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!