Damping Capacity and Pitting Corrosion Resistance of Fe-Co-Cr Alloys

Abstract

The damping capacity, the magnetic property and the anodic polarization behavior were investigated on ternary Fe-Co-Cr alloys with Co less than 30% and Cr less than 40%. Measurements of the internal friction Q⁻¹, the coercive force H_c and the pitting potential E_p were carried out using an inverted torsion pendulum, an automatic recording fluxmeter and a potentiostat, respectively.
In the furnace-cooled state, a fairly high Q⁻¹ value was obtained in two composition ranges of Fe-3-5%Co-17-22%Cr and Fe-5-25%Co-0-5%Cr. Upon water-quenching, the Q⁻¹ value of alloys containing a large amount of Cr increased remarkably, but that of the alloys containing a small amount of Cr decreased considerably.
The Q⁻¹ of the alloys in the state of α solid solution was very high because of the small H_c. The alloys, in which the α-γ transformation strain remained and the σ, γ or ε phases precipitated in the α phase matrix, were lower in Q⁻¹ because of the large H_c.
In all cases the Fe-Cr binary alloys became higher in E_p with increasing Cr content, and the Co addition resulted in a further increase. The E_p of the water-quenched alloys was generally higher than that of the furnace-cooled alloys.