Author : Manab Mallik, Saikat Pan and Himadri Roy

The fracture toughness of a hot pressed ZrB2-20 vol.% MoSi2 based ultra high temperature ceramic composite was measured by the Vickers indentation method and single edge notch bend test (SENB). The material was tested for indentation fracture toughness (IFT) at room temperature at four different loads between 49.03 and 196.3 N and four different indentation times between 15 and 30 s. Different formulae that exist to evaluate IFT were compared. The influences of the indentation load and the dwell time on IFT measurement were investigated. Results confirmed that the transformation occur from Palmqvist crack system to median crack system between low load to higher loads. The Palmqvist crack model yielded an IFT of ~3 MPa√m, whereas, the median crack model yielded an IFT of ~3–4 MPa√m. It is seen that the use of actual crack system at a particular test load gives almost similar fracture toughness values which are measured by the standard conventional method.

Keywords: Borides, Ceramic, Fracture toughness, Hardness.

Article published in International Journal of Current  Engineering  and Technology, Vol.3,No.5(Dec- 2013)