17-7 RH950 Treatment on 17-4 PH

[mighoser]

Ok, I've got inseperable assembly made from both 17-7 & 17-4. The 17-7 is in the TH1050 condition and the 17-4 is in the H1075 condition. I'm interested in what a solution anneal(1950F)+austenite condition(1750F-> -100F)+age(950F)will do to the properties of the 17-4? I know the double aging process for 17-4 H1150M requires a two hour 1300-1500F treatment before final aging. I was thinking I could reduce the austenite conditioning step for RH950 from 1750 to 1500 since I have data on what this does to the RH heat treatment. In the end, I'll need to verify properties but I was wondering if anyone would know the effect. I'm sure someone has accidentally heat treated one of these two metal's to the other's heat treatment cycle.

Thank you

 

[NickE]

IMHO - You arn't going to get anything worth anything from 17-7 if you austenite condition at 1500, 17-7 is a pain cause seemingly minor changes in chemistry can cause significant changes in heat treat response.

 

[mighoser]

Data from:Armco 17-7PH and PH 15-7Mo Stainless Steel and Strip, Armco Steel Corporation, Middletown, Ohio, 119 pages (May, 1966)(RSIC 1931), details the effect of variation of austenite-conditioning temperature on the mechanical properties of the RH950 Condition. From this, variation of austenite condition temp between 1300-1750F has little effect. It apprears the frigeration cycle temp. is more crititcal in determining final properties. I know the TH heat treat is more sensitive to variation in austenite conditioning temp. Any idea what the 17-4 properties would be?