Pressure-affected flow properties of powder injection moulding compounds

Abstract

The effect of pressure and temperature on the flow properties of the materials intended for Powder Injection Moulding (PIM) technology was studied using a single-piston capillary rheometer modified by additional backpressure chamber. The influence of pressure and temperature on shear viscosity has been quantified through pressure and temperature sensitivity coefficients derived from Carreau-Yasuda model. The temperature sensitivity of the 50 vol.% compound based on cemented carbide powder is lower than that of pure polymeric binder, and it varies only slightly with pressure. In contrast, the pressure sensitivity of compounds was found to be higher than that of pure polyolefin binder, and it is decreasing function of temperature. In addition, it is shown that temperature sensitivity of binder, which is considerably enhanced by pressure (in contrast to the PIM demands), cannot be determined as being equal to the properties of particular binder components.

The effect of powder characteristics on pressure sensitivity of powder injection moulding compounds

“…This was confirmed for the low to moderate (up to 30vol.%) powder loadings in our previous paper [21]. Nevertheless, at higher loading levels (flow complicated by the onset of instabilities) sensitivity to pressure seems to be enhanced comparing to a pure polymer binder [22]. In order to confirm this idea the following contribution examines three types of compounds differing in the powder characteristics, whose flow is stable in the broad range of shear rates.…”

“…As introduced by Sedlacek et al [23], and described in detail in our previous paper [22], the rheometer was modified with an additional device generating backpressure, which causes increase of pressure actuating on the tested materials, Fig. 3.…”

Powder Injection Moulding - An Alternative Processing Method for Automotive Items

“…The activation energy of carbide compounds decreased with powder content, indicating a decay of the sensitivity of a compound to temperature changes. Hausnerova et al (2009), employed another approach to determine temperature sensitivity of PIM compounds and reached the same conclusion. Very recently, Contreras et al (2010) broaden this finding for a set of three bronze and four Inconel 718 powders.…”

Effect of carbide powder characteristics on the PVT behavior of powder injection molding compounds

“…As we have shown recently [10][11][12] in the papers reporting pressure and temperature dependent flow properties of cemented carbide compounds, it is not only powder loading, but also powder particle size distribution and mean particle size influencing considerably a bulk compressibility of PIM compounds. Therefore, the aim of this research is to evaluate the influence of such powder parameters on pressurevolume-temperature behavior of PIM compounds.…”