Wear surface damage of a Stainless Steel EN 3358 aeronautical component subjected to sliding
The present paper describes the failure analysis of an aircraft component subjected to severalepisodes of in service failure, resulted in loss of the aircraft safety. Modern aircrafts are provided withmechanical systems which have the task to open not pressurized hatches during landing. The components ofsuch systems are subject to considerable mechanical stresses in harsh environment (presence of moisture andpollutants, significant and sudden temperature variations). The system is constituted by a sliding piston, arelated nipple and by a locking system consisting of 4 steel spheres which are forced into a countersinkmachined on the piston when the hatches is open. The whole system is activated by a preloaded spring. Themachined parts, nipple and piston, are made of EN3358 steel (X3CrNiMo13-8-2), a precipitation hardeningstainless steel with very low content of carbon often used in the aerospace. The samples provided by themanufacturer present different types of damage all referable to phenomena relative to the sliding of the pistoninside the nipple. The present paper describes the different damage observed and the microstructure of thematerial, then are reported the results obtained from the characterization of the material of the samples bymeans of optical and electronic microscopy, carried out to define the mechanisms involved in the systemseizure. In order to define the primary cause of failure and to propose solutions to be adopted, also analyzingthe criticality of using this PH stainless steel for this application, the results of different tests were comparedwith system design and working data.