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In this work, fabricated samples of additively manufactured 420 stainless steel (420SS) via laser powder bed fusion (LPBF) process were analyzed. The microstructural features, grain morphology, crystallographic texture, phase composition, and tensile properties were evaluated for both as-printed and heat-treated conditions. The as-printed condition exhibits a yield strength of 1083 MPa and a tensile elongation of 21.2%. Microstructure analysis revealed that its comparable ductility is due to the presence of 15.2 % of retained austenite. After the successive heat treatment procedure, the yield strength improved significantly to 1388 MPa while decreasing the tensile elongation to 12.4 %. The yield strength obtained in the heat-treated condition was superior to previously reported literature values of precipitation hardening stainless steels fabricated by LPBF, and 420SS fabricated using different additive manufacturing processes. This improvement in yield strength is attributed to the coarsening of martensite laths and needles, elimination of retained austenite phase, and the carbide precipitation of 1.9 vol. % in the microstructure. The results in this work proved that the tensile properties and microstructure were greatly influenced by laser parameters and can be tailored accordingly using different heat treatment techniques.

Hydrogels are smart materials that have the capability to absorb water by over five hundred times their own weight and showed various applications in biomedical field, including drug delivery systems, tissue engineering and wound healing. In this study, the fabrication of polyvinyl alcohol hydrogels reinforced with cellulose and silica nanoparticles was investigated for possible use in wound healing applications. Synthesis was done through chemical cross-linking of polyvinyl alcohol and sodium borate. Results showed that mechanical properties and thermal stability of the reinforced hydrogels were improved compared to the neat hydrogel. The nanosilica-reinforced hydrogels showed antimicrobial activity and improved degree of swelling compared to the neat PVA hydrogels. Sparse growth was observed in the antimicrobial assay with Pseudomonas aeruginosa and Staphylococcus aureus. Cellulose-reinforced hydrogels showed minimal flexibility characteristic compared to the nanosilica-reinforced hydrogel samples. Moreover, it showed no antimicrobial activity against Pseudomonas aerigunosa.