Ceramic composite components with gradient porosity by powder injection moulding

Various components used in the industries may benefit from having layered structures with gradient porosity in each layer. In this paper, bi-layer composite components with gradient porosity made by Powder Injection Moulding (PIM) have been investigated. The ceramic spinel materials of AR7845 having coarse particle size and AR7820 having fine particle size were used. It shows that AR7820 and AR7845 powders have different sintering behaviour with the fine powder having faster shrinkage as compared to coarse powder. Curling or bending is found in the bi-layer rectangular composite component fabricated from these two powders. This is due to induced stress caused mainly by strain rate mismatch of the two materials during sintering. The degree of curling is also related to thickness ratio of two materials in each layer. Composite components can be designed into cylindrical shape so as to avoid curling as observed in rectangular composite components. No interfacial debonding and part cracking are observed in both rectangular and cylindrical composite components. The microstructure shows that continuously straight joining lines along the interfaces are formed in these composite components. Bi-layer composite components with combined properties of gradient porosity can be achieved by sintering them at different temperatures. (C) 2009 Elsevier Ltd. All rights reserved.