Hot Isostatic Pressing (HIP) has been used for many years to consolidate porosity in cast metal shapes to improve mechanical properties. When applied to fine metal powders, it is possible to produce Near Net Shape (NNS) items and more complex geometry components that are fully dense and offer an attractive set of properties at reduced cost. NNS items produced from HIPed powder deliver cost savings by reducing initial material usage and subsequent machining costs. Powder production and HIP processing are automated methods, which provide protection against forging route obsolescence. Setup costs are lower and batch sizes are smaller, which makes HIPping particularly well suited to small numbers of high integrity components. HIPed powder microstructures are isotropic and equiaxed, with uniformly fine grain sizes not normally achieved in heavy section components, which facilitates ultrasonic NDE examination. Improved features to facilitate NDE are readily incorporated into the HIP assembly. Inclusion contents are lower and of more benign geometry, easing fracture assessment. In a broad program of testing, Rolls-Royce has established (1) that HIPed powder 316L/304L components, in items up to several tons in weight, have equivalent or slightly better strength, toughness and corrosion resistance than the wrought equivalents. Rolls-Royce are extending their activities to HIPing of Inconel alloys. The first phase has been to HIP test samples of Inconel 600 and Inconel 690 alloys. Initial testing has produced promising results in line with expectations of wrought material. There has also been the opportunity to vary the HIPing cycle to assess the effect of processing parameters on the final product. An ability to HIP Inconel components is thought to be of benefit in new plant construction, where material is often not readily available in required thick section. The adaptability and good control of the HIP technique also shows promise as a manufacturing route for future high temperature materials which will be required in Generation 4 civil builds.
Study of Microstructure Features and Properties of Metals Obtained by Hot Isostatic Pressing
