Near-net Shape Processing of High Nb Containing TiAl Alloying Powder by Gelcasting

摘要

Gelcasting,a near-net-shape ceramic processing technology,is introduced here for Ti-Al components. Spherical Ti-45Al-8. 5Nb-(W,B, Y) alloying powders were prepared by argon plasma process,and then were near-net shaped by gelcasting. This study presents the gelcasting of Ti-Al-Nb alloying powders:Monomer in the non-aqueous system was methaerylate-2-hydroxy ethyl (HEMA) with toluene solvent. The initiator and catalyst were benzoyl peroxide (BPO) and N,Ndimethylaniline respectively. To improve sintering and forming behaviors,many additives are included in the suspension during gelcasting. Concentrated suspension where solid loading is up to 70 % was prepared during experiment. The influences of process parameters on apparent viscosity of the suspension were analyzed. The microstructure of the vacuum sintered high Nb containing TiAl was analyzed by using electronic microscopy (SEM) and X-ray diffraction (XRD). The ratio between the monomer (HEMA) and toluene solvent has great effect on the properties of solidified colloid and the more initiator and catalyst added the shorter the idle time is. The green bodies were polymerized through the monomer (HEMA) and had a smooth surface and homogeneous microstructure, with a bending strength as high as 60 MPa. It should be emphasized that the combination of plasma spheroidization and gelcasting is effective to obtain high-performance near-net shape products. After vacuum sintering at 1480°C for 2h,uniform complex-shaped high Nb containing TiAl parts were successfully obtained. The samples exhibited compressive at room temperature with compressive strength of 1715 MPa,compression ratio of 1. 85%.