Sharif Digital Repository

In the present work, co-sintering of various powder injection molding (PIM) feedstocks including iron, low-alloy steels, high-alloy steels, and hardmetals was investigated. Dilatometric analysis was used to evaluate the sintering behaviour of co-injection moulded feedstocks after debinding. An approach based on the data of dimensional change versus time and temperature was proposed to determine the compatibility of two materials system for the two component powder injection molding (2C-PIM) process. The similarity of sintering behaviour of the twobody parts produced by 2C-PIM was quantified trough definition of a parameter termed as Apparent Co-Sintering Index (ACSI). The results determined... 

This paper reports co-sintering response of nanostructured WC-Co/316L stainless steel composite produced by assembling of powder injection molding (PIM) parts. A significant mismatch sintering shrinkage (>4%) was observed in the temperature range of 1080-1350 °C. The reaction between WC and Fe at the contact area resulted in the diffusion of C and Co into the iron lattice and eventually formation of a low-temperature liquid phase that in fact affects the shape control of the PIM parts during sintering. In order to make the co-sintering feasible, a special sintering cycle was developed. The reaction between the cemented carbide and stainless steel was also retarded by developing a special... 

Manufacturing of complex-shaped bimetals utilizing two-color powder injection molding (2C-PIM) and three-dimensional printing (3DP) processes, which basically involve sintering of a powder/binder mixture, has been attracted a great interest. This article addresses sintering of biocompatible Co-Cr-Mo alloy for manufacturing stepwise porosity-graded composite structures. Such composite structures provide strength at the core and a porous layer for the tissue growth. To evaluate the process, two grades of gas atomized Co-Cr-Mo powder with an average particle size of 19 and 63 μm were used. Isothermal and nonisothermal sintering behavior of the loose powders under hydrogen and argon atmospheres... 

An experimental rheological study has been performed to evaluate the influence of TiC addition on the rheological behavior and stability of 316L stainless steel powder injection molding (PIM) feedstock. The effects of TiC concentration, solid loading, shear rate and temperature were investigated via capillary rheometer method. The stability of feedstocks was evaluated quantitatively using "instability index", which describes the threshold beyond which the variation of viscosity becomes unacceptable for PIM purposes. The results show that the rheological behavior of PIM feedstocks highly depends on the blend composition. The addition of TiC particles to the stainless steel powder increases... 

Sintering response and phase formation during sintering of WC-Co/316L stainless steel composites produced by assembling of powder injection molding (PIM) parts were studied. It is shown that during cosintering a significant mismatch strain (>4 pct) is developed in the temperature range of 1080 °C to 1350 °C. This mismatch strain induces biaxial stresses at the interface, leading to interface delamination. Experimental results revealed that sintering at a heating rate of 20 K/min could be used to decrease the mismatch strain to <2 pct. Meanwhile, WC is decomposed at the contact area and the diffusion of C and Co into the iron lattice results in the formation of a liquid and MC and M6C... 

Recently, co-powder injection molding process (2C-PIM) has attained considerable interest to fabricate complex-shaped functional materials. The aim of this work is to study the sintering compatibility between nanocrystalline yttria-stabilized zirconia (3Y-TZP) and PIM grade 430L stainless steel (SS) powders, which is the utmost important step in the 2C-PIM process. To evaluate the mismatch strain development during the co-sintering, the isothermal and nonisothermal behaviors of the ceramic and metal powders were studied. Small bilayers of 3Y-TZP/430L were made by a powder metallurgy technique and the feasibility of simultaneous sintering and joining of the composite layer was examined....