Here are some images of various failed tungsten filament lamps. For more details see the report linked at the bottom of the article, this includes captions and discussion.
These micrographs were given to me as part of a project which made up part of my undergraduate degree: Case Study on Tungsten Filament Lamps. In the report it discusses the manufacture of Tungsten filament lamps, some of the physics involved and discusses some alternative light sources that can be used.
The project was taught with great enthusiasm by Prof. G. W. Greenwood.