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Technical Briefs

Minimizing Contamination in Commercial Mass Production of Metal Injection Molded Pure Titanium

[+] Author and Article Information
P. Chalermkarnnon1

 National Metal and Materials Technology Center, 114 Thailand Science Park, Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120, Thailandprasertc@mtec.or.th

A. Manonukul

 National Metal and Materials Technology Center, 114 Thailand Science Park, Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120, Thailand

N. Muenya2

 National Metal and Materials Technology Center, 114 Thailand Science Park, Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120, Thailand

H. Nakayama, M. Fujiwara

 Castem Co., Ltd., 1808-1 Nakatsuhara, Miyuki-Cho, Fukuyama, Hiroshima 720-0004, Japan

1

Corresponding author.

2

Permanent address: 2/38 Moo 8 Soi 17 Rattanathibet Rd., Bang Krasor, Muang Nonthaburi, Nonthaburi 11100, Thailand.

J. Manuf. Sci. Eng 133(5), 054502 (Oct 12, 2011) (6 pages) doi:10.1115/1.4004945 History: Received December 07, 2010; Revised August 10, 2011; Published October 12, 2011; Online October 12, 2011

Metal injection molding (MIM) has been used in manufacturing highly complex metal parts but has had far less application for titanium which is a reactive metal. The implementation of titanium MIM on a mass production scale still raises many difficulties due to the contamination from processes, especially in case of manufacturing titanium parts on existing steel-based part production lines. The effects of material contamination in commercially-pure (CP) titanium parts have been studied and the trial production of titanium parts on a commercial MIM production line has been carried out. Steel-based feedstocks gathering on titanium green parts diffused into the titanium giving rise to liquid phase sintering, which disfigured the appearance of the titanium products. The trial production of titanium parts on a steel-based mass production line resulted in products with poor mechanical properties compared with those produced under laboratory conditions. The contamination by steel during the process resulted in the formation of a Ti–Fe solid solution phase at localized areas in the parts, decreasing the elongation to below 4%. Methods to reduce contamination in the mass production line have been carefully applied and acceptable properties, e.g., elongation about 18%, of titanium parts successfully achieved. CP titanium parts can be manufactured via well-controlled production in the steel-based MIM factory.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the MIM process for producing titanium part

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Figure 2

Titanium parts contaminated with common commercial steel-based feedstock at green and sintered stages

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Figure 3

Interdiffusion coefficients of Fe and Ti as a function of temperature [9]

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Figure 4

Binary phase diagram of Fe–Ti [10]

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Figure 5

Stress–strain curves of titanium specimens fabricated in (a) mass production environment and (b) laboratory environment

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Figure 6

Fracture surfaces of titanium specimen no. (a) M1 and (b) M2 fabricated in mass production line

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Figure 7

SEM images of (a) dull and (b) shiny areas on fracture surfaces of titanium specimen no. M1

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Figure 8

SEM images of fracture surface of titanium specimen no. M2 at several magnifications zooming into fracture origin

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Figure 9

EDX analysis of cleavage origin on fracture surface of titanium specimen no. M2

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Figure 10

EDX line-scan analysis of fracture surface of titanium specimen no. M2: (a) the line where scanned, (b) Ti component, and (c) Fe component

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Figure 11

Stress–strain curves of titanium specimens fabricated in well-controlled MIM production line

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