双填丝等离子弧增材制造高强高硬高氮钢组织与特性研究

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

针对等离子单填丝增材制造电弧热量利用率低和熔丝效率低,容易造成增材金属过热的问题,以高氮钢丝材为熔化材料,采用单电弧双填丝共熔池的等离子弧增材制造工艺制备了高氮钢直壁体试样。采用游标卡尺、光学显微镜、扫描电镜和力学性能试验等手段,分别对单填丝和双填丝两种工艺增材直壁体的成型尺寸、熔敷效率、显微组织、力学性能和断裂形式进行了对比检测分析。然后详细考察了丝材熔敷量增加对试样组织和力学性能的影响,并分析双填丝等离子弧增材制造高强高硬高氮钢构件的组织变化规律和性能变化规律。结果表明,相对于单填丝增材工艺,在同样的增材电流下,双填丝增材工艺中总填丝速度可以成倍增加,分层更加清晰,平均有效熔敷效率提高92%。试样的显微组织大部分为平行增材方向奥氏体柱状树枝晶,存在少量的δ铁素体和弥散分布的氮化物,少量奥氏体树枝晶生长的方向出现不一致。在同样的电弧进行速度下,双填丝等离子弧增材制造的试样的抗拉强度均有明显提升,最大提升可达到44 MPa;断后伸长率均有增加,最高提升了9.4%。试样的显微硬度比单填丝增材试样的显微硬度略有提高。

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.