Microstructure and Characteristics of High Nitrogen Austenitic Stainless Steel Component with High-strength and High-hardness Deposited by Double-wire and Plasma Arc Additive Manufacturing Process
TANG Ronghua1,2, FENG Yuehai1,2, LIU Siyu3, CHEN Qi1
1 School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China 2 MIIT Key Laboratory of Intelligent Controlled-arc Additive Manufacturing, Nanjing University of Science and Technology, Nanjing 210094, China 3 Shanghai Spaceflight Precision Machinery Institute,Shanghai 201600, China
Abstract: The low utilization rate of plasma arc and low deposition rate of single-wire and plasma arc additive manufacturing (SW-PAM), which is easy to cause overheating of the deposited layers. Therefore, the plasma arc additive manufacturing process with double wire melted into eutectic pool by single arc was used to manufacture the HNS thin wall samples, in which the high nitrogen austenitic stainless steel (HNS) wire was used as the filling wire. Then sizes of samples, deposition rate, microstructures, mechanical properties and fracture modes of HNS components with high-strength and high-hardness were tested and analyzed by vernier caliper, optical microscope, SEM and mechanical testing machine compared with the HNS thin wall samples fabricated by SW-PAM process. Moreover, the influence of the increase of volume of wire on the microstructures and mechanical properties was investigated in detail. Furthermore, the microstructure evolution and property change mechanism of HNS thin wall samples deposited by double-wire and plasma arc additive manufacturing (DW-PAM) were revealed. Experiment results show that the total wire feeding speed of DW-PAM process can be multiplied, and the stratification is clearer, besides, the average effective deposition rate is increased by 92% under the same deposited current in contrast to the SW-PAM deposited components. In addition, the microstructure of samples composed of a large quantity of austenite columnar dendrites with parallel additive direction, few d-ferrite and some dispersed nitrides, and the growth direction of few austenite grains is inconsistent can be observed in. Meanwhile, the ultimate tensile strength of HNS thin wall samples deposited by DW-PAM process is increased to a maximum of 44 MPa, and the elongation is also increase, with a maximum increase of 9.4%. The microhardness testing results expressed that the microhardness of samples fabricated by DW-PAM process is slightly higher than that of SW-PAM deposited components.
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2022, Vol. 36 
