reporter : ming-yeh chuang teacher : chen, cheng-ho date : 06/11/2015
TRANSCRIPT
Reporter:Ming-Yeh Chuang
Teacher: Chen, Cheng-Ho Date: 06/11/2015
2Introduction
Metal injection Moulding(MIM)
Low cost production
High material utilization
Mouldability The viscous flow of feedstock into the die cavity.Certain rheological
Ideal formulation The formulation of surfactant system.
Ti-MIM system The same binder composition
Powder A
Powder D
Powder C
Powder B
3Introduction
Common MIM binder system
Plasticizer (waxes)
Polymer
Surfactant
Metal powders BinderInteraction
Ex : Surface wetting, spreading, adsorption, binder strengthening
Powder injection moulding(PIM)
Stearic Acid
First choice in Ti-MIM
Suitable surfactant Excellent properties (also used for other PIM)
4
Argon gas atomized (GA) spherical CP-Ti powder
(particle size < 45 μm)
Polyethylene glycol (PEG)
Polymethyl methacrylate (PMMA)
Stearic acid
Peanut oil
Castor oil
Materials
Fig. 1. SEM micrograph of GA cp-Ti powder.
PEG
5Experimental
30 ml Acetone
Feedstock
83% PEG
15% PMMA
2% Surfactant
45 °C Stirring
Stirring220 rpm
Vacuum45°C
5 g
Ti powder
Acetone
SA = Feedstock APeanut oil = Feedstock BCastor oil = Feedstock C
6Results & discussion
Fig. 2. Shear stress versus shear rate graphs for feedstocks at 100 °C.
Yield stress ↓Plastic viscosity ↓
Lower pressure for moulding
7Results & discussion
Fig. 3. Yield stress dependence on temperature for different feedstocks. The decrease in yield stress with temperature is more prominent for feedstock containing SA (feedstock A).
PMMA soften
FlowabilityThe best moulding temp = 105 and 130°C
8Results & discussion
Fig. 4. Double logarithm of viscosity vs. shear rate plot for different feedstocks in the temperature range of 80–140 °C. It must be noted that due to extremely low viscosities of feedstock B and C, calculations at 140°C were not possible.
Higher shear sensitivityThan B and C.
9Results & discussion
Fig. 5. Double logarithm of viscosity vs. shear rate plot of different feedstocks at 120°C.
10Results & discussion
Fig. 6. Temperature dependence of viscosity for feedstocks in the temperature range of 80–130 °C at a shear rate of 1500 s-1.
11Results & discussion
12Results & discussion
Fig. 7. Fracture surface morphologies of Feedstock A (left) and Feedstock C (right).
13Results & discussion
14Results & discussion
Fig. 8. Comparison of chemical fromula of stearic acid (left) and castor oil (right). It should be kept in mind that castor oil is a combination of different fatty acids. However, ricinoleic, oleic and linoleic acids are the three main ingredients.
15Results & discussion
Fig. 9. Green strength comparison of two feedstocks.
16Conclusion
• Viscosity of feedstock is decreased using oil as surfactant, thereby a higher solid loading can be achieved.
• It is determined that feedstock containing castor oil as surfactant possessed a higher flexural strength and higher mouldability index value than feedstock containing stearic acid as surfactant.
• The improved properties are attributed to the more interaction between binder and titanium powder and better dispersion of the powder due to the presence of extra polar groups in castor oil molecule.
Thanks for your attention!