Resolution treatment of Maraging Steel 350

[will123]

Has anyone had experience of re-solution treating Maraging steel 300 or 350? It is supplied normally supply in this condition, however during machining of some parts I found a batch of this material begin distorting due to residual stress. I treated it for 1hour at 816C (the same as the initial treatment) however after finishing the part and aging it was discovered that full austenitising had not been achieved during the solution treatment and the material very soft and weak. I tried a few ideas to solve the problem and finally settled upon the method:-
3 thermal cycles between room temperature and 950C (with 1 hour dwell) to refine the grain structure
Then solution treat at 825C for 1 hour.
This worked reasonably well apart from a relativity high percentage of retained austenite.
My question is how can I reduced the amount of retained austenite? Will reducing the temperature t0 816C help.

 

[CoryPad]

I recommend you get two journal articles:

C. Hays and R.P. Stemmler, "AR-Aging as a New Approach for Enhanced Results", Journal of Materials Engineering and Performance (1998) v.7, pp. 733-738

C. Hays and R.P. Stemmler, "Banding of MAR-Aging Steel", Journal of Materials Engineering and Performance (2000) v.9, pp. 147-152

These detail heat treating of MAR-aging steels and how to reduce retained phases. Their recommended cycle is:

Anneal at 1057 deg C for 1 hour
Air cool to ambient temperature
Recrystallize at 789 deg C for 1 hour
Water quench to ambient temperature
Age at 517 deg C for 1 hour
Air cool to ambient temperature

Regards,

Cory

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