Development of hot isostatically pressed nickel based alloys for nuclear applications

Rolls-Royce has successfully established a capability for the hot isostatic pressing (HIP) of austenitic stainless steels in nuclear plant. The focus has now been extended to HIP of nickel based alloys, whose good material properties make their use in plant increasingly attractive. A development programme has been undertaken, comparing the mechanical property behaviour of HIP Alloy 600, 690 and 625 with their wrought counterparts. The results are promising, showing acceptable tensile properties and Charpy impact results for the HIP test pieces that are comparable to, or better than, the wrought data. It is concluded that HIP offers an attractive alternative manufacturing route that is ideal for the production of a small number of high integrity components. Hot isostatic pressing microstructures have the advantage of being isotropic and equiaxed, with uniformly fine grain sizes; properties not normally found in thick-section forgings.