Research On Microstructure And Properties Of9Cr-ODS/RAFM First Wall Blanket Structural Material Prepared By PM

The performance parameter and evolution of Reduced ActivatedFerritic/Martensitic（RAFM） steel have been firstly introduced in this paper. Then a detailedoverview of the application of oxide dispersion strengthened technology and heat treatmentin RAFM steel was presented. Moreover, a brief introduction on Spark PlasmaSintering（SPS） was exhibited. Based on all the above, the objective, content and technicalroute of this paper was put forward.Effect of ball milling process, compacting process and sintering process on themicrostructure and properties of9Cr-ODS/RAFM steel prepared by mechanical alloying+vacuum sintering were studied. Results showed thatFe–9Cr–1.5W–0.4Mn–0.4Ti–0.2Si–0.2V–0.1Ta–0.1C–0.3Y₂O₃powder could be basicallyrealized alloying after48h ball milling, under the condition of220r/min,20:1ball/powderratio（BPR）, no progress control agent. However, the powder yield was rather low using theabove ball milling progress. On that basis, the original ball milling progress was changed toM1progress which added2wt%stearic acid into the powder obtained by original ballmilling progress and then milled for another two hours. High alloying powder could beobtained by using M1ball milling progress. The porosity and bending strength of green bodycompacted by one-way moulded forming showed small changes when compacting pressureexceeded700MPa. With the increasing sintering temperature, the mechanical properties of9Cr-ODS/RAFM steel were improved, and9Cr-ODS/RAFM steel sintered at1390℃exhibited optimal mechanical properties （tensile strength:600MPa, elongation:23.1%）.Rising the sintering temperature continuously, a sudden drop in mechanical properties wasobserved.Effect of Y₂O₃and sintering temperature on microstructure and mechanical propertieswere studied in this paper. Results showed that the tensile strength and elongation of ODSsamples containing0.3wt%Y₂O₃as additive were higher than Non-ODS samples withoutY₂O₃in each sintering temperature. Optimal mechanical properties could be obtained whensintering temperature reached1390℃,1360℃for Non-ODS samples and ODS samples respectively. At optimal sintering temperature,the tensile strength and elongation of ODSsamples were600MPa,23.1%, while Non-ODS samples were470MPa,12%. Themicrostructure of9Cr-ODS/RAFM steels were martensit, ferrite, M₂₃C₆, and Y-Ta-Ocompound （white core-black rim phase）. EDS analysis results indicated that core were richin Y, Ta, O elements, while rim were rich in Cr, V, Ti elements. From the consideration ofthermodynamics, Cr/V/Ti rim could make contribution to wetting which promoted theformation of Y₂O₃based phase, and then improved the mechanical properties of RAFMsteels. Poor performance of Non-ODS samples might resulted from the existence of a largenumber of uniformly ultrafine TaC particles in grain boundary, whose hardness was muchhigher than matrix. Therefore, Ta addition should be controlled in RAFM steels, and furtherstudy needed to be carried on obtain optimal Ta addition.The influence of heat treatment on the microstructure and mechanical properties of9Cr-ODS/RAFM steels were studied in this paper. The experimental results showed thatY₂O₃had not only the effect of grain refinement, but also better structure stability. The Ac1and Ac3temperature for9Cr-ODS/RAFM steel are measured as851.3℃and955.01℃.Itwas suggested that the ideal heat treatment for9Cr-ODS/RAFM steels would be: heattreatment at1160℃followed by water cooling or other fast cooling method and tempering at760℃.The microstructure and mechanical properties of9Cr-ODS/RAFM steels fabricated bysps process had been exploratory researched. The experimental results indicated that SPSsamples sintered at1200℃exhibited single matrix microstructure riched in Fe, Cr, W, Ti, Celements. The hardness of SPS samples were4-5times higher than MA-Vacuum samples.