Tools and moulds repair technologies with special reference to LASER metal wire deposition

The optimization of process parameters in LASER (Light Amplification by Stimulated Emission of Radiation) Metal wire Deposition (LMwD) for Tools repair (TMRT) is vital for end-user manufacturers. It represents a crucial unsolved industrial problem because tools and dies are often: (a) complex and very expensive components; sometimes are unique and difficult to rebuild ex-novo; (b) require complex and expensive processes to produce them; originally were repaired by Gas Tungsten Arc Welding (GTAW), then by LASER, (involving both superb operator skills) and, more recently, using fully automated Computer Aided Technologies (CAX), such as Metal Additive Manufacturing (MAM) based on wire/powders fillers (all denoted as Directed Energy Deposition (DED) technologies). A brief review will clarify the technological evolution of tool repair by consolidated (manual) and advanced (automated) LASER welding technologies and how these have contributed to increasing the current state of the art on MAM. Tool repair is a multidisciplinary operation: say, technological (to develop appropriate processes aimed at repairing of the damaged region), metallurgical (to select appropriate steels and filler, to assess the repaired tool micro- and macrostructure as well and eventual defects and its mechanical performances). In this contest, i) deposit reproducibility and (ii) net shape repair are important factors. The success of a deposition repair process results from numerous metallurgical phenomena influencing the microstructure, properties and its final quality, performance, and life. The optimization of process parameters is foremost and can only be attained by optimizing the microstructure of the deposit which can be attained either automatically or manually. However, most of them are still carried out manually. Among the vast range of wire-based technologies, LMwD is currently one among the widespread technologies for tool repair, as attested by the large number of scientific publications.