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Processing of highly reflective and high thermally conductive materials (Cu, Ag, etc.) by laser powder bed fusion (LPBF) is of increasing interest to broaden the range of materials that can be additively manufactured. However, these alloys are challenged by high reflectivity resulting in unmelted particles and porosity. This is exacerbated for in-situ alloying techniques, where divergent optical properties of blended powders further narrow the stable processing window. One possible route to improved uniformity of initial melting is through coating powders with an optically absorptive layer. In-situ alloying of Ti-Ag was chosen as a model to assess this, given the potential of Ti-Ag as a novel antimicrobial biomedical alloy, facilitating an ideal model to assess this approach. High purity Ag powder was coated with Ti via physical vapour deposition. Barriers to reliable coating were investigated, with agglomeration of particles observed at a sputtering power of 100 W. In-situ laser micro calorimetry demonstrated a significant improvement in melting performance for coated Ag powder, with continuous tracks attained at 280 W vs. 320 W for uncoated powder, and absorptivity increasing from 27 % to 45 % at 320 W incident laser power. Subsequent in-situ alloying of the Ag powder when blended with commercially pure Ti powder demonstrated that improved absorptivity allowed for more uniform densification of the blended powder bed at lower energy density (0.7 ± 1.0 vs 7.1 ± 2.0 % porosity at 133 J.m-1). Ultimately, this offers a promising route to improved alloy development via LPBF, through application of a homogeneous, relevant coating.

Infections on the surface of prosthetic implants such as hip replacements account for a quarter of all implant removals, and are frequently life-threatening. To combat this, we need new approaches to make implants more resistant to infection, working together with the normal oral or injected antibiotics used after surgery. My research is finding ways to do just this using silver, an antimicrobial that has been in use for thousands of years. By using modern metal 3D printing techniques, it's possible to introduce silver to implants in entirely new ways. Whether through weaving silver into the ordinary alloy of an implant, or introducing a second material like a silver loaded cement, the next generation of implants could be protected from bacteria whilst having the customisability available through 3D printing.