基于预合金粉末原料的粉床型电子束增材制造W-Ni-Fe-Co合金研究

Research on W-Ni-Fe-Co alloys fabricated by Selective electron beam melting from pre-alloyed powder

摘要:

采用等离子旋转雾化方法制备了W-Ni-Fe-Co预合金粉末,并进行了粉床型电子束增材制造成形。结果表明：W-Ni-Fe-Co预合金粉末由两种形貌的颗粒组成,一是球形粉末颗粒,二是由许多小颗粒粘结而成的不规则粉末颗粒。预合金粉末内部显微组织为γ- (Ni-Fe)相内部镶嵌着规则的W颗粒,γ- (Ni-Fe)相内部含有过饱和的W元素。在粉床型电子束增材造成形过程中,W-Ni-Fe-Co合金的显微组织显示出一定的遗传性,但是由于成形过程中细小的熔池会同时受到反冲压力、热毛细管力及马兰戈尼对流的作用,熔池的瞬时流动剧烈,促进了钨颗粒的重排过程,显微组织更为均匀。成形致密化过程主要为W颗粒的重排,并没有显著的W的溶解-析出过程。粉床电子束增材造成形的W-Ni-Fe-Co合金室温抗拉强度可达1098MPa,但是合金塑性较差，断裂方式主要为钨的穿晶断裂和周围γ- (Ni-Fe)相的韧性撕裂

Abstract:

W-Ni-Fe-Co pre-alloyed powder was prepared by plasma rotating electrode process, and then fabricated by selective electron beam melting (SEBM). W-Ni-Fe-Co pre-alloy powder consists of spherical powders and irregular powders with the microstructure of tungsten particles coated by γ- (Ni-Fe) phase, which contains supersaturated tungsten. Microstructure of the W-Ni-Fe-Co alloy shows a certain heredity from powder to SEBMed sample. The molten pool will be subjected to recoil pressure, hot capillary force and Marangoni convection during SEBM, the instantaneous flow of the molten pool promoted the rearrangement of tungsten particles, leading a higher uniformity in the SEBM sample than the powder. Densification process during SEBM is mainly the rearrangement of W particles, and there is no significant dissolution-precipitation process of W. The tensile strength of SEBMed W-Ni-Fe-Co alloy was measured to be 1098MPa together with a poor ductility. Fracture mode is brittle transgranular fracture and ductile tearing of γ- (Ni-Fe) bonding phase.