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

Abstract

The damping capacity, magnetic properties, anodic polarization behavior and mechanical properties have been investigated for ternary Fe–Co–Cr alloys with Co less than 30% and Cr less than 40%. Measurements of the internal friction Q⁻¹, the coercive forc H_c, the pitting potential E_P and the tensile strength σ_t were carried out using an inverted torsion pendulum, an automatic recording fluxmeter, a potentiostat and an Instron-type machine, respectively.
Upon furnace cooling, the alloys have fairly high Q⁻¹ over 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 of the alloys with higher Cr concentration shows a fairly high value.
The alloys in the state of α solid solution have very high Q⁻¹ because of the low H_c. The alloys, in which the γ→α transformation strain partially remains and the σ, γ or ε phase is precipitated in the α phase matrix have lower Q⁻¹ because of the high H_c.
In all cases the Fe–Cr binary alloys become higher in E_P with increasing Cr concentration, and the addition of Co results in an increase of E_P. The E_P of the water-quenched alloys is generally higher than that of the furnace-cooled alloys.