Failure analysis/investigations are carried out to determine the causes that have led to the failure of a part, equipment or structure/s.
Causes of failures include, but are not limited to, design flaws, material selection, raw material issues or misapplication of the component. Undertaking failure investigations can help prevent failure reoccurrences, improve product design and therefore reduce costs and expense.
To begin a failure investigation, information is gathered regarding the part’s history, material type, specifications, processing technique, service conditions, and events preceding the failure. On part/product receipt, relevant tests are undertaken.
Rotech received a fractured chain anchor which had failed in service from a large manufacturer of transport solutions for logistics and warehouses.
Upon preliminary visual examination the chain anchor appeared to have fractured into two parts, with the fracture being at the end of the threaded section.
Both fracture faces appeared to be dark in appearance. The thread was tarnished for approximately two-thirds of its length and appeared to have material deformation at the fracture face. The non-threaded part of the component exhibited linear surface damage.
After Vickers low-load hardness testing was carried out (BS EN ISO 6507-1) and Chemical analysis was performed by Leco and Induction Coupled Plasma (ICP), our team of Metallurgists using the Scanning Electron Microscopy (SEM) revealed the presence of ductile dimpled fracture characteristics on the fracture face with no evidence on internal material flaws.
Sections were taken through the component to incorporate the fracture face, were mounted and prepared by standard techniques to enable metallographic examination by optical microscopy.
Upon initial examination, it was revealed that the material had significant quantities of non-metallic inclusions. Subsequent etching revealed the matrix to be mainly ferrite with pearlite.
The results showed that fracture characteristics are indicative of failure by tensile overload in a ductile manner.
The material composition did not meet that of the designated standard, with the sulphur content being significantly high, typical of a free machining type steel that will have lower mechanical properties when compared to the designated standard material.