Inconel 718 Impact Strength
Inconel 718 Impact Strength
(OP)
We are experiencing occasional surface denting from rough handling impacts (at ambient temperature) on a thin wall pressure vessel made of Inconel 718. Mechanical properties at ambient temperature for this part have been spec’ed as follows. Test bars are prepared in the longitudinal direction to forging.
Yield = 165ksi, min (@ 0.2% offset)
El = 15%, min.
(Strain rate .005/minute.)
CVN Impact Strgth = 3 ft-lbs min
Dealing mainly in steel alloys, I was astounded at the low CVN specified for this material. Test bars are breaking at around 7 ft-lbs, so we don’t have a problem meeting the spec, however can anyone offer an academic explanation at the microstructural level as to why this alloy has such a low impact strength in view of the pretty decent El? Yes, strain rates are vastly different; maybe dislocations don’t ‘like’ moving quickly around the precips, etc. Could that be why? This may not solve our rough handling problem but I was just wondering about this apparent contraindication between CVN and El. (No, I’m not a student, wish I was still.) Thanks.
PS - There is no internal pressure at the time of denting.
Yield = 165ksi, min (@ 0.2% offset)
El = 15%, min.
(Strain rate .005/minute.)
CVN Impact Strgth = 3 ft-lbs min
Dealing mainly in steel alloys, I was astounded at the low CVN specified for this material. Test bars are breaking at around 7 ft-lbs, so we don’t have a problem meeting the spec, however can anyone offer an academic explanation at the microstructural level as to why this alloy has such a low impact strength in view of the pretty decent El? Yes, strain rates are vastly different; maybe dislocations don’t ‘like’ moving quickly around the precips, etc. Could that be why? This may not solve our rough handling problem but I was just wondering about this apparent contraindication between CVN and El. (No, I’m not a student, wish I was still.) Thanks.
PS - There is no internal pressure at the time of denting.





RE: Inconel 718 Impact Strength
Which heat treatment was used? This is very important since you can heat treat this alloy either to maximize strength or to maximize the stress-rupture.
Being an age hardened alloy the structure is loaded with very hard secondary phases. The alloys used to make turbine blades have the same issue.
Your values seem low, but I am not sure which condition we are talking about. I have seen them range from 20 lb-ft to 50 lb-ft.
http://www.specialmetals.com/assets/documents/allo...
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P.E. Metallurgy, Plymouth Tube
RE: Inconel 718 Impact Strength
RE: Inconel 718 Impact Strength
RE: Inconel 718 Impact Strength