## 1 Introduction  
Net-shape parts of typically intricate and complex shapes obtained by powder metallurgy and additive manufacturing (AM) are employed in several key mass industry sectors, especially automotive, aerospace and medical. Their use is growing rapidly in preference to conventional casting because most PM processes produce parts in the desired precise final shape with little or no further machining requirement. Moreover the use of fine-grained (nano/micro scale), pre-alloyed homogeneous powders allows the manufacturing of parts with precisely set material properties and microstructures for increased strength. In conventional PM, powders are blended and compacted by cold pressing in a die and sintered in a furnace whereby the bonding between the particulates is further consolidated [1,2]. A significant drawback, however, is that following powder compaction, unwanted features like porosity (Figure 1) and cracks (Figure 2) in the microstructure, may remain [3,4] which can survive into the sintering phase, developing into critical flaws and defects. Similar defects can be observed in other additive manufacturing methods such as laser cladding and laser sintering, where the raw material is in the form of particulates, in addition to the ever present risk of delamination (Figure 3) that can occur between the added layers [5; 6; 7]. If undiscovered, these flaws may result in unwanted mechanical properties of parts that, can introduce a level of unreliability to the product. End-of-line inspection, not often performed, leads to the scrapping of 6-8% of components, yet fails to detect micro-sized defects, which can grow in service to produce major in-service failures and recalls. In terms of conventional press and sinter PM, the production can be improved significantly by introducing such an inspection system to the process. It is understood that the majority of defects originate in the pressing phase [4]. Optimisation of the pressing tool and the pressing process is, therefore, crucial for the final product quality. In most cases, the optimisation is based on a series of trials where the commonly used method to inspect the green parts is through destructive testing following sintering. These organisations use metallography as the main destructive testing method. As metallography, due to its nature, cannot provide accurate and reliable results in the full volume of the part [8], the tool optimisation requires numerous repetitions. The current tool and process optimisation, therefore, results in high tooling costs and lengthy setting up periods, limiting the growth of this manufacturing technique [9]. An Non-Destructive Testing prototype system has recently been developed which utilises the advantages of computed tomography to enable online (real time) quality assurance of powder metallurgy products [10; 11]. The system is capable of detecting bulk porosity, loss of material, delamination, and also captures microscopic cracks (surface breaking or volumetric) at any stage of the manufacturing process, therefore, potentially reducing production costs of material, energy, and time for the manufacturers by identifying faulty parts. The system uses Computed Tomography technique to capture the data from the parts' internal structure including any defect like features. From few hundred to couple of thousands of X-ray projection images are taken per part. These images are forwarded to a CT reconstruction tool that in our case uses the Filtered Back Projection technique and is developed by the Fraunhofer-Institut fur Integrierte Schaltungen. The 3D reconstructed image is than fed into the automated defect recognition module. As the final step in the process, the ADR system enhances the quality of the 3D CT image in order to highlight the areas of potential defects. Following image processing these highlighted areas are separated from the background and being classified in comparison with pre-set data from the image library.