<p class="MsoNormal" style="text-align: justify">This study investigates the application of electroless nickel deposition on additively manufactured stainless steel samples. Current additive manufacturing (AM) technologies produce metal components with a rough surface and high sensitivity towards corrosive environments. This paper discusses the advancement in surface roughness reduction of the internal and external surface of complex shapes and geometries of additively manufactured components. However, surface finishing alone is not sufficient to make corrosion-sensitive additively manufactured metal components.&nbsp; Also, an additive manufacturing component that is expected to encounter mechanical wear damages needs wear-resistant coating like nickel (Ni). This paper demonstrates our research in producing electroless nickel (Ni) coating on the surface of 316L stainless steel components after the surface finishing treatment. This study analyzes chempolishing (CP) and Electropolish (EP) surface finishing techniques for post-process of the AM stainless steel components. CP is a pure chemical process in which the solution continually anodized the sample where oxidation-reduction occurs. CP has a great advantage in creating uniform, smooth surfaces regardless of size or part geometry. EP is an electrochemical process that requires an electric current for polishing to happen. EP creates an extremely smooth surface, which reduces the surface roughness to the sub-micrometer level. We found out EP and CP reduced the arithmetical mean height (Ra) of the surface roughness by ~80%. After surface finishing, we applied electroless Ni coating. Electroless nickel coating provides a barrier of corrosion shield to steel. Electroless nickel coating can be applied with negligible compressive stress making this process suitable for coating complex shapes of AM components. Electroless nickel plating is a method of alloy treatment designed to increase manufactured component's hardness and surface resistance to the unrelenting environment. The electroless nickel plating process is more straightforward than its counterpart electroplating. We investigated nickel deposition on EP, CP, and as-built AM components using electroless nickel solutions. For this study, we use low-phosphorus (2-5% P), medium-phosphorus (6-9% P) and high-phosphorus (10-13% P). These Ni deposition experiments were optimized using the L9 Taguchi design of experiments (TDOE) compromises the prosperous content in the solution, surface finish, plane of the geometry, and bath temperature. The pre-and post-processed surface of the AM parts was characterized by KEYENCE Digital MicroscopeVHX-7000 and Phenom XL Desktop SEM. The experimental results show that electroless nickel deposition produces uniform Ni coating on the additively manufactured components up to 20 µm per hour. Mechanical properties of as-built and Ni coated AM samples were analyzed by applying a standard 10 N scratch test. Nickel coated AM samples were up to two times scratch resistant compared to the as-built samples. This study suggests electroless nickel plating is a robust viable option for surface hardening and finishing AM components for various applications and operating conditions.</p>

Surface Finishing and Electroless Nickel Plating of Additively Manufactured (AM) Metal Components

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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