PSI - Issue 19

Akifumi Niwa et al. / Procedia Structural Integrity 19 (2019) 106–112 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Platinum alloys are widely used in industrial applications, such as fuel cell electrodes and catalysts for removing harmful substances contained in automobile exhaust gas [1]. On the other hand, also in the glass industry, it has been widely used in glass manufacturing process as members such as melting crucibles and stirrers because it has excellent corrosion resistance to molten glass at high temperature and has high oxidation resistance. In particular, recently the range of application continues to be expanded as the development of glass requiring hard to melt and high quality such as glass for LCD panels progresses. Since such glass is produced at higher temperatures, platinum alloys are required to have higher strength. Therefore, when such high strength is required, about 10 wt% of rhodium added solid solution strengthened platinum-rhodium alloy is used, and when even higher strength is required, oxide dispersion strengthened (ODS) platinum alloys have been developed and applied [2, 3]. In ODS platinum alloys, materials in which zirconium oxide particles are dispersed in platinum or platinum-rhodium alloy matrix are generally used, and the dispersed particles enhance high temperature strength and suppress grain growth and make it possible to have long-term stable characteristics [4]. On the other hand, since these members are very expensive, it is required to obtain the longest possible life with the least amount of usage, and the need for life improvement and life prediction is also significant from the aspect of production cost. However, although there are some studies on high temperature creep properties [4-6], there are few data on the mechanical properties like high temperature fatigue, or the interaction between creep and fatigue of these alloys [7]. Therefore, it is difficult to estimate the effect of axial stress due to the internal pressure by the molten glass and cyclic bending stress due to the rotation of the stirrer on the life of the platinum alloy container used in the stirring process. Therefore, in this study, zirconium oxide dispersion strengthened platinum 10% rhodium alloy which is actually used for a container in a stirring process was used as a test material. Then the bending fatigue test under axial stress at 1400 °C close to a practical environment was carried out, and acquisition of the fatigue characteristics and elucidation of the fracture mechanism were conducted. 2. Experimental

2.1. Materials

The test material is ODS platinum-10% rhodium alloy (FKS® Rigilit®; Umicore AG & Co. KG), and the physical properties are as shown in Table 1. For the test pieces, cut from 0.8 mm thickness sheet material by electrical discharge machining and a notch was introduced in the part where become high temperature during the test. After processing, all test pieces were annealed at 1300 °C for 1 hour to be ready for the test.

Table 1. Mechanical Properties of ODS Pt-10%Rh.

Fig. 1. Shape of specimen

2.2. High temperature bending fatigue test with axial stress Bending fatigue testing machine (PTF-160; TOKYO KOKI CO. LTD.) was used for the test. As shown in Fig. 2, one side of the test piece is subjected to a certain axial stress as a minimum tensile stress (σ min ) and the test was conducted with a stress waveform close to the practical environment by giving a cyclic bending stress amplitude (σ a ). At that time, the test piece is completely fixed by Jig B, but it is not restrained in the axial direction by Jig A since it