SiC 세라믹스의 표면 거칠기에 따른 강도특성

Abstract

In this study, according to effect of surface roughness, change of strength was analyzed. Typically, when ceramic applies to its field, crack on surface adversely affects mechanical property because of crack. End of crack on surface is very pointed and stress concentration occurs at end of crack. So when ceramic is grinded, grinding must be conducted until polished plan is made. After hear treating each ceramic atoptimum healing temperature for crack healing, if we can get ceramic having higher or similar strength than smooth specimen without polishing by 6μm grinding plate, cost of machiningcan be reduced substantially. As stated earlier, non polished smooth specimen and other specimens of SAY which were grinded at each grinding plate, 125μm, 40μm, 6μm, were hear treated at optimum healing temperature 1373K during 1hour to 10hours. And then specimens heat treated during 1hour to 10hous were used for getting strength property. And specimens spread with SiO2 colloid on surface of specimen were also heat treated at optimum healing temperature 1373K during 1hour and those specimens were also used to study on strength property. In accordance with effect of surface roughness, strength property at room and high temperature were researched. When grinding surface of specimen, grinding time, pressure, and grinding plate were changed for getting effect of surface roughness on strength property. And then 3point bending test was conducted at room and high temperature. After heat treating specimens, strength and mechanical property of smooth specimens increased but defect such as crack on surface of specimen were not destroyed perfectly. And strength improved by heat treatment was also limited. Generally, surface roughness affects bending strength. Therefore, the smaller surface roughness is, the higher bending strength become. But bending strength of specimens that were grinded by 40μm grinding plate and heat treated during 1 hour is higher than bending strength of specimens that were grinded by 6μm grinding plate and heat treated during 1 hour. Based on earlier experiments, crack by machining can be improved by using crack healing process without polishing by 6μm grinding plate.