Hot isostatic pressing of direct selective laser sintered metal components

A new manufacturing process combining the benefits of Selective Laser Sintering (SLS) and Hot Isostatic Pressing (HIP) has been developed to permit Rapid Prototyping of high performance metal components. The new process uses Direct Metal SLS to produce a gas impermeable HIP container from the same powdered material that will eventually compose the bulk of the part. The SLS generated capsule performs the functions of the sheet metal container in traditional HIP, but unlike a sheet metal container, the SLSed capsule becomes an integral part of the final component. Additionally, SLS can produce a capsule of far greater geometric complexity than can be achieved by sheet metal forming.; Two high performance alloys, Ti-6Al-4V and Inconel 625, were selected for use in the development of the new process. HIP maps were constructed to predict the densification rate of the two materials during HIP processing. Comparison to experimentally determined densification behavior indicated that the maps provide a useful qualitative description of densification rates; however, the accuracy of quantitative predictions was greatly enhanced by tuning key material parameters based on a limited number of experimental HIP cycles.; Microstructural characterization of SLS + HIP samples revealed two distinct regions within the components. The outer SLS processed capsule material exhibited a relatively coarse microstructure comparable to a cast, or multi-layer welded structure. No layer boundaries were discernible in the SLS material, with grains observed to grow epitaxially from previously deposited material. The microstructure of the HIP consolidated core material was similar to conventionally HIP processed powder materials, featuring a fine grain structure and preserved prior particle boundaries.; The large variation in grain size between the capsule and core materials was reflected in hardness measurements conducted on the Alloy 625 material; however, the variation in hardness was less pronounced for the Ti-6Al-4V samples. Test specimens fabricated from Ti-6Al-4V exhibited tensile strengths higher than wrought material, but with a lower ductility. The low ductility was attributed to oxygen contamination during SLS processing. The use of a high purity grade of Ti-6A1-4V and careful monitoring of the processing atmosphere should improve ductility and permit rapid prototyping of metal components with mechanical properties that meet or exceed standards set by traditional processes.