Improvement in High Temperature Fatigue Strength of Industrial Oxide Dispersion Strengthened Platinum with Formation of Stretched Coarse Grain Structure

Abstract

Platinum and its alloys are widely used for glass melting apparatus and the materials used for the apparatus require high temperature fatigue strength as well as high temperature creep strength. Authors reported that Oxide Dispersion Strengthened (ODS) Platinum has high resistance to creep rupture in the previous paper. In order to clarify the details of fatigue fracture behaviors of ODS Platinum, various ODS Platinum materials were evaluated with regard to tensile and fatigue tests. Through the evaluations, following results were obtained. (1) High fatigue strength results in short inter-dispersoid distance in low cycle region and high Grain Aspect Ratio (GAR) in high cycle region. (2) Fracture mode of low GAR material is trans-granular fracture in low cycle region and inter-granular fracture in high cycle region. Different from low GAR material, fracture mode of high GAR material is trans-granular fracture for both low and high cycle region. (3) High temperature fatigue strength of ODS Platinum in low cycle region is in inverse proportion to the inter-dispersoid distance as well as high temperature tensile strength. An increasing in OROWAN stress is a measure to improve the strength in the low cycle region. In the high cycle region, fatigue strength is in proportion to GAR therefore increasing in GAR is a measure to improve the strength in the region.