新型9Cr-1Mo钢搅拌摩擦焊接头组织及性能

Microstructure and mechanical properties of friction stir welded novel 9Cr-1Mo steel

采用钨铼合金搅拌工具对新型9Cr-1Mo钢进行搅拌摩擦焊工艺试验,探讨焊缝成形、组织及性能变化规律.结果表明,在300和400 r/min的转速,50 mm/min的焊接速度下可获得无缺陷接头;焊缝主要由搅拌区和热力影响区组成,具有明显的马氏体淬硬组织特征;高温热影响区为淬硬马氏体和回火马氏体混合组织,低温热影响区为过回火马氏体组织.焊缝区具有晶粒细化特征,其晶粒尺寸约为母材69.2%.焊缝区产生明显硬化,最高硬度约为母材硬度值的2.0倍.焊接接头抗拉强度达到母材98%以上,搅拌区和热影响区冲击吸收能量分别达到母材的77.8%和87.4%,表明搅拌摩擦焊接头仍具有较好强韧匹配.

The novel 9Cr-1Mo ferritic heat-resistant steel was selected to conduct friction stir welding experiment adopted tungsten-rhenium alloy tools, and the variation laws of weld formation, microstructure and mechanical properties were discussed. The results indicated that no defect welded joints could be obtained with the rotation speed of 300 and 400 r/min, and welding speed of 50 mm/min;the weld zone was mainly composed of stir zone and thermomechanical affected zone, which had obvious characteristics of hardened martensite microstructure;the high temperature heat affected zone presented mixed microstructures of hardened martensite and tempered martensite, and the low temperature heat affected zone showed over tempered martensite. The grains in the stir zone were refined and the average grain size of the stir zone was about 69.2% of that of the base metal. The weld zone had been significantly hardened, and the maximum hardness in the weld zone was more than 2.0 times of that of the base metal. The ultimate tensile strength of the welded joint reached about 98% of that of the base metal, and the V-shaped notched impact absorbed energy of the stir zone and heat affected zone reached 77.8% and 87.4% of that of the base metal respectively. Those results indicated that the friction stir welded joint still has the better matching between strength and toughness.