Impression creep behavior of SiC particle-MoSi₂ composites

Using a cylindrical indenter (or punch), the impression creep behavior of MoSi₂-SiC composites containing 0–40% SiC by volume, was characterized at 1000–1200 °C, 258–362 MPa punch pressure. Through finite element modeling, an equation that depends on the material stress exponent was derived that converts the stress distribution beneath the punch to an effective compressive stress. Using this relationship, direct comparisons were made between impression and compressive creep studies. Under certain conditions, compressive creep and impression creep measurements yield comparable results after correcting for effective stresses and strain rates beneath the punch. However, rate-controlling mechanisms may be quite different under the two stressing conditions, in which case impression creep data should not be used to predict compressive creep behavior. The addition of SiC affects the impression creep behavior of MoSi₂ in a complex manner by pinning grain boundaries during pressing, thus leading to smaller MoSi₂ grains and by obstructing or altering both dislocation motion and grain boundary sliding.