EBSD study of early fractured phenomena in a 350 grade Maraging steel elbows exposed to hydrofluoric acid

Abstract

The effect of grain orientations, boundary characteristics, and crystal effects on the crack formation of a 350 high strength Maraging steel elbows exposed to hydrofluoric acid was investigated in the present research. Tempered low tetragonal martensite and fresh martensite were characterized by scanning electron microcopy. Moreover, no segregation zone and precipitates were found near the crack path. Detail analyzing the spatial distribution of crystal orientations by electron backscattered diffraction technique revealed the development of two soft and hard grains. Soft grains oriented approximately along {110} planes provide adequate slip systems to promote dislocation mobility, indicating as low Taylor factor grains distributed well the strain gradient. However, hard grains associated with low compact {001} planes decrease dislocation mobility and increasing the strain accumulation. Micro-cracks initiation and propagation along these high internal energy grains are expected consequently.