چكيده به لاتين
Silicon nitride ceramics are gaining recognition in the market as triboelements such as ball bearing, seal and engine parts. Si3N4 materials have lower density and thermal expansion than metals, and their mechanical stability and corrosion resistance over a wide range of temperature are superior to those of several other high-strength ceramic materials. Dense Si3N4 based materials can be fabricated by the use of additives to provide a liquid phase which allows sintering. However, the liquid phase promotes the formation of intergranular phases, which influence the mechanical and physical properties, depending on their composition, amount and distribution.
In this research, Y2O3 and Al2O3 additives was selected as the more proper one. Yttria and Alumina additives had been added to Silicon Nitride powder with 1:1, 1:2, and 1:3 weight ratio and cumulative weight percent of 9 and 12, and After adequate mixing, hot pressed at 1730 ℃. The highest density was related to the sample SN6/6 which was equal to 97% of theoretical density. This sample, also, had the most hardness (17.5GPa) but the lowest toughness (5.6 MPa.m1/2) among all other samples. Phase analyses which was conducted with XRD analyze, showed that 97% of Silicon Nitride phase was in β form and the phase related to SiO2-Al2O3-Y2O3 system is almost crystalized. All samples weretested for wear resistance and the friction coefficient obtained for them was in 0.38_0.5 range which is appropriate for wear resistance applications.
Keywords:Silicon nitride, sintering additives, hot press.
