Impression creep technique—An overview

Impression creep technique is a modified indentation creep test wherein the conical or ball indenter is replaced by a cylindrical, flat bottomed punch. The usefulness of this technique, pioneered by Prof. Li, is illustrated by application to a variety of problems in this laboratory. High temperature creep behavior of a number of metals and alloys, particularly estimation of the thermal activation parameters aiding the identification of the rate controlling mechanisms of creep, has been investigated. The technique has also been exploited to assess the ‘single crystal’ creep behavior vis a vis that of a polycrystalline sample. Utilizing the impression creep test, the creep behavior of individual zones in steel weldments has been examined. The simplicity and the utility of the impression creep test have been further demonstrated by its application to the study of superplastic behavior in alloys. This paper presents a cross section of the results obtained in the above investigations. It is concluded that the impression creep test technique is capable of yielding much of the information that can be obtained from tensile creep testing. Furthermore, it can provide data which are either impossible or extremely difficult to obtain with conventional creep testing.