Crack Failure Analysis of 7Cr17MoV Steel Kitchen knife

A cracked 7Cr17MoV steel kitchen knife was analyzed by macroscopic inspection, hardness testing, chemical constituent test, metallographic inspection, scanning electron microscopy and energy spectrum analysis. The results showed that the cracking mode of the kitchen knives were stress corrosion; there were more large angular block carbides and uneven distribution of carbides in the kitchen knife material, causing stress concentration and initiation of microcracks, resulting in instability of the passivation film on the stainless steel surface. When the kitchen knives produced and processed in a chlorine-rich environment, chloride irons were preferentially corroded at the weakened passivation film to form corrosion pits. The bottom of the corrosion pit was microcracked due to stress concentration, and the chloride irons continued to corrode along the channels formed by the micro-cracks, which further expanded the microcracks. During the grinding process, the micro-cracks expanded outward under the action of external forces, resulting in cracking. (paper)