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Microstructural characterisation of Co-Cr-Mo casting dental alloys

Szala M., Beer-Lech K., Gancarczyk K., Kilic O., Pędrak P., Özer A., Skic A.

Advances in Science and Technology. Research Journal

2017

Vol. 11, no 4

76--82

The study compares the microstructure of three commercial dental cobalt matrix alloys with related chemical composition declared by the manufacturer. Casts were produced with lost wax method, then melted and casted with centrifugal induction casting machine. The Co-Cr-Mo alloys were casted according to the manufacturers procedure. The samples’ chemical composition and phase composition, respectively, using WDXRF (Wavelength Dispersive X-Ray Fluorescence) and XRD (X-ray Diffarction) methods were analysed. Casts microstructure by mean of LOM (Light Optical Microscopy), SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy) were investigated. Vickers hardness HV10 was measured. Quantitative microstructure evaluation was performed by means of computer image processing. The results of the chemical composition indicate the high stability of the chemical composition for alloy A. In case of alloys B and C, there was a significant difference in carbon content. Quantitative differences in image of microstructure between of castings A and B, C were noticed. The greater amount of precipitates was recorded for castings with higher carbon content. In all investigated castings, the presence of β matrix solution and M23C6 carbide precipitations was found.

Stress-strain curves under compression for CMSX4 nickel based superalloy

Nowotnik A., Pędrak P., Rokicki P., Mrówka-Nowotnik G., Sieniawski J.

Advances in Manufacturing Science and Technology

2014

Vol. 38, nr 3

65--77

Variations of a flow stress vs. true strain illustrate behavior of material during plastic deformation. Stress-strain relationship is generally evaluated by a torsion, compression and tensile tests. Results of these tests provide crucial information pertaining to the stress values which are necessary to run deformation process at specified deformation parameters. Uniaxial compression tests at the temperature through which precipitation hardening phases process occurred (900-1200°C), were conducted on superalloy - CMSX-4, to study the effect of temperature and strain rate (ε =10 to the -4 and 4x10 to the -4 s to the -1) on its flow stress. On the basis of received flow stress values activation energy of a high-temperature deformation process was estimated. Mathematical dependences (σpl - τ i σpl - ε) and compression data were used to determine material's constants. These constants allow to derive a formula that describes the relationship between strain rate (ε), deformation temperature (τ) and flow stress σpl - ε = A1σ to the n ∙ exp(-Q / RT).

Zachowanie się materiału podczas odkształcania plastycznego na gorąco charakteryzują krzywe zmiany naprężenia uplastyczniającego w funkcji odkształcenia. Do ich oceny stosowane są próby skręcania, ściskania lub rozciągania. Pozwalają określić dane niezbędne do prowadzenia procesu przeróbki plastycznej materiału z zastosowaniem odpowiednich parametrów odkształcania - temperatury i prędkości chłodzenia. W pracy przedstawiono analizę wyników badań wpływu temperatury i prędkości odkształcania (ε = 10 do - 4 i 4 x 10 do -4 s do -1) na wartość naprężenia uplastyczniającego nadstopu niklu - CMSX-4 w zakresie wartości temperatury wydzielania cząstek faz umacniających (900-1200°C) uzyskane w jednoosiowej próbie ściskania. Ustalone wartości naprężenia uplastyczniającego były podstawą do wyznaczenia energii aktywacji Q procesu odkształcania wysokotemperaturowego. Na podstawie uzyskanych danych oraz odpowiednich zależności (σpl - τ i σpl - ε) określono wartości stałych materiałowych oraz ustalono zależność prędkości (ε), temperatury odkształcenia (τ) i naprężeniem ustalonego płynięcia plastycznego σpl - ε = A1σ do n ∙ exp(-Q / RT).

Mechanical properties of hot deformed Inconel 718 and X750

Nowotnik A., Pędrak P., Sieniawski J., Góral M.

Journal of Achievements in Materials and Manufacturing Engineering

2012

Vol. 50, nr 2

74--80

Purpose: Variations of a flow stress vs. true strain illustrate behavior of material during plastic deformation. Stress-strain relationship is generally evaluated by a torsion, compression and tensile tests. Design/methodology/approach: Compression tests were carried out on precipitations hardenable nickel based superalloys of Inconel 718 and X750 at constant true strain rates of 10-4, 4x10-4, s-1, within temperature through which precipitation hardening phases process occurred (720-1150°C) using thermomechanical simulator Gleeble and dilatometer Baehr 850D/L equipped with compression unit. True stress-true strain curves analysis of hot deformed alloys were described. Findings: On the basis of received flow stress values activation energy of a high-temperature deformation process was estimated. Mathematical dependences (σpl -T i σpl - ε) and compression data were used to determine material’s constants. These constants allow to derive a formula that describes the relationship between strain rate (e), deformation temperature (T) and flow stress σpl. Research limitations/implications Study the flow stress will be continued on the samples after the aging process. Practical implications: The results of high-temperature deformation of the examined Inconel alloys may possibly find some practical use in the workshop practice to predict a flow stress values, but only within particular temperature and strain rate ranges. The results of the study can be used in the aerospace industry to produce blades for jet engines. Originality/value: The results of the study can be used in the aerospace industry to produce blades for jet engines.