Abstract
Laser metal deposition (LMD) is one of the most important laser additive manufacturing processes. It can be used to produce functional coatings, to repair damaged parts and to manufacture metal components. Ti6Al4V is one of the most commonly used titanium alloys, since it features a good balance of the mechanical properties of strength and ductility. The LMD of Ti6Al4V is attracting more and more attention from both science and engineering. The interest in processing Ti6Al4V with LMD in industry, especially in aerospace and medical branches, has been increasing in the last few years. In this paper, the state of the art for LMD of Ti6Al4V is reviewed. In the first part, the basics for Ti6Al4V, including, for example, the development history, the material properties, the applications, the crystal structure, the heat treatment and the mechanical properties, are introduced. In the second part, the main emphasis is on state of the art for LMD of Ti6Al4V. Initially, the process parameters of the current state of the art in the last years and their effects are summarized. After that, the typical microstructure after LMD is discussed. Then, the conducted heat treatment methods and the achievable mechanical properties are presented. In the end, some of the existing, current challenges are mentioned, and the possible research directions for the future are proposed.
Highlights
Laser metal deposition (LMD) is an additive manufacturing process, by which a laser beam is used as the energy source to form a melt pool on the surface of a metallic substrate into which metal powder is injected by a gas stream and melted
Heat treatments are performed on Ti6Al4V in order to modify its microstructure, to increase strength or ductility, to reduce the residual stress and/or to optimize the fatigue strength or high-temperature strength [19]
The first commonly used heat treatment is the solution treatment followed by quenching and aging, through which the strength of Ti6Al4V is increased by turning β phases into α martensite phases [13]
Summary
Laser metal deposition (LMD) is an additive manufacturing process, by which a laser beam is used as the energy source to form a melt pool on the surface of a metallic substrate into which metal powder is injected by a gas stream and melted. LMD has a variety of advantages over other deposition processes; for example, the lower heat input and the related smaller heat affected zone, by which the deformation can be significantly reduced and the heat influence on the surface of the substrate can be minimized Another advantage is the higher cooling rate, which leads to a finer microstructure, and this is generally positive for the material performance [3]. The state of the art for LMD of Ti6Al4V will be based on the reviewing of the scientific work conducted in the last few years In this regard, the process parameters, macrostructure and microstructure, heat treatment methods and the achievable mechanical properties, are the focal points
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