Effect of Tantalum Content on Creep Properties of CLAM Steel

This paper presents the results of an experimental study about the effect of tantalum content on the creep properties of China low activation martensitic steel. Four heats of the steel with tantalum content ranging from 0.027 to 0.18 wt% have been fabricated and the creep tests have been carried out at 550 °C over a stress range of 230–240 MPa. The results indicated that the elevation of tantalum content caused an obvious increase in the rupture time of one order of magnitude and a dramatically decrease in creep rate for one order of magnitude. Both the creep rupture time and minimum creep rate revealed good linear relationships versus tantalum content on log–log scale, and empirical models were built up. The improvement of creep properties could be attribute to the change of microstructure caused by the increase of tantalum content. The microstructure observation indicated that the average grain size of the prior austenite decreased and the precipitation of Ta-riched MX was promoted with the addition of tantalum.