst the hard phase provides the high hardness, the high Young modulus and the good wear resistance. Laser cladding can be used to elaborate such MMC ; by adjusting laser power and interaction time, it is possible to melt the metallic elements without affecting the hard phases (oxides, carbides.). The present work deals with the elaboration and the characterization of MMC coatings on different substrates (copper- or iron-base materials). Metallic matrix is constitued by a nickel base material and tungsten carbides are used as hard particles

Thermal field in a cylindrical wire getting a laser supported material cladding

This work presents the thermal field computation of a wire getting a laser supported material cladding. We present two complementary models, based on finite volume approaches. First, we present a one dimensional model in which moving of the wire is integrated by mean of an advection term in the heat diffusion equation. It gives the mean temperature variation along the wire An analytical solution of this problem is also given. Secondly, a three-dimensional model gives the complete thermal field. These two models are confronted with experiments. The result of the first one is compared to a maximum mean temperature measuring. The second is validated by comparison with microphotography of the melted zone, and in-section micro-hardness measurements

Etude d'un revêtement d'acier inoxydable Z 2 CND 18-12 réalisé sur un acier doux, sous irradiation laser avec injection de poudre coaxiale au faisceau

Le présent travail traite du dépôt d'acier inoxydable austénitique de type AISI 316 L sur acier doux par projection de poudre sous faisceau laser et de la caractérisation du revêtement élaboré. Les revêtements obtenus par cette technique sont de bonne qualité, exempts de fissures, avec peu de porosités et parfaitement adhérents au substrat. Leur microstructure très fine est dendritique ou cellulaire. La structure est apparue majoritairement austénitique, mais avec présence non négligeable de ferrite [MATH] localisée aux joints de grains d'austénite. La résistance à la corrosion, tant généralisée que par piqûre en solutions salines aqueuses, s'est avérée excellente

Austenitic stainless steels layers deposited by laser cladding on a mild steel : realization and characterization

The present work reports on 18-10 (AISI 304 grade) and 18-12-Mo (AISI 316 grade) stainless steel coatings produced by laser powder cladding technique. Clad layers of uniform thicknesses have been produced through partially overlapping single cladding tracks. The clad layers thus obtained show excellent adherence, few porosities and good chemical homogeneity. The microstructure is dendritic or most often cellular. The 304 clad layers are free of cracks and have a structure mainly austenitic with a certain amount of [MATH]. The 316 clad layers show always cracks and their structure is almost fully austenitic. Primary solidification of [MATH] phase seems thus favourable to prevent hot cracking of the austenitic stainless steels layers. The corrosion resistance of the crack-free 304 clad layers has been tested in various saline media. In every case, the coatings exhibit a very good uniform corrosion resistance

The numerical challenges in multiphysical modeling of laser welding with arbitrary Lagrangian-Eulerian method

International audienceThe interaction of high power laser beam with metallic materials produces a number of interconnected phenomena that represent a serious challenge for numerical modeling, especially for creation of auto-consistent models. Additional difficulty consists in lack of data on materials properties at the temperatures superior to their melting point. The present work summarizes the numerical challenges in creation and validation of free-surface models using ALE moving mesh coupled with heat transfer equation and Navier-Stokes fluid flow