1 Experimental Temperature Dependence of Stress-Elongation, Young’s Modulus and Fracture Stress for two Max Phase Bulk Materials C. Sylwan* 1 , S. Reichardt and T. Eriksson Royal Institute of Technology - KTH, Teknikringen 42, SE-100 44 Stockholm, Sweden Abstract. A recently discovered material, the Max phases, has properties between metals and ceramics. In order to judge their usefulness for achieving higher temperatures in the hot zones in gas turbines, some mechanical properties have been determined at various temperatures. The stress for 0.2% elongation, Young’s modulus and fracture stresses were calculated from stretch tests over the temperature range 22-1400 ºC. The Max phases were Maxthal 211 with and without niobium addition. In some regions comparisons were made with Inconel. The Young modulus was calculated by equation fitting from the elongation curves at several temperatures. Keywords: Young’s modulus, fracture stresses, Maxthal, Maxphases, rods, stress-elongation, creep specimen, surface study Introduction. This work is the core part of the Mistra-financed project “Fundamental study on the use of Max phases as material in micro turbines”, carried out at KTH by the Departments of Chemical Engineering Technology (KET), Chemical Technology (KT) and Heat and Power Technology (EGI). The project main goal was to investigate the possibility to employ Maxthal, Ti2AlC (211) titanium aluminium carbide and Ti2AlC + Nb (211Nb) consisting of niobium-doped titanium aluminium carbide, two newly discovered ceramic materials in gas turbines. Today, super alloys are usually used in high-temperature locations in gas turbines, interlaced with some sophisticated internal cooling designs. Static parts in the hottest places, e.g. guiding vanes without cooling air, would allow the turbine to run hotter with increased average engine temperature which, according to the Carnot rule, would lead to improved turbine efficiency. Based on 40 recorded, out of about 50 in all, stress-elongation tests at Swerea Kimab, at temperatures of 22 to 1400 ºC, stress for 0.2% elongation, Young’s modulus and also fracture stresses were studied. Our findings from these experiments were used for estimation of how well Maxthal could fit into turbines. Specimens. The test pieces were rods made of bulk material manufactured and supplied by Kanthal AB in Hallstahammar, Sweden. The bulk material was then machined into two different sizes of test rods which subsequently were stretch tested at several temperatures at Swerea Kimab in Stockholm, Sweden. The two different sizes were 7mm TMF rods, length 130mm, and SIMR creep specimen SK 25, which is 5mm across in the centre part and has a length of 50 mm. Since the material was scarce by the time the tests were performed, the rod sizes were chosen so that the two 10 mm diametre ends of a ruptured large rod could be utilized for the manufacture of two small rods and hence the material in a large rod could be tested three times. 1 *Corresponding author: [email protected]
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Experimental Temperature Dependence of Stress-Elongation, Young’s
Modulus and Fracture Stress for two Max Phase Bulk Materials
C. Sylwan*1, S. Reichardt and T. Eriksson
Royal Institute of Technology - KTH, Teknikringen 42, SE-100 44 Stockholm,
Sweden
Abstract.
A recently discovered material, the Max phases, has properties between metals and ceramics.
In order to judge their usefulness for achieving higher temperatures in the hot zones in gas
turbines, some mechanical properties have been determined at various temperatures. The
stress for 0.2% elongation, Young’s modulus and fracture stresses were calculated from
stretch tests over the temperature range 22-1400 ºC.
The Max phases were Maxthal 211 with and without niobium addition. In some regions
comparisons were made with Inconel. The Young modulus was calculated by equation fitting
from the elongation curves at several temperatures.