Effect of Heat Treatment on Strain Rate Sensitivity in Tensile Properties of 13Ni-15Co-10Mo-0.2Ti Maraging Steel

Abstract

Tensile properties and resistivity changes during isothermal aging have been investigated mainly on a 13Ni-15Co-10Mo-0.2Ti maraging steel aged in the range from 400° to 575°C. A crosshead speed has been varied from 1mm/min to 0.005mm/mim, in order to investigate the effect of strain rate on the tensile properties.
The embrittlement caused by the decrease in strain rate is found in the tensile properties of the maraging steel containing fine and coherent precipitates. The ductility of the overaged 13Ni-15Co-10Mo-0.2Ti maraging steel is also decreased at a lower strain rate. When this steel is averaged after cold rolling to 40%, the ductility parallel to the rolling direction is not decreased by the decrease in strain rate. Tensile properties insensitive to strain rate are obtainable after aging for about 10-100min in the range from 525° to 575°C.
Investigation carried out on 14Ni-10Co-10Mo and 14Ni-15Co-7Mo maraging steels is included in order to consider the effect of chemical composition on the strain rate sensitivity. The maraging steels containing fine and coherent precipitates are also embrittled by the decrease in strain rate. The 14Ni-15Co-7Mo maraging steel continues to precipitate coherent precipitates for longer times at a certain aging temperature than does the 14Ni-10Co-10Mo one.