高能机械加工表面纳米化40Cr钢组织结构与力学性能

利用超声高能机械加工处理工艺在40Cr钢表面制备了纳米晶表面层。采用SEM,TEM和纳米压痕技术等分析了表面纳米晶层的组织结构与力学性能。实验结果表明,表面是由分布均匀的纳米级铁素体和纳米级渗碳体晶粒构成的复合纳米结构,过渡区由纳米级的渗碳体晶粒和粗晶铁素体晶粒构成。表面平均晶粒尺寸为3nm。随着深度的增加,晶粒尺寸逐渐增大。表面硬度高达8GPa,为基体硬度的3倍,随着深度的增加,硬度迅速降低。表面层弹性模量为252GPa,与基体十分接近。

Microstructure and mechanical properties of 40Cr steel nano-crystallized surface after high energy peening

Nano-crystallization surface on 40Cr steel was obtained by ultrasonic high energy peening treatment. SEM, TEM and nano-indention techniques were used to analyse microstructure and mechanical properties. Experimental results show that nano-crystallization surface is a mixture composed by homogeneous dispersing nano-sized ferrite grains and nano-sized cementite grains. Transition region under nano-crystallization surface is composed by nano-sized cementite grains and micro sized ferrite grains. Average diameter of grains on nano-crystallization surface is about 3nm, and gradually increases as depth increased from surface. Hardness of nano-crystallization surface is high up to 8GPa, which is more than 3 times of the matrix, and drops sharply as depth increased from surface. Modulus of nano-crystallization surface, 252GPa, is much close to that of the matrix.