Prakt. Met. Sonderband 52 (2018) 15 
The Failure Analysts’ Mightiest Tool - Thrilling Fractography of 
Metallic Components 
A. Neidel, E. Cagliyan, B. Fischer, T. Gädicke, M. Giller, S. Riesenbeck, T. Ullrich, 
S. Wallich* 
* Siemens AG, Power and Gas Division, Gasturbinenwerk Berlin, R&D Testing 
ABSTRACT 
In this contribution, some aspects of fractography are discussed, arguably the failure 
analysts' most potent analytical tool in metallurgical failure analyses. The characterisation 
of fracture surfaces is indispensable when it comes to getting to the bottom of things in 
regards to component failures. When machine parts or entire assemblies fail by fracture of 
individual members, the fracture surface contains the data that tells the failure analyst 
about the history of the failed component, and hopefully will also shed some light on the 
exact failure mode that eventually lead to fracture. That makes fractography, the art of 
reading fracture surfaces, so valuable. This applies to all material classes, i.e. metals, 
ceramics, and plastics alike. This paper, however, focuses on failures of metallic 
components only. When there is no fracture surface in a failed part, one is produced by 
forcing open cracks or other imperfections that might be suitable for this purpose. Once 
this is achieved, the failure analyst will open his or her toolset of macro- and 
microfractographic analysis equipment. It is not exaggerated to say that the scanning 
electron microscope (SEM) revolutionised the art of microfractography from the early 
1960s on. In this paper, a number of examples for this are given. 
1. Fatigue Fractures, The Failure Analysts’ Darling 
Every experienced failure analyst will agree with the statement that fractography is his or 
her mightiest tool when the task at hand is to tackle a failure case of a fractured metallic 
component. This is because the fracture surface is data storage for everything that 
happened to the component prior to and during the failure event [1] - [8]. When it comes to 
fractography, which is the art (it is certainly not a science) of reading fracture surfaces, 
fatigue fractures are the most liked in the failure analysis community of metallic parts. Why 
is that? It is because fatigue failures, under the right circumstances, can produce richly 
faceted fracture surfaces, containing a wealth of fracture features to be studied. On one 
end of the spectrum (the most difficult one), there are overload fractures of tool steels, 
which sometimes can be completely featureless. On the other end there are the fatigue 
fractures of ductile materials, such as aluminium and its alloys, titanium and its alloys, 
nickel and its alloys. and stainless steels. 
There are macrofractographic fracture features which are usually studied and 
photographed using low-powered light optical microscopes (LOM), often binoculars (stereo 
microscopes). More recently, virtual 3d microscopes were introduced in the laboratories. 
These devices can calculate images from non-polished, irregular, uneven surfaces like 
fractures by using only the in-focus areas from a multitude of images in a so-called image