The Metallography of Inconel X750 alloy
Metallography Characteristic:
When alloy x750 is solution-treated at 2100℉，the number of dislocations and crystal defects are reduced, and γ and soluble carbides go into solution. For best results, the material should be in a fairly heavily worked condition prior to the treatment to ensure rapid and complete recrystallization. Once the material has been solution-treated, it should not be subjected to any cold work since it will generate new dislocations and thus impair rupture properties.
Creep resistance of alloy x750 stems from the uniform dispersion of intragranular γ; whereas rupture properties are more closely related to grain-boundary area microstructure. During the 1550℉/24 hr stabilization treatment of the triple heat treatment, fine γ appears in the grain interiors and M23C6 is precipitated in the grain boundary;adjacent to the grain boundary is a zone denuded of γ. On precipitation treating (1300℉/20 hr),γ has precipitated in this denuded zone. γ particles arrest the motion of moving dislocations, thereby increasing tensile and creep-rupture properties.
During M23C6 transformation at 1550℉, the carbon is essentially stabilized, without leaving chromium-depleted areas at the grain boundaries. This stabilization improves the resistance of nickel-chromium alloys to attack by certain corrosive media.
By Lowering the precipitation temperature from 1350℉ to 1150℉, as described for certain specific heat treatments, additional γ can be caused to nucleate in smaller particles, increasing the hardening effect and thereby improving tensile properties.
