The Characterization and Rheological Investigation of Materials for Powder Injection Moulding / Ukwueze Bonaventure Emeka...[et al.]

Stainless steel and Zirconia have become an attractive choice of powder injection moulding (PIM) materials because of their respective excellent mechanical and thermal properties. These are often combined deliberately to produce functional graded components. The characterization and rheological investigations of the materials are thus indispensable for successful implementation of subsequent stages to the PIM process. In this investigation, the powder materials were characterized. Two feedstock with solid loadings of 68% for stainless steel (17-4PH) and 50% for 3mol% yttria stabilized zirconia (3YSZ), were prepared based on optimal loading of 3% lower than the critical value. A common binder was employed comprising of 60% palm stearin and 40% polyethylene. The rheological results for the two materials exhibited pseudo-plastic and shear thinning behaviour indicated by decrease in velocity with increasing shear rate. The results also show that a temperature of 1300C is considered appropriate for injection moulding of both feedstock

Two component injection moulding of bi-material of stainless steel and yttria stabilized zirconia – green part

The two component injection molding (2C-PIM) is a promising technique for production of small, complex and high density, metal-ceramic parts in large scales. This method is a viable option for integrating incompatible functions or properties of the materials in a singular part or component. Thus, the production of near net shaped components via 2C-PIM is imperative due to cost effectiveness resulting from high unit volumes. In this study, the feasibility of joining stainless steel (17-4PH) and 3mol% yttria stabilized zirconia (3YSZ) materials in their green states was investigated. Two feedstock of SS17-4PH and 3YSZ powder materials was prepared based on optimum solid loading of 3vol% lower than value of the critical loading. The critical solid loading for the SS17-4PH and 3YSZ powder materials were 71vol% and 53vol% respectively, based on the oil absorption technique ASTM: D-281-12. The binder system utilized comprises of 60wt.% palm stearin (PS) and 40wt.% low density polyethylene (LDPE). The two materials were injected sequentially using the screw type injection molding machine (BOY 22A) to form a bi-material component. The green properties were investigated. The morphology of the individual green parts and composites depicted that the powders were optimally dispersed in the binder matrix indicating good mixture and compaction of the green components. The flexural strength of the single components of the bi-material was above 5 MPa. The strength of the bonding zone which was 1.4 MPa indicates an evidence of bonding