Tensile creep behavior of a gas-pressure-sintered silicon nitride containing silicon carbide

The tensile creep behavior of a gas-pressure-sintered silicon nitride conta ining silicon carbide was characterized at temperatures between 1375 degree s and 1450 degreesC with applied stresses between 50 and 250 MPa. Individua l specimens were tested at fixed temperatures and applied loads. Each speci men was pin-loaded within the hot zone of a split-tube furnace through sili con carbide rods connected outside the furnace to a pneumatic cylinder. The gauge length was measured by laser extensometry, using gauge markers attac hed to the specimen. Secondary creep rates ranged from 0.54 to 270 Gs(-1), and the creep tests lasted from 6.7 to 1005 h. Exponential functions of str ess and temperature were fitted to represent the secondary creep rate and t he creep lifetime. This material was found to be more creep resistant than two other silicon nitride ceramics that had been characterized earlier by t he same method of measurement as viable candidates for high-temperature ser vice.