Microstructure, Thermo-Physical, Mechanical and Wear Properties of in-Situ Formed Boron Carbide - Zirconium Diboride Composite

Microstructure, thermos-physical, mechanical and wear properties of in-situ formed B 4 C-ZrB 2 composite were investigated.Coefficient of thermal expansion, thermal diffusivity and electrical resistivity of the composite were measured at different temperatures up to 1000°C in inert atmosphere.Flexural strength was measured up to 900°C in air.Friction and wear properties have been studied at different loads under reciprocative sliding, using a counter body (ball) of cemented tungsten carbide (WC-Co) at ambient conditions.X-ray diffraction (XRD) and electron probe microanalysis (EPMA) confirmed the formation of ZrB 2 as the reaction product in the composite.Electrical resistivity was measured as 3.02 × 10 -4 Ω•m at 1000°C.Thermal conductivity measured at temperatures between 25°C and 1000°C was in the range of 8 to 10 W•(m-K) -1 .Flexural strength of the composite decreased with increase in temperature and reached a value of 92 MPa at 900°C.The average value of coefficient of friction (COF) was measured as 0.15 at 20 N load and 10 Hz frequency.Increase of load from 5 N to 20 N resulted in decrease in COF from 0.24 to 0.15 at 10 Hz frequency.Specific wear rate data observed was of the order of 10 -5 mm 3 •(N-m) -1 .Both abrasive and tribo-chemical reaction wear mechanisms were observed on the worn surface of flat and counter body materials.At higher loads (≥ 10 N) a tribo-chemical reaction wear mechanism was dominant.