This paper describes the development of new Si3N4 ceramics with both low friction coefficient and high strength, aiming at the reduction of friction force between cylinder liner and piston ring in low heat rejection engine.
Si3N4 ceramics has high Young's modulus, therefore it provides lower coefficient of friction than iron. We thought that if adsorption ability of Si3N4 to lubricant oil were improved, coefficient of friction got still lower. In order to achieve this Fe3O4, which has superior adsorption ability, were used as one of additives for Si3N4. The obtained new Si3N4 had obviously lower coefficient of friction than conventional Si3N4 and it's strength were almost same as conventional Si3N4. Moreover, cylinder liner and piston ring were fabricated from developed Si3N4. They were tested using engine and reduction of friction force was confirmed.