LATTICE CHANGES IN THE MARTENSITIC PHASE DUE TO AGING IN 18 WT-PERCENT NICKEL MARAGING-STEEL GRADE-350

Changes in the lattice parameter of martensite phase in a maraging ste el is measured as a function of ageing temperatures. A decrease in the lattice parameter is observed when aged between 400-650 degrees C whi ch is attributed to the depletion of alloying elements in the martensi te matrix as a consequence of precipitation and austenite formation. A n increase in the lattice from 650 to 710 degrees C was characteristic of enrichment of alloying elements in the martensite matrix due to di ssolution of austenite phase. A minimum value of the lattice parameter of martensite is observed at 650 degrees C which coincides with the m aximum vol % of retained austenite. Electrical resistivity, hardness m easurements, and in situ high temperature dilatometry was also carried out to delineate various precipitation reactions that occur in this s teel.