Production of, a Ni based superalloy by mechanial alloying and investigation of its microstructure, mechanical properties and oxidation behaviour

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Thesis Type: Doctorate

Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey

Approval Date: 2007

Thesis Language: Turkish

Student: Mehmet Erdem

Supervisor: MEHMET TÜRKER

Abstract:

In this study a nickel based superalloy powders (75Ni, 20Cr, 4Al 2O3, 0.6Ti, 0.4 Y2O3%) were mechanically alloyed (MA) in a Szegvari type attritor under inert gas atmosphere for various durations ( ½ to 24 h) in stainless steel and ceramic containers. The powder analysis has revealed that the optimum particle size and the microstructure were obtained after 8 h mechanical alloying. Thus, blocks were produced from those powders. Microstructure, mechanical properties and oxidation behavior of blocks after sintering, hot deformation and secondary recrystallization were investigated. Particle size analysis, micro hardness tests, light microscope and scanning electron microscopes (with EDAX) analysis and X-RD methods were conducted on both mechanically alloyed powders and the produced blocks. Experimental results showed that; structure and properties of the powders changed with MA durations, grains with the mean size of 100 ım were obtained after secondary recrystallization heat treatment, ductile fracture behavior was observed after mechanical tests and weight gain was seen with increasing the oxidation time.