Microstructure and mechanical properties of molybdenum-titaniumzirconium-carbon alloy TZM processed via laser powder-bed fusion

L. Kaserer*, J. Braun, J. Stajkovic, Karl-Heinz Leitz, P. Singer, Ilse Letofsky-Papst, Heinrich Kestler, G. Leichtfried

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Molybdenum, processed by laser powder-bed fusion (LPBF), is susceptible to hot cracking because segregated oxygen impurities significantly weaken grain boundaries through the formation of MoO 2. The present study reports on the LPBF processing of the most important molybdenum alloy TZM, whose alloying elements—titanium, zirconium, and carbon—lead to particle and solid solution strengthening. Results of investigations into the resulting microstructure and mechanical properties when processing TZM by LPBF are presented. The alloying elements suppress the segregation of oxygen to the grain boundaries so that crack-free samples with a density of 99.7 ± 0.3% may be produced. The microstructure shows grains that are columnar due to epitaxial grain growth and a weak 〈111〉 fiber texture parallel to the building direction. Mo 2C and ZrO 2 particles with a size of <50 nm are precipitated in the grain interior. Oxygen is not only bound by ZrO 2. Research has shown that the ternary molybdenum‑titanium carbide, which can be found in LPBF – TZM – as is the case with pressed/sintered TZM—can dissolve oxygen. While the bending strength is 591 ± 26 MPa for samples in which only pores with a diameter of <50 μm could be detected on the fracture surface, the bending strength drops to 267 ± 50 MPa for samples with defects of 400 μm. In both cases, the fracture mode is transgranular brittle.

Original languageEnglish
Article number105369
Number of pages7
JournalInternational Journal of Refractory Metals & Hard Materials
Volume93
DOIs
Publication statusPublished - 2020

Keywords

  • Laser powder-bed fusion
  • Mechanical properties
  • Microstructure
  • Molybdenum
  • TZM

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Ceramics and Composites
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Fields of Expertise

  • Advanced Materials Science

Treatment code (Nähere Zuordnung)

  • Basic - Fundamental (Grundlagenforschung)

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