| Summary: | Metal parts formed by laser additive manufacturing methods usually have large surface roughness, which affects the corrosion resistance of the parts. This study reported the reason for and mechanism of the large surface roughness of 316L stainless steel samples manufactured by selective laser melting (SLM) at different build angles. Through the study, the reason for the large top surface roughness (average surface roughness is 15.3 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mrow><mi mathvariant="sans-serif">μ</mi><mi mathvariant="normal">m</mi></mrow></mrow></semantics></math></inline-formula>) is due to the molten channel structure formed on the surface. The large side surface roughness (average surface roughness is 19.1 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mrow><mi mathvariant="sans-serif">μ</mi><mi mathvariant="normal">m</mi></mrow></mrow></semantics></math></inline-formula>) is due to the incomplete fused particles adhering to the surface. Through electrochemical experiments, the influence of the build angle and polishing treatment on the corrosion resistance of the sample was studied. The different roughness of the top and side surfaces results in different corrosion resistances (the top surface pitting potential is 0.317 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>V</mi><mrow><mi>A</mi><mi>g</mi><mo>/</mo><mi>A</mi><mi>g</mi><mi>C</mi><mi>l</mi></mrow></msub></mrow></semantics></math></inline-formula> and the side surface pitting potential is 0.148 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>V</mi><mrow><mi>A</mi><mi>g</mi><mo>/</mo><mi>A</mi><mi>g</mi><mi>C</mi><mi>l</mi></mrow></msub></mrow></semantics></math></inline-formula>), and polishing can improve the surface corrosion resistance of specimens by reducing the surface roughness, especially for the side surface (from 0.148 to 0.351 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>V</mi><mrow><mi>A</mi><mi>g</mi><mo>/</mo><mi>A</mi><mi>g</mi><mi>C</mi><mi>l</mi></mrow></msub></mrow></semantics></math></inline-formula>). Therefore, parts manufactured by SLM can be post-treated to reduce roughness and improve surface corrosion resistance.
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