Differences in creep performance of a HIPed silicon nitride in ambient air and inert environments

High temperature tensile creep studies of a commercially available hot isostatically pressed (HIPed) silicon nitride were conducted in ambient air and argon environments. The creep performance of this HIPed silicon nitride was found to be different in these environments. The material crept faster (and had a consequential shorter lifetime) in argon than in ambient air at 1370°C at tensile stresses between 110- 140 MPa. The stress dependence of the minimum creep rate was found to be ≈ 6 in argon and ≈ 3.5 in air, while the minimum creep rates were almost an order of magnitude faster in argon than in air at equivalent tensile stresses. Differences in the creep performance are explained with reference to the presence or absence of oxygen in the two environments.