CAVITATION EROSION RESISTANCE OF ACTIVE SCREEN-LOW TEMPERATURE PLASMA NITRIDED AISI410 MARTENSITIC STAINLESS STEEL

摘要

AISI 410 martensitic stainless steel specimens were low temperature plasma nitrided at 400°C in a mixture of 75%N2:25%H2, during 20 h. Active screen technic was used to avoid any edge effect. The nitrided case is composed of expanded martensite (a'n) and ε-Fe3N iron nitride, whilst chromium nitride precipitation was avoided. Surface hardness reached 1275 HV0.01. The transverse microhardness profile shows a gentle hardness gradient with a NHT nitrided case depth of 28 μm. The cavitation erosion mass losses were measured as a function of exposure time. The results showed a decrease of 27 times of the mass loss compared to the non-nitride specimens. Wear rate decreased from 2.56 mg/h for the non-nitrided condition to 0.085 mg/h after nitriding. Such results showed that low temperature plasma nitriding and the formation of expanded martensite are effective to increase cavitation erosion resistance of AISI 410 stainless steel.