Mise en œuvre d'un alliage "invar" Fe-Ni par Laser Beam Melting

Abstract

The technique of selective laser melting (SLM), developed in the late 20th century knows significant developments at present times. This technique, consisting of melting powder by successive layers, has the advantage of making extremely complex shapes, unachievable by traditional techniques. The use of different types of metal materials broadens its scope. The purpose of this work is the implementation of an Invar alloy by laser melting selective. Our main objective was to know the influence of each stage of heat treatment on microstructure and properties of Invar 36. Invar is an iron-nickel alloy with 36% Ni, which has the distinction of having a very low coefficient of thermal expansion in a wide temperature range around room temperature. This feature presents a major technological interest. After a brief explanation about the art on Invar, Invar effect and the SLM process, I will then present the pieces Invar manufactured by SLM for which a characterization of the microstructure was performed before and after heat treatment. The microstructural characterizations were performed with an optical microscope and scanning electron, and through Vickers hardness measurements and expansion. The results showed that the heat treatment does not significantly affect the microstructure and hardness of samples. The porosity rate decreases from the outside towards the inside of the building board and the thermal expansion coefficient of the alloys varies very little after heat treatment. In order to make a "preliminary validation and unoptimized" of the fabrication technique SLM Invar, a comparison is made between the parts produced by SLM and an extruded rod of Invar. An important discussion is then proposed on the influence of various parameters such as chemical composition, method of preparation and heat treatment on the properties and microstructure expansion.