Characterization of Nanocrystallizatin Surface Layer of 0.4C-1Cr Low Alloy Steel Prepared by Ultrasonic Particulate Peening

A nanostructured surface layer was fabricated in a quenched and tempered 0.4C-lCr low alloy steel by ultrasonic particulate peening technique. The microstructure of the nanocrystalline surface layer was characterized by means of TEM and Mossbauer spectroscopy. Experimental results reveal that both cementite and ferrite nanocrystals with an average size of 5 nm were formed in the surface layer of the steel, phase transformation of austenite and dissolution of cementite maybe occur in the process of ultrasonic paniculate peening.

Surface morphology and mechanical properties of the nanocrystalline tensile-straightening rollers treated by the ultrasonic particulate peening

Tensile-straightening rollers of a pickling line at Baosteel are surface nanocrystallined by the ultrasonic particulate peening(USPP)method.Surface morphology and mechanical properties of the rollers were characterized by scanning electronic microscope(SEM),a roughness meter and a microhardness tester.Results have indicated that there are a lot of randomly distributed impact pits on the surface after the USPP and that surface roughness can be adjusted within a range of Ra 1.5-2.5.The grain size in the surface layer is refined significantly.The microhardness of the surface layer can reach 920 HV after the nanocrystalline treatment.The dependency of the two main influencing factors,i.e.the working gas temperature and pressure,on the surface roughness and microhardness is presented.

超音速微粒轰击纳米化拉矫辊表面形貌与力学性能研究

采用超音速微粒轰击方法（USPP）对宝钢某机组拉矫辊进行了表面纳米化处理,利用扫描电镜（SEM）、粗糙度仪和显微硬度计对其表面形貌和力学性能进行了表征分析,结果表明,轰击后拉矫辊表面随机分布大量的冲击坑,表面粗糙度可在1.5-2.5之间调整;拉矫辊表层晶粒尺寸明显细化。纳米化处理后拉矫辊表层硬度可达到HV 920。工作气体温度和压力是影响酸洗拉矫辊表面粗糙度和显微硬度的主要因素。

超音速微粒轰击表面纳米强化多通道喷嘴气固双相流的数值模拟

采用气固双相流模型(离散相模型)研究了超音速微粒轰击表面纳米强化多通道耦合喷嘴的流场,通过计算,分析了气固两相速度场以及固体颗粒在气体流场中的轨迹。模拟结果发现,气体—颗粒双相射流中,气固两相射流速度均可以达到超音速,而且颗粒相的分散度小于气体,粒径小于5μm的颗粒相其分散度随颗粒粒径增大而减小,大于5μm的颗粒相其射流分散度基本稳定,颗粒相粒子集中在各通道射流中心线附近。最佳表面纳米强化处理距离在120 mm附近。模拟结果有助于设计面向大规模表面纳米强化处理应用的多通道耦合喷嘴。