Effect Of Heat Treatment Process And Ta Content On Microstructure And Properties Of9Cr-ODS/RAFM Steel

The performance parameter and evolution of Reduced Activated Ferritic/Martensitic(RAFM) steel was introduced in this paper firstly. Then a detailed overview of theapplication of oxide dispersion strengthened technology and heat treatment in RAFM steelwas presented. And the effect of Ta on the RAFM steel and the stability of TaC intempering was introduced. Based on all the above, the objective, content and technicalroute of this paper was put forward.The effect of sintering temperature on the microstructure and properties of the9Cr ODS/RAFM steel was studied. The sintering temperature ranged from1330℃to1410℃, according to the phase diagram of the Fe Cr. Alloy was sintered at1330°C,1360℃,1390℃,1410℃respectively. The results showed that the relative density,tensile strength, elongation, and microhardness increased at first then decreased with thesintering temperature increasing. The grains were finest and most uniform and the secondphases precipitated up to the most diffuse distribution when alloy was sintered at1390℃. The mechanical properties of the alloy decreased when the sintering temperatureincreased to1410℃.The effect of the quenching speed on the microstructure and properties of the9Cr ODS/RAFM steel was also studied.The alloys were austenitized at1150℃for1hand then quenched by three different quenching speed, which were air cooling, waterquenching and10wt.%NaCl brine quenching respectively, and finally tempered at750℃for1.5h.The results showed that the tensile strength and microhardness of the alloyincreased with the increase in speed of the quenching. The alloy grain refinedsignificantly and the MC type carbide precipitated more by brine quenching. The M23C6dissolved during tempering section which promoted the precipitation of MC type carbide.Finally, the effect of Ta content on the microstructure and properties of the9Cr ODS/RAFM steel was studied. The alloys with Ta content of0.10wt%,0.15wt%,0.18wt%and0.30wt%were prepared by sintering at1390℃and brine quenching. Theresults showed that the relative density, tensile strength, elongation, and microhardness of the alloy increased first and then decreased with the increase of the Ta content. The alloywith Ta content of0.18wt.%exhibited optimal mechanical properties that the tensilestrength was632MPa, the elongation was24.2%and the microhardness was343HV. Thiscan be ascribed to the finer and more uniform microstructure. Besides, a large amount ofsecondary precipitations of ultrafine TaC particles distributed in grains homogeneously.The mechanical properties of the alloy decreased little when it was tensiled at300℃because TaC kept stability and the dispersion strengthening was still excellent under hightemperature conditions. The tensile strength and elongation were570MPa and23.1%respectively at300℃.