Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2014
Thesis Language: Turkish
Student: Uğur Gökmen
Supervisor: MEHMET TÜRKER
Abstract:In the study, the suitable rheological properties for powder injection molding process of feedstocks which have been prepared by using nickel based superalloy INCONEL 625 and different binder systems have been identified and also, the moldability of INCONEL 625 powder has been examined by using a unique binder in addition to two different classical binders. In the first stage, the rheological properties have been determined by preparing two different binders system (Polyethylene glycol / polypropylene/ stearic acid and paraffin wax/ carnauba wax/ polypropylene/ stearic acid) and feedstocks containing different proportions (59 to 71% by volume) of powder. A unique binder system (Polyethylene glycol / paraffin wax/ carnauba wax/ polypropylene/ stearic acid) has been developed in parallel to the results of rheology. In the second step, the feedstocks in different proportions have been prepared by mixing INCONEL 625 powder with the developed binder system and shear rate, viscosity, flow behavior index and the flow activation energy have been determined. For all rheology studies, the capillary rheometer temperatures have been changed between 110-200oC, while the pressure values have been changed from 0.165 to 2.069 MPa. It has been determined that the ideal powder loading ratio for the feedstocks prepared by the developed binder system and INCONEL 625 powder is %65 and the optimal flow behaviors in the powder loading ratio is in the range of 160-180oC. The feedstocks prepared by mixing INCONEL 625 (65%) and recently developed system binder (35%), have been molded as tensile samples. After the molding process the samples were subjected to thermal debinding, in solvent (heptane). Debinded samples have been sintered under an argon atmosphere with high purity at 1250, 1270, 1290, 1300 and 1310oC temperatures for 1h. The maximum theoretical density (98%) has been reached at the operations conducted at 1290 and 1300oC temperatures. Tensile tests have been performed after the sintering process, tensile strength and elongation % values have been determined. XRD analyses have been carried out to determine to lattice parameters and phases that may occur in the samples which were sintered at different temperatures. Microstructural changes of sintered samples have been examined by using SEM and optical microscopy. Elemental analyses have been performed by means of EDS and structural differences were examined.