High temperature mechanical behavior of advanced directionally solidified multi-phase Mo-alloys with and without coating (HTMA-DS Mo)

• Applicants: Professorin Dr.-Ing. Manja Krüger; Professor Dr. Michael Scheffler
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Synthesis and Properties of Functional Materials
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 438070774

Mo-Hf-B and Mo-Zr-B alloys as a new class of refractory alloys are potential candidates in stationary and mobile turbine applications. Due to the high melting points of the constituents high-temperature strength and creep strength are expected up to 1,400 °C. Those high service temperatures, in turn, may result in higher turbine efficiencies and may reduce primary energy consumption.As a manufacturing route, directional solidification via zone melting as a new processing approach for Mo-Hf-B and Mo-Zr-B results in low oxygen (< 50 ppm) impurities, which is essential to avoid embrittlement of these alloys; moreover the materials possess a homogeneous fibre-reinforced microstructure.Aim of this proposal is to investigate the high-temperature creep behaviour of this novel class of refractory alloys to qualify them for high-temperature applications. While creep test data are available from experiments under compression, no data of creep under tensile load and under real service conditions are available for this type of alloys. Thus, our experimental research will divide into three parts: i) Sample preparation via directional solidification in a zone melting process, carried out at Kiev Polytechnical Institute KPI, and microstructure and phase composition characterization of the fibre-reinforced Mo-Hf-B and Mo-Zr-B alloys at KPI and at the Otto-von-Guericke University, Magdeburg, OVGU. ii) Creep tests will be carried out at OVGU under inert atmosphere and under real service conditions. For the later an oxidation protection coating must be provided due to oxidation and evaporation of molybdenum from the alloys. For this, iii) an oxidation protection coating strategy will be developed based on particle loaded preceramic polymers, and tensile creep behaviour will be characterized for coated alloys in oxidizing atmosphere. From these results we will a) develop a creep model for this novel-type material class and b) a coating model for molybdenum based refractory alloys.

• DFG Programme: Research Grants
• International Connection: Ukraine
• Co-Investigators: Dr.-Ing. Volodymyr Bolbut; Dr. Iryna Smokovych
• International Co-Applicant: Dr. Iurii Bogomol