Advanced material development : functionally graded stainless steel alloy composites

D.Ing. (Mechanical Engineering)Abstract: Laser metal deposition (LMD) is one of the additive manufacturing technologies that is used in the production of fully dense parts layer by layer. This innovative manufacturing process shows real promise in reducing component fabrication time, cost and weight. One of the major advantages of this technology is in the ability to manufacture components with multi-material properties such as Functionally Graded Materials (FGM). FGM is a class of advanced materials that combine the benefits of its component materials together as a whole, while minimizing the problems produced by material property mismatch of the constituent materials. Several studies have been conducted on FGMs processed by LMD. Most of these studies are on metal-ceramic composites, however, there is a growing need for bimetallic components with different properties along their axial or radial directions for modern engineering applications. In this study, the laser metal deposition process was evaluated as a candidate for manufacturing a compositionally graded bimetal material consisting magnetic and non-magnetic metals. The materials used were 17-4PH powder, AISI 316L powder and AISI 316 substrate. Since this study has not been done and there were no known models or strategies to follow in building this particular FGM. Trial and error experiments were first adopted in selecting the process conditions for building the FGM. The trial and error experiments, referred to as preliminary study involved the production of 17- 4PH and AISI 316L clads. This was done primarily to evaluate the solidification behaviour of the individual powders and also identify the process window that will successfully produce fully dense clads with good bonding and wettability that are structurally harmonised. Based on the findings of the preliminary studies, a set of parameters was obtained as a standard for producing the compositionally graded composite..