Towards an innovated methodology for manufacturing homogeneous metallic alloys by the EBM technology
Résumé
The main goal of all companies is to decrease the manufacturing cost and improving quality and properties of product. We present a new methodology innovated recently by the 3A company to manufacture homogenous titanium alloys by the EBM technology. The production cycle of a metallic part made in a vacuum chamber: preheating of powder, melting and construction of layers and then cooling of manufactured part causes naturally its aging. Indeed, the onstruction of part layers is performed with expending an important energy and scanning a wide area. Outside of the parts, the unmelted powder grains badly joined are considered very poor heat conductors. These induce deformations and defects in parts such as welling,delamination…etc. The main question was: Is it possible to reduce the area scanned by the lectron beam? One of the solutions proposed and investigated is the production of hybrid components whose envelope fused by EBM. Thus the obtained pieces are completely closed hermetically and filled with agglomerated titanium powder and then compacted with applying a heat isostatic pressing. This process eliminates the material porosity without spending a lot of energy. Mechanical tests and microstructure analysis were carried out by manufacturing two types of cylindrical specimens: with or without adding lattice structures in the core of these parts. The thickness of specimen envelope fused by the EBM is enough to be closed. The core of specimens is different: "V" for test pieces containing only the agglomerated powder, and "P" for pieces having internal lattice structures (3 to 10% of the core volume). It has been shown that the grains of both envelop and core areas are differents in form and size: lamellars (15-50μm) and round particles (10-15μm), respectively. We noted that the homogeneously of compacted powder leads to excellent mechanical properties.