چكيده به لاتين
Abstract:
In general cermets and especially alumina base cermet due to their favorable mechanical properties has been widely used in different industries. In cermet by increasing the amount of mettallic phase increasing of toughness and decreasing of hardness happen simultaneously. Along with the reduction in hardness, uses of cement decreases.In this study, spinel synthesis of raw materials, sintering of metal-ceramic composites and metal solid solutions used to preventing of hardness decreasing.
First, the effect of glycine-sulfate and citrate-sulfate chelating agent in combustion synthesis and citrate sol-gel synthesis was studied. Results show that glycine-sulfate chelating agent could not be prepared an Appropriate complex for spinel synthesis while citrate-sulfate chelating agent was appropriate to making complex that could form spinel at 700 ◦C.
In the second step, the composites reduction was investigated in three approaches namely carbon bed, reaction reduction with aluminum and reaction reduction with aluminum while sintering. Results show that reaction reduction by aluminum during sintering be the best choice because thereby achieving better microstructure without any extra heat treatment before sintering.
Finally, alumina-nickel, alumina-cobalt, and alumina-(nickel, cobalt (SS)) were sintered by spark plasma sintering method at 1400 ◦C for ten minutes with 95.4%, 94.5%, and 98.6% theoretical density respectively. The best bending strength was for alumina-(nickel, cobalt (SS)) 380 MPa in comparison with alumina-nickel with 357 MPa and alumina-cobalt with 354 MPa bending strength. Fracture toughness of alumina-(nickel, cobalt (SS)) was calculated about 14.6 Mpa.m0.5 while and alumina-nickel and alumina-cobalt fracture toughness were calculated about 9.2 and 9.1 Mpa.m0.5 respectively. The hardness of this composite was reported 11.8, 11.4 and 14.6 GPa for alumina-nickel, alumina-cobalt, and alumina- (nickel, cobalt (SS)) respectively. The hardness of these composites in comparison with the hardness of alumina sintered at 1600 ◦C, in the same way, showed that while hardness of alumina-nickel and alumina-cobalt composites declined about 27% hardness of alumina-(nickel, cobalt (SS) ) has declined only 7% .
Keywords: Alumina, Solid solution, Alumina-(ni,Co) composite, reduction, spark plasma sintering
