Sheet lamination additive manufacturing of 316L/AISI 4140 parts using friction stir method

Abstract

Abstract The sheet lamination additive manufacturing was applied to fabricate 316L stainless steel/AISI 4140 alloy steel composite parts. The friction stir welding was used instead of ultrasonic to heat sheets. Different specimens with 2, 3 and 4 layers were fabricated. The insufficient heat input and the abnormal stirring induced two kinds of defects in specimens. The severe stirring and mixing of the low alloy steel and the stainless steel produced high hardness regions in the first layer of specimens as well as in the last one. The surficial hardness of about 600 HV was obtained for a 4th -layered specimen. The results showed that the conventional laminate composite formulas could not accurately predict the strength of fabricated parts due to the phase transformation and microstructural changes. The specimens showed superior ultimate strength values compared to the ultimate strength of both base metals and the maximum strength was about 1331 MPa. The fracture mode was a combination of ductile and quasi-cleavage fracture.