Failure Analysis on the Microstructure of Cr27Ni7 Chain Link Steel
The fracture failure on the microstructure of chain links with different term service has been analyzed by means of optical microscopy, scanning electron microscopy, microhardness tester, and X-ray diffractometer. The results show that the changes of carbides in the microstructure and grain- boundary weakness decrease tensile strength and impact toughness obviously, even though, without metallurgical defects (shrinkage porosity, inclusions), under long-term service of 900 ℃ thermal cycling conditions, which cause Cr27Ni7 chain link steel to approach or reach its lifespan. In order to prolong the service life of Cr27Ni7 chain links, trace elements instead of chromium should be added to strengthen grain boundary and form more stable carbides.