Paper Title
FAILURE ANALYSIS AND MICROSTRUCTURE MODIFICATION OF CASTED MILL CRASHER DIAPHRAGM

Abstract
Abstract - This study investigates the failure roots and microstructure modification criteria of mill crasher diaphragm. Microstructure observation, chemical composition and hardness of samples were evaluated by optical and electronic microscope, spectral and x-ray map analysis and Vickers hardness test, respectively. The optical microscope analysis results of failed mill diaphragm showed the accumulation and propagation of heterogeneous cracks near the fracture surface. Presence of surface defects, propagation and branching of cracks on grain boundaries have been observed by SEM. In the examined areas the formation of manganese sulfide impurities detected by x-ray map analysis. EDS line scan analysis results showed that superficial chrome which led to intensified chromium oxide nucleation and growth, concurrently, chrome lack, observed in the under region, could be resulted in the cracks initiation and corrosion accelerating. On the other hand, In the modified diaphragm sample with the highest resistance to fracture, a homogeneous structure (without any localized or lacked chromium) and free from any surface defects and oxide layers was observed. In the addition, a decrease in the amount and number of inclusions (with a smaller average grain size) in modified sample microstructure was reported; this behavior was the good reason for better microstructural functionality at high erosion situation of casted mill crusher diaphragms. Keywords - Mill Crasher Diaphragm, Failure Analysis, Chrome Accumulation, Manganese Sulfide.