IADR Abstract Archives
A Comparative Evaluation of “House of Cards” and “Cabbage Head’’ Fluormica Glass-Cramics
Objectives: Fluormica glass-ceramics are well known for its excellent machinability, which is attributed to its unique ‘’House of Cards’’ microstructure. Another interesting microstructure ‘’Cabbage Head’’ has been developed claiming better mechanical and machinable properties. MACOR® (MAC) and VITRONIT®(VIT) are two commercially available examples of both microstructures.This work studies the effect of different microstructures on properties of fluormica glass-ceramics .
Methods: Both glass-ceramics were characterized using X-ray diffraction (XRD), Scanning electron microscope (SEM), 19F and 27Al MAS-NMR. MAC and VIT were then tested using Knoop hardness test (KH), Biaxial flexural strength test (BFS) and their machinability has been evaluated.
Results: XRD of both showed crystallisation of potassium fluorophlogopite with almost no difference in number or intensity of diffraction lines, SEM of MAC showed plate-like crystals forming ‘’ House of cards’’ microstructure while that of VIT showed curved crystals aggregates with amorphous centre forming ‘’Cabbage head’’ microstructure. Knoop hardness of VIT was significantly higher than that of MAC, same as forces needed to machine them. The BFs of MAC was significantly higher than that of VIT.
Conclusions: Commercial fluormica glass-ceramics with House of Cards microstructure has a better machinability and biaxial flexural strength than the with Cabbage head microstructure. However, the latter has higher hardness.
Methods: Both glass-ceramics were characterized using X-ray diffraction (XRD), Scanning electron microscope (SEM), 19F and 27Al MAS-NMR. MAC and VIT were then tested using Knoop hardness test (KH), Biaxial flexural strength test (BFS) and their machinability has been evaluated.
Results: XRD of both showed crystallisation of potassium fluorophlogopite with almost no difference in number or intensity of diffraction lines, SEM of MAC showed plate-like crystals forming ‘’ House of cards’’ microstructure while that of VIT showed curved crystals aggregates with amorphous centre forming ‘’Cabbage head’’ microstructure. Knoop hardness of VIT was significantly higher than that of MAC, same as forces needed to machine them. The BFs of MAC was significantly higher than that of VIT.
Conclusions: Commercial fluormica glass-ceramics with House of Cards microstructure has a better machinability and biaxial flexural strength than the with Cabbage head microstructure. However, the latter has higher hardness.