Characteristics of negative creep and effect of boron on the creep properties of IN617 superalloy

Abstract

This study investigated the effect of the addition of boron on the creep properties and characteristics of the negative creep phenomenon at 1000 °C in applied stress of 18, 32, and 45 MPa. The results showed that boron addition led to a slightly longer creep life under the tested conditions, with the difference between boron-added and boron-free specimens becoming more noticeable at higher applied stresses. During prolonged creep operation under low applied stress (18 MPa), nitrogen diffused into the structure, leading to the formation of a hard and brittle AlN phase, which weakened long-term creep resistance. Also, the creep strain-time curves of both specimens revealed an unusual negative creep phenomenon. Localized chromium enrichment and the associated contraction of the lattice parameter due to short range ordering (SRO) formation was discussed to be the cause of negative creep.