Inconel 600 and 625 are both solid-solution strengthened nickel chromium alloys. They are used for their corrosion resistance more than their high temperature counterparts. They are commonly used in applications where corrosion and strength are of concern such as in the oil and gas industry.
Inconel 600 forms a stable nickel-chromium-iron solid solution with finely dispersed carbides. Likewise, Inconel 625 is a nickel-chromium-iron-molybdenum alloy that forms a solid solution with finely dispersed carbides. However, Inconel 625 has greater strength and slightly better corrosion resistance due to its greater amount of alloying and higher chromium content.
The below photomicrographs are of a sample of first Inconel 600 and second Inconel 625 at 500X magnification. The samples were taken from bar stock, hot mounted, ground, and polished to a sub-micron final polish. The samples were then etched using either Waterless Kalling’s or a mixture of Hydrochloric Acid and Hydrogen Peroxide. The microstructure of both samples consists of fine twin grains (solid solution matrix) with finely dispersed carbides.
Waterless Kalling’s:
12 grams Cupric Chloride, 20 mL Hydrochloric Acid, 225
mL Ethanol
Hydrochloric Acid/Hydrogen Peroxide:
6 mL Hydrochloric Acid to 4 drops Hydrogen Peroxide
(30% concentration)
(MUST BE USED QUICKLY ONCE MIXED)
