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Tuesday, May 16, 2006 - 10:30 AM
HTM062.4

Improving C1023 Manufacturability by Two-Step Heat Treatments

I. Hernández, A. Subinas, I. Madariaga, K. Ostolaza, Industria de Turbopropulsores, ITP S.A., Zamudio, Spain

C1023 alloy (Ni – 15.5% Cr – 9.7% Co – 8.3 % Mo – 4.1 % Al) is widely used in the manufacture of equiaxed nozzle guide vanes and seal segment for aero gas turbines. However, in spite of its extensive applications in many different types of engines, C1023 is considered difficult to weld, repair or machine. The high strength of this alloy is mainly due to the presence of a fine distribution of gamma prime precipitates that are formed directly after casting. The quick formation of this precipitates does not allow to process C1023 components with a soft material condition that could be comparable to the solution state of other superalloys. However, it would be desirable to achieve some kind of temporary soft condition that could improve the manufacture of C1023 components.

For this reason, a detailed study on the response of C1023 material to different kind of heat treatments has been conducted. These heat treatments were focused in two opposite directions. First of all, it was necessary to achieve a heat treatment capable to soften the material in order to improve all the aspects related to its manufacturability. After this, it was necessary to develop a second heat treatment that would be introduced at the end of the manufacturing process and that could be able to restore the high resistance of C1023.

The results have shown that it is possible to achieve a significant reduction on the hardness of C1023 after 4 hours at 1200ºC followed by a controlled slow cooling. A starting microhardness of 375 HV can be reduced to 341 HV. The subsequent application of a 1190ºC heat treatment for 1 hour followed by a combination of furnace cool and gas fan quench is able to restore the original hardness of the as cast material.


Summary: Although C1023 alloy is extensively used in aeronautic applications, the manufacture of C1023 components is not free of difficulties. The high resistance of this alloy in the as cast condition gives rise to many problems of manufacturability (weldability, repairability, machinability). The aim of the work presented in this paper is to develop a two step heat treatment that could soften the material to improve its manufacturability after the first step and that could restore the original high resistance of this alloy after the second step.