Gas atomisation has been shown to improve the properties of a Ni3AlCrZrB alloy. Both strength and creep resistance were found to exceed published data. This powder has been found to be suitable for compounding at high powder loads and to mould well. The debinding however must be performed slowly and the debound samples have low strength. The sintering behaviour is good with high densities being achieved through the application of liquid phase sintering. Coarser powder has also been moulded and sintered successfully, thus demonstrating the potential of liquid phase sintering to facilitate rapid densification of coarser powders. The sintering window is however rather narrow (15-20(C) and careful control of the process temperature must be maintained.
The alloy has been injection moulded to produce net shape tensile specimens and complex components for the endorsers. The properties of these moulded components approach those measured in the fully dense HIPed material and far exceeds published data for similar alloys produced by injection moulding.
The Ni3AlCrZrB alloy has been found to have enhanced oxidation and erosion and compares favourably to commercially available superalloys. However its high temperature wear resistance is limited and this restricts its application.
The addition of alumina fibres to the Ni3AlCrZrB alloy using the SCORIM process shows some potential but needs more development to improve the density of the final components. The alignment of the fibres within the intermetallic matrix has been demonstrated.
High pressure gas atomisation has been shown to be capable of producing large quantities of powder suitable for injection moulding and developments in the project have improved the efficiency, reliability and reproducibility of the process.
The proposed work endervours to establish the fundamental understanding required to develop a technology base for the exploitation of a range of intermetallic alloys.It addresses a number of problems hindering the wider application of these materials.Specifically it is aimed at improving the room temperature strength of nickel aluminides and setting upprocedures for the fabrication of near net shapes.
A number of novel processing techniques have been coupled with the recent knowledge of the physical metallurgy of these alloys to cover all aspects relating to the fabrication of net shape components in such compositions.
The following avenues will be explored:
a)Improvement of room temperature toughness.This will be tackled by alloying,by refining the microstructure through rapid solidification and by the controlled reinforcement with short,high melting point,ductile fibres.
b)Development of close coupled high energy gas atomisation to produce fine rapidly solidified powders and to control the particle size distribution.
c)Conventional and advanced MIM techniques will be employed to produce defect free mouldings from powder feedstock with and without fibre reinforcement.
d)Provision has been made to use the sinter/HIP process to fully densify compositions that are difficult to consolidate by pressureless sintering.
e)An extensive property assessment task has been included at the various stages of processing to correlate between processing conditions and microstructural development leading to final properties can be made.
Funding SchemeCSC - Cost-sharing contracts
UB8 3PH Uxbridge
2628 BL Delft