English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

A number of small investment cast nickel-base bolts used for fastening metallic heat shields in combustion chambers of large industrial gas turbine engines were found fractured upon a regular hot gas path inspection in one particular engine. No similar findings were reported from any other engine in the field. The fracture of a single-digit number of these fasteners in an individual engine did not cause the liberation of the respective heat shields, hence no secondary damage occurred. The subject bolts were fractured in the head region that is also used to apply the fastening torque upon assembly of the heat shields. No evidence of fatigue, creep or hot corrosion damage was found. From the results of the metallurgical failure investigation described in this paper it was concluded that the subject bolts failed by torsional and/or tensional overload. Severe embrittlement by precipitation of secondary phases due to long-term high temperature service exposure contributed to the failure. The bolts ran hotter than intended by design. It is likely that cracks were induced in the bolt heads by over-torquing them upon assembly. Those cracks later grew in service.

Metallurgical Failure Investigation of Overheated and Fractured Investment Cast Nickel-base Bolts Made of Inconel 939