Proceedings The Third World Congress on Intelligent Manufacturing Processes & Systems Cambridge, MA – June 28-30, 2000 Copyright © by PSD 2000 Page: 1 ABSTRACT The development of new metal powders for the selective laser sintering process is considered underlining the importance of an integrated approach considering powder metal technologies, the specific manufacturing process and some empirical correlations that have been found in the field. Some relevant physical parameters, flow rate, density and thermal conductivity are considered, together with some elementary thermophysical requirements of the process. The corresponding sintered body properties are presented, with in mind testing procedures in the field of sintered metals. Industrial and developing processes of powder production - divided in primary and secondary powder treatments - are reviewed, with the aim of identifying improved or tailored production routes for industrial powders for this rapid prototyping technique. Examples of applications of laboratory developed powders are given, together with the properties of the laser sintered bodies. Keywords: Rapid Prototyping, Selective Laser Sintering, Metal Powder Technologies PAPER TOPIC Rapid Prototyping 1 INTRODUCTION The technique of selective laser sintering is one of the most promising applications of the layer manufacturing technologies, and it is currently commercially available for a variety of materials Systems including most of the material classes including for instance plastics, metals and ceramics. Even in the apparently narrower field of direct metal selective laser sintering (DMSLS) conceptually many different systems with different material properties are conceivable; this paper has the aim of stimulating the discussion on the possible development of new powders for the DMSLS as it is felt that the two materials currently commercially available today are not enough representative of the wealth of different metal materials that may be found for technical applications today. Metal powders technological properties are deeply influenced by the manufacturing routes employed for their production; much more than cast and wrought metal and alloys technological properties of a metal powder are not just depending on the quantities of alloying elements. It will be then useful to consider briefly metal powder and sintered metals properties, in order to consider some possible candidate powders for development of the process. On the contrary of what one frequently reads in many different recent papers, it would be better to consider the DMSLS a “true” sintering process; there is in fact a number of loose powder sintering applications, for instance for specialized powder metallurgy applications such as bronze filters and porous electrodes, where the densification of metal powders is due only to heating effects. So DMSLS processes should be considered in the framework of the liquid phase sintering processes. As reported in one of the first technical papers on Selective Laser Sintering [Bourell et al (1992)], the main mechanism that is technically applicable is the sintering of a so called two phase powder, consisting of at least two types powders of different melting points. The low melting powder melts, the liquid wets and binds the high melting point powders. Experimental trials on single phase metal powders have generally reported negative results, with the lack of formation of solid bodies at low energy doses and, rising up the density of energy flux, the so called “balling” phenomenon, i.e. the formation of spheres of diameter comparable with the focussed laser beam. In the same paper, authors stress the technological importance of the use of a low melting phase that, on melting, gives a liquid with strongly temperature dependent viscosity, i.e. a ON THE DEVELOPMENT OF NEW METAL POWDERS FOR THE SELECTIVE LASER SINTERING PROCESS Fabio Miani miani@uniud.it DIEGM Univ. of Udine Via delle Scienze 208 I 33100 Udine Italy