Development of Ni-Cr-Al alloy with high corrosion resistance and high strength.

DSA760 our developed Ni-based alloy with composition of Ni-38Cr-3.8Al (mass%) has been applied on various applications, such as automotive parts, exhaust valve for marine engine, medical parts and a die for hot forging because it has high corrosion resistance and high strength.

The chemical composition of DSA760 is simple, but it has a complex microstructure which consists of the discontinuous or cellular precipitation of the Cr-rich solid-solution (α) phase with the body-centered cubic (bcc) structure combined with the continuous precipitation of the Ni₃Al (γ’) phase with the L1₂ from the Ni-rich solid-solution (γ) phase with the face-centered cubic (fcc) structure. Due to the cellular precipitation, the untransformed matrix of the γ phase is transformed into the cell consisting of the γ and α lamellar dispersed with fine γ’ particles.

It is known that Ni alloys congaing high Cr concentration exhibits excellent corrosion resistance so that Ni-Cr alloys have been used at severe hot corrosive components. DSA760 also has excellent corrosion resistance and the sulfidation corrosion resistance and vanadium attack resistance of DSA760 is superior to conventional Ni – based alloy, such as Alloy718, Alloy625, and Alloy80A. In addition to high corrosion resistance, it is reported that the strength of DSA760 is superior to that of conventional precipitation-strengthened Ni alloys. Actually, the strength of DSA760 reaches 2 GPa and 600HV after an appropriate heat treatment even though the hardness is lower in solution heat treatment.