Non-destructive inspection of compacted parts
PM is the manufacturing route preferred in many industrial sectors because it does not require extreme conditions. A broad range of parts – such as transmission and gearbox steel parts for the automotive industry, cemented carbides for metal, wood and stone-working – are produced by cold compaction of metal powders in a die. This is followed by sintering the resulting green part at low temperatures. A major concern in PM is centred on the unpredictable formation of defects in parts. While surface cracks are detectable by inspection, internal defects are hard to detect. EU-funded scientists initiated the project DIRA-GREEN (Enable the powder metallurgy process to expand to new markets with more reliable parts and lower manufacturing costs through the inspection of green parts) to develop the much-needed non-destructive testing (NDT) equipment. The researchers focused on developing an inspection tool for improved assessment of green parts that is affordable for small and medium-sized enterprises (SMEs). This new tool uses DR to generate a density map for each component, indicating the size and location of surface and sub-surface defects. The DIRA-GREEN system is suitable for small and fragile metal injection moulding as well as PM parts thanks to a dedicated mechanical subsystem allowing their manipulation. The inspected parts enter a lead chamber used for X-ray radiation protection. Through a dedicated graphical user interface, users have point-and-click control over the motion management subsystem from a host computer. A microfocus X-ray source generates digital images of even very small sized parts. Exposure times can be less than a second. The part images are subsequently automatically evaluated by a specially developed defect detection software. This compares the recorded images to images of a perfect part and identifies any discrepancies. The DIRA-GREEN system for NDT of compacted parts produced by PM can help minimise porosities and microstructural cracks. The European PM industry with its many SMEs will be able to substantially increase its competitiveness through lower production costs and higher product qualities. Moreover, they can also tap into previously inaccessible markets.
Keywords
Digital radiography, powder metallurgy, green parts, non-destructive testing, small and medium-sized enterprises
