Effect of the Initial Precipitate States on the Creep and Creep Rupture Characteristics of 18-8 Ti Stainless Steel

Abstract

The initial precipitate states in 18-8 Ti stainless steel with variable precipitate amount and shapesare made by heat treatment and their effects on the creep and creep rupture characteristics are mainlyinvestigated. Hardness at room temperature and short time tensile test at high temperature are examinedfor comparision with creep strength. The microstructures from extracted replica and thin foilare observed by electron microscopy.
The creep characteristics are good represented for soluble Ti content (or soluble C content) and itis suggested that mutual action between soluble Ti and C is fairly great for creep strength. Moreover, the creep characteristics are strongly influenced by the initial precipitate states and this is discussedfrom the view points of mutual action between precipitates and dislocation. The needle type precipitate, which is assumed to be Cr₃C₂, is found to have the relation with the great decrease of creepstrength and its mechanism is discussed. It is observed that the effect of the initial precipitate stateson the hardness and short time tensile properties are very little.