Improvement of surface finishing and corrosion resistance of prototypes produced by direct metal laser sintering

Using the prototyping technology it is possible to obtain in short production time components like mould for production of polymeric parts. In this paper the direct metal laser sintering technology is utilised to produce a benchmark to evaluate some limits and the problems of this technology concerning the surface finish. Several surface treatments are carried out to reduce surface roughness. The most promising are the grinding and emery polishing, which produce an Ra lower than 1 μm. Following the deposition of some coatings is considered to improve the quality of the surface finishing and to guarantee the corrosion resistance of prototyped components. CrN/NbN layers, PTFE-based coating and electroless nickel coatings with and without SiC and PTFE particles are considered. The nickel coating, applied after shot peening and polishing, shows the best performance because of the coatings show an uniform thickness and guarantee a good corrosion protection. Finally, 500 polymeric pieces are produced through polypropylene injection utilising prototyped nickel protected mould, without wear problem of mould.