THE EFFECT OF HEAT TREATMENT TEMPERATURES (ANNEALING, AGING AND DOUBLE AGING) ON HARDNESS OF 16%NI CAST MARAGING STEELS

Abstract

AbstractThe primary purpose of the present work was to study the effect of different annealing and aging temperature on the mechanical properties of 16%Ni cast Maraging steels. In addition subsidiary studies were made of the hardening mechanism responsible for high strength. It was found the annealing temperature must be done above approximate 750C◦ but not exceed 1250C◦ to give the good hardness during aging.. Marked hardening occurred within several minutes during from 485oC to545 oC but only after several hours in the range between 325 to 375 oC Heat treatment of 3 hour at 485 oC of cast alloys was most satisfactory. While the aging at 485 oC for long time decrease this hardening caused softening due to the reversion of the body centered cubic matrix to austenite. The aging kinetics mechanism refer to that lattice defect were influencing the reaction rate. X-ray diffraction evident indicated the formation of any bcc structure of matrix as martensite and the appeared that hardness was due to coherent precipitate having concentration in matrix that formed as Fe2CoNi,Ni3Ti and Ni3Mo phases. The double aging of cast alloys in different temperature given normal hardening result.