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As additive manufacturing (AM), or 3D printing, continues to evolve, many challenges still plague this exciting new technology.
By remelting and re-solidifying metals in powder or wire form, each printing machine essentially becomes its own foundry. Therefore, precisely defining exact and repeatable mechanical characteristics of the uniquely printed components continues to be the major hurdle for the metallurgist (Fig. 1).
In addition, the vacuum heat treating of printed components is also evolving every day. Since additively manufactured parts display vastly different mechanical behaviors when compared to conventionally produced parts, it is logical that heat treatments associated with this process also vary. Since the majority of metallic printing processes involves high-temperature melting along with rapid cooling rates, parts typically possess extremely high internal stresses.
These inherent stresses can either be an advantage or a drawback to the design of the part. When internal stresses are detrimental to the end product, vacuum stress relieving seems to be the most prevalent and essential thermal process performed on 3D-printed parts. Other less-popular vacuum thermal processes include vacuum annealing and vacuum sintering.
Equipment Needed
As additive manufacturing continues to become more popular, the manufacturer will often contract with the commercial heat treater to perform the critical thermal processing for their jobs. The AM manufacturers continue to seek out only those facilities possessing a wide variety of vacuum furnaces. These furnaces (Fig. 2) must be equipped with diffusion pumps to attain deep vacuum levels and must exhibit extremely tight temperature uniformities (±5°F).
Since the ultimate goal of printing any 3D component is to produce a part that is "near-net shaped," the vacuum-furnace atmosphere must be pristine. Surface contamination found on finished printed titanium or a nickel-based alloy part could deem the part scrap. Therefore, manufacturers will often insist that only expensive all-metal hot-zoned vacuum furnaces be used to process their parts. Vacuum heat...