Abstract
The addition of hard particles in a ductile alloy may lead to a substantial increase in its hardness and in the difficulty to machine it. The present work aims to specify the role of chromium carbides in the hardness of cast nickel alloys. A Ni–30 wt-%Cr alloy and six 0·2–2 wt-%C containing alloys based on the first one were elaborated by foundry. Their microstructures after aging at 1000, 1100 and 1200°C were described, and the room temperature, Vickers hardness of all the alloys for the three aging treatments were measured. Hardness increases with carbon content following a curve which is almost parabolic, while it increases more linearly versus the volume fraction of carbides. Hardness is generally lowered by choosing higher aging temperature. The evolution of hardness was compared with a law of mixture based on the hardness and the volume fractions of the matrix and of the carbides.
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