النتردة كأسلوب لإطالة عمر الأجزاء المعرضة لتحميل كلال متغير

Abstract EN

This study has aimed to illustrate the effect of one surface hardening method( Nitriding) upon fatigue life time of medium carbon steel alloys .

Therefore all tests.

concerning round bending of fatigue ,have been conducted at ordinary laboratory circumstances , within amean stress , [ value = 0&stress ratio ,R = -1], as stable and changing stress capacities , were forced in order to know the metal resistance to these stresses under the different dynamic loading .There by to give the safety life time of this metal , nitriding process (liquid & Gas ) was carried out to the metal ,which contributed in improving the fatigue resistance , as the improvement amount was based on the hardened depth , and the fatigue boundary , increases with nitriding layer depth .

strength tests, micro and hardening were carried out for the applied heat treatment circumstances ,because these tests are considered to be as criteria and connected with revelant correlation , concerning fatigue tests results .

Actually , micro structure examination has carried often before treatment , where as the micro structure was found before treatment [ ferrit & perlite ] while nitrogen phases were observed to be high with a layer of crome iron nitrides on the treated service with nitriding , that confirm the nitriding role in structural barriers formation on the service , that acts on stopping towards the crack..

Consequently, the images of (SEM) , regarding the fracture service , have declared a follow up images towards fatigue cracks .

This crack is originated under the thick hardened serface.Layer and developes , is a lease plastic region , as it was detected that fatigue life time , increases when loading from (high – low ) at the changing capacity of fatigue tests rather than( Low- High).