All-Russia Institute of Light Metals wins award for functionally graded Ni-based superalloy disks
November 18, 2014
The International HIP committee (IHC) presented its ‘HIP Parts of Excellence’ award winners at HIP’14, the 11th International Conference on Hot Isostatic Pressing, Stockholm, Sweden, June 9-13. As previously reported, the Grand Prize was presented to GE Oil & Gas, however the IHC also presented a number of other awards in the competition.
The All-Russia Institute of Light Metals (VILS) JSC, Moscow, Russia, received an award for its Ni-based superalloy disks with a dual structure and functionally gradient properties manufactured by direct HIP.
Differences in the local operating conditions within a gas-turbine engine dictate different property requirements for disk hub and rim regions. The operating temperature in the hub section of the disk does not exceed an average of 550°C thus, high ultimate strength properties and low-cycle fatigue resistance is desirable in the hub section.
In contrast, the disk rim material requires high creep resistance and should display low fatigue crack growth rates while operating at temperatures of 650-750°C.
To achieve these desirable properties in the specific regions of the disk, the VILS group developed a technique which uses two powders to produce nickel-based superalloy disks having a functionally graded, dual structure.
Two approaches were used to achieve this type of structure: production of a dual structure disk from alloy VV750P powder in which structural variation was achieved though the selection of alloy powders having different particle sizes, and the production of a bi-metallic disk having a rim of alloy VV750P and bore from VV752P alloy.
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Fig. 1 A near net shape HIP PM disk (left) was produced from nickel-based VV750P PREP powder such that the the hub and the rim of the disk possessed two distinctly different microstructures
A 179 kg disk having a diameter of 524 mm, made using two different alloy VV750P powders, one fine and one coarse, was submitted to the competition. Fig. 1 shows an image of the disk prior to heat treat and Fig. 2 shows the microstructure in the transitional region between fine and coarse grained material in the HIPed material.
Fig. 2 The micrograph shows the transitional region between the fine grained hub section and the coarse grained disk rim. Microstructural examination showed that mean grain sizes in the fine-grained and coarse-grained regions of the experimental disk material were 28 and 53 µm respectively. The width of the transition region from fine grained to coarse-grained material was approximately 800 µm
