Reduction of the embrittlement effect of binder contamination in MIM processing of Ti alloys

ABSTRACT

During metal injection moulding (MIM) processing, titanium tends to react with carbon from the polymeric binder. Thus, carbides, which can effect embrittlement, might be formed if the carbon solubility of the alloy is exceeded. Especially in β-titanium alloys, this is a critical issue, because β-phase stabilising elements like V, Mo and Nb decrease the carbon solubility of the Ti-matrix. This study summarises studies with different approaches to limit carbide precipitation in a Ti–22wt-%Nb alloy processed by MIM. Adding Zr led to a significant reduction in the amount and size of carbides due to an increase in the lattice constant. Furthermore, boron was added supporting a finer distribution of the carbides. Scanning electron microscopy and transmission electron microscopy investigations reveal the role of the elemental additions and analyse the structure of the different carbides formed. Combinations with heat treatments led to significant reduction in the amount of carbides.

KEYWORDS:

• Metal injection moulding
• β-titanium alloys
• carbide reduction
• lattice widening
• heat treatment

Notes on contributors

Thomas Ebel studied Physics at Hamburg University, Germany, and got his PhD degree in the field of materials science. After doctorate and post-doc time, he worked 10 years as a developer in a private medical company. He was mainly involved in materials development, application and processing and started to work on MIM of titanium alloys. Since 2006, he has been the head of department in the Institute of Materials Research of the Helmholtz-Zentrum Geesthacht. His main working topic is powder metallurgy (P/M) of titanium and magnesium aiming, in particular, at the development of dedicated P/M alloys optimised for processing and application.

Tobias Beißig is now a development engineer at WaveLight GmbH and is working in the Department of Research and Development of diagnostic devices for cataract surgeries. He contributed his results within the framework of his master thesis in Medical Engineering at the Technical University of Berlin. For his bachelor thesis at the Brandenburg University of Technology Cottbus, he investigated TiAl alloys with high tantalum content for high temperature applications.

Sandra Ebner studied Materials Science at the Montanuniversität Leoben, Austria, and submitted Diploma thesis on MIM Ti–Nb alloys for biomedical applications in cooperation with the Helmholtz-Zentrum Geesthacht. Since September 2016, Sandra Ebner is pursuing PhD on AHSS steels at the Montanuniversität Leoben.

Xia Luo has been a lecturer from the School of Materials Science and Engineering, Southwest Petroleum University since 2016 and studied Materials Processing at South China University of Technology (SCUT). Xia Luo obtained PhD in Materials Science (semi-solid powder processing) and has 6 years of research experience in powder metallurgy of aluminium and titanium alloys.

Anok Babu Nagaram obtained Bachelors of Engineering in Mechanical Engineering in 2009 at Osmania University, India. He received his first Master’s degree in Materials Science and Engineering in 2011 at the National Institute of Technology, Trichy, India. He obtained his second Master's degree in Materials Science in 2015 at the Technical University of Darmstadt, Germany. His main area of interest is powder metallurgy of metallic materials. He worked as a research assistant at Helmholtz-Zentrum Geesthacht, Germany, from January 2015 to September 2015 on topic ‘Effect of Zirconium on Ti–22Nb alloy processed by Metal Injection Moulding (MIM) for Biomedical Applications’.

Dapeng Zhao is an assistant professor at the College of Biology, Hunan University (China). He received his PhD in Materials Science from the Brandenburg University of Technology Cottbus-Senftenberg (Germany) in 2014. His current research interests are primarily in the fabrication and surface modification of titanium- and magnesium-based materials for biomedical applications. He is currently the principal investigator for a research project funded by the National Natural Science Foundation of China (No. 51604104).

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Dapeng Zhao http://orcid.org/0000-0001-6777-7760