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Metal cladding

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Ce travail de fin d'études consiste en l'étude de la comparaison entre deux logiciels éléments finis: Lagamine et le code_aster dans le cadre d'un processus de fabrication additive (FA) appelé Le laser cladding. 

Ce procédé de modélisation comprendra une modélisation de la géométrie et du maillage, de la source de chaleur et des autres conditions limites à appliquer, du matériau ainsi que des lois thermiques correspondantes, du procédé d'activation des éléments, et ce, de manière fidèle aux conditions expérimentales.

Ce travail constitue un premier pas vers le développement d'un modèle thermo-mécanique complet.

cladding --- Ingénierie, informatique & technologie > Ingénierie civile

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Aluminum alloys. --- Metal cladding. --- Corrosion resistant alloys. --- Corrosion resistant materials.

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Abstract 
Titanium is the fourth most abundant structural metal in the world. It is known to have a high strength, light weight, good formability and high corrosion resistance. Due to these properties, Titanium and its alloys are used in many industries, such as aerospace and automobile. Note that due to its high price, one can find Ti6Al4V in demanding applications. 
This master thesis defines quantitatively predicting of the microstructure of a titanium alloy, Ti6Al4V, worked with laser cladding process. The main goal is to define the proper phase transformation conditions that lead to reliable phase predictions. 
Outcomes are checked from the results obtained by two experimental observations in laser cladding process for the Ti6Al4V. Both studies obtained qualitative results according to the phases that formed the microstructure of the alloy and the hardness value of three different points located in the deposits. As a first reference, H.S. Tran used Constant Track Length building strategy. The second study has been made by MMS team at University of Liège, but it has not been published yet. They used a Decrease Track Length building strategy. The initial experimental work was done by H.Paydas .
This master thesis is based on the implementation of a Fortran code that defines the phase transformations of Ti6Al4V. Inside the code, the thermal conditions and the equations with their parameters are defined. The project was based on Crespo’s model that calculates the phase transformation kinetics of this titanium alloy. After applying the same model, some differences have been made in order to achieve the desired results according to the improvement works done by H.S Tran and MMS team. 
This document presents a flow work starting with the basic theoretical background about Additive Manufacturing, Titanium and its alloys. After, Ti6Al4V is presented: its chemical composition, the different phases that can describe its microstructure and the equations that define the transformations from one phase to the other. The parameters and conditions defining those equations are determined and compared with previous literature, concretely with Crespo. Finally the results and conclusions are presented. 
Keywords: Laser Cladding (LC), Ti6Al4V, microstructure, thermal history, Fortran.

Laser Cladding (LC), Ti6Al4V, microstructure, thermal history, Fortran. --- Ingénierie, informatique & technologie > Science des matériaux & ingénierie

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In this master thesis, a gradient composition material was developed and characterized using direct energy deposition additive manufacturing. The goal was to enhance the mechanical properties of a pinion located in the deployment mechanism of slats produced by Sonaca. 
The materials selection resulted in choosing martensitic and ferritic steels.

Powders from Pometon and Sandvik were characterized by means of an optical microscope, differential thermal analysis, scanning electron microscope, gas pycnometer and granulometry. Pometon powders were found to contain chromium oxides while Sandvik powders showed good features.

Deposits were printed with different laser parameters. The ferritic zones of the sample exhibited in-situ oxides that were avoided by increasing the incident energy. The martensitic zones presented no porosities nor cracks. The gradient structure showed up to have no added value due to a lack of corrosion resistance as well as a hardness similar to the martensitic zone. Due to the COVID-19 outbreak, characterization of deposits was not completed.

The reference part was characterized and its properties were compared to those of the deposits. The reference part had a better surface hardness but a significantly lower corrosion resistance. Additional characterization means are required to draw conclusions on the interest of deposits compared to the currently used material and surface treatments.

Additive manufacturing, metallic materials, cladding, martensite, ferrite, hardness --- Ingénierie, informatique & technologie > Science des matériaux & ingénierie