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

Mo-Hf-B和Mo-Zr-B合金作为一种新型的耐火合金，在固定式和移动的涡轮机中有着潜在的应用前景。由于组分的高熔点，高温强度和蠕变强度预计高达1，400 °C。作为一种制造方法，通过区域熔化的定向凝固作为Mo-Hf-B和Mo-Zr-B的一种新的加工方法，（< 50 ppm）杂质，其对于避免这些合金的脆化是必要的;此外，该材料具有均匀的纤维增强的微观结构。该提案的目的是研究这种新型耐火合金的高温蠕变行为，以使其有资格用于高温应用。虽然蠕变试验数据可从压缩下的实验中获得，但对于这种类型的合金，没有拉伸载荷下和真实的使用条件下的蠕变数据。因此，我们的实验研究将分为三个部分：i）在基辅理工学院KPI进行的区域熔化过程中通过定向凝固制备样品，以及在KPI和位于马格德堡的奥托-冯-格里克大学OVGU进行的纤维增强Mo-Hf-B和Mo-Zr-B合金的微观结构和相组成表征。ii）蠕变试验将在惰性气氛和真实的使用条件下在OVGU进行。对于后者，由于钼从合金中的氧化和蒸发，必须提供氧化保护涂层。为此，iii）将基于颗粒加载的陶瓷前体聚合物开发氧化保护涂层策略，并且将表征涂层合金在氧化气氛中的拉伸蠕变行为。根据这些结果，我们将a）开发这种新型材料类别的蠕变模型和B）钼基耐火合金的涂层模型。

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.