| dc.description.abstract | A nickel-base superalloy for FCC power recovery turbine rotors
was developed, which shows excellent sulfidation-corrosion
resistance, high temperature strengths, and hot workability.
To investigate the influences of the alloying elements of
AISI685 on the sulfidation behavior, nickel-base alloys containing
each of chromium, cobalt, molybdenum, titanium, and aluminum
(the major components of AISI685), and alloys containing multiple
such elements were produced and corroded in sulfidizing gas
atmospheres at 600°C. It was found that the sulfidation behavior,
especially the penetrating behavior into the alloys, was greatly
influenced by aluminum, and that the resistance could be improved
by increasing the aluminum content in the alloys.
Six types of alloys, in which aluminum had been increased to
improve the sulfidation resistance of AISI685 and titanium
decreased by the same proportion to maintain the high temperature
strengths of AlSI685, were forged to test their sulfidation behavior
and high temperature strengths. As a result, the alloy with 1.5
percent titanium and 3.0 percent aluminum showed only half the
sulfidation depth of AISI685, for the tensile characteristics at
538°C, and at 850°C through 1100°C, equivalent or better than
those of AISI685. This means that the alloy with 1.5 percent
titanium and 3.0 percent aluminum has twice more sulfidationcorrosion
resistance than AISI685, in addition to equal or higher
high temperature strengths and hot workability.
A simulation expander rotor disk of 500 mm in diameter was
manufactured with the newly developed alloy. The disk was
successfully produced without shear cracking or buckling
problems. Furthermore, test specimens cut from the disk showed a
rupture strength equal to that of AISI685 at 650°C to 750°C. | en |
