Examination of metallurgical defects
Techniques: SE/BEI imaging, EDX spectroscopy, metallographic grinding/polishing
Summary: Castings, powder metallurgy products and weldments may contain various types of metallurgical defects, such as shrinkage pores, inclusions, gaseous pores, etc. Analytical SEM helps to examine the morphology, structure and chemistry of these defects and thereafter to identify the possible causes.
It regularly happens that internal cracks were found in cemented carbide parts where the cause(s) was not clear. The upper figure shows a round-shape particle on a fractured surface. Its chemical composition was determined by EDX spectroscopy to be Al-Si oxide.
The lower figure shows SEM-EDX examination of the poor surface quality of a Ni-B alloy laser weldment due to splash defect. Si-O inclusions were found in the polished section of the weldment as well as on the surface. The chemical composition of the inclusion was determined by quantitative EDX analysis.
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