Characterization and comparison of weaving printing patterns in wire arc additive manufacturing of austenitic stainless steel 316

Abstract

Printing patterns in additive manufacturing have been extensively studied regarding their effects on the microstructure and mechanical properties of the materials. However, weaving, a welding technique that produces good quality welds in large areas and ensures good weld penetration has not been applied in additive manufacturing. This study focuses on comparing four weaving patterns to two traditional line printing patterns in Wire arc additive manufacturing of austenitic stainless steel 316L. This thesis covers the groundwork of weaving pattern characterization, starting from optimization of printing parameters and printing path, followed by pattern characterization through measurements of voltage, current, thermal history, and thermal profile, and investigation of surface quality of the samples. Microstructure characterization was then conducted by optical microscopy, electron backscatter diffraction, and X-ray diffraction; and mechanical properties were obtained through microhardness and tensile testing. The weaving patterns showed an improved deposition rate and avoided lack-of-fusion defects compared to the line printing patterns. Two out of four weaving patterns achieved superior surface quality over the line printing patterns and are free of macro-defects such as side wall collapse and spattering. The weaving patterns have excessive heat accumulation and lower cooling rates compared to line printing patterns, which led to coarser microstructures and inferior microhardness and tensile properties. The thermal gradient is also more uniformed and aligned to the build direction, increasing the degree of grain alignment and texture of the weaving patterns across the samples.