The role of oxidation damage in fatigue crack initiation of an advanced Ni-based superalloy

Abstract

Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Role of oxygen in enhanced fatigue cracking in a PM Ni-based superalloy: Stress assisted grain boundary oxidation or dynamic embrittlment?

“…In the fatigue crack initiation stage, it is believed that oxide cracking can result in crack initiation, which shortens the fatigue life. This is verified in a few studies which show much shorter fatigue life in preexposed disc alloys at elevated temperatures than for virgin/unexposed specimens [31][32][33]. In the crack propagation stage, enhanced intergranular crack propagation in the aggressive environment at elevated temperature is generally ascribed to the mechanism of stress assisted grain boundary oxidation (SAGBO) [6,7,16,20,25,[34][35][36][37][38] or dynamic embrittlement (DE) [18,19,39,40] at the crack tip.…”

Thermal Fatigue Characteristics of Type 309 Austenitic Stainless Steel for Automotive Manifolds

“…In addition, the role of environmental degradation is important in the thermal fatigue of a component. Oxide cracking can result in crack initiation and shortens the fatigue life of alloys at elevated temperatures [15]. There are two important mechanisms for the high-temperature oxidation to enhance the crack propagation, i.e., the stress assisted grain boundary oxidation [16] and the dynamic embrittlement [17].…”

The influence of stress on the oxidation of a Ni-based superalloy

“…As a result, internal oxidation of these elements can form and often does so as intergranular intrusions of silica in the stainless steels [24] or of alumina in the chromia-forming Ni-based superalloys [25][26][27]. This is a significant form of environmental degradation because fatigue cracks are known [28] to nucleate at alumina intrusions in the RR1000 superalloy used for aero-engine turbine discs. It is important to know whether the growth rate of such intrusions can be affected by imposed stress, i.e.…”