轴承钢GCr15高速冲击绝热剪切带的研究

摘要

In order to further understand the failure of wind turbine bearing and improve their service life, the failure mode of bearing steel GCr15 under dynamic load is presented and studied in this paper. Dynamic impact tests were conducted in GCr15 by using the Split Hopkinson Pressure Bar. The formation mechanism of adiabatic shear bands ( ASBs) and microstructural evolution were investigated by using optical microscope, SEM and FIB/TEM. The results show that compact ASBs were produced in GCr15 and cracks were formed along ASBs under impact loading. Grains were severely refined in ASBs and the ASBs were consisted of substructures and nano-sized equiaxed grains. The existence of massive dislocation defects in the subgrains in the core of the ASBs indicates that the grain refinement was dominated by dynamic recovery and incomplete dynamic recrystallization. The microhardness increased sharply at the core of ASBs due to the refined grains.%为了加深对风机轴承失效的进一步理解,从而提高其服役寿命,本文提出并研究了轴承钢GCr15在动载荷下的失效模式,采用分离式霍普金森压杆(SHPB)对轴承钢GCr15进行动态冲击试验,借助光学显微镜、SEM和FIB/TEM研究动态载荷下绝热剪切带的形成机理和组织变化.研究表明:冲击载荷下GCr15内部产生致密的绝热剪切带,且裂纹伴随着剪切带产生.剪切带中的晶粒被严重细化,由亚结构和纳米等轴晶组成.带中心部位大量位错缺陷的存在说明晶粒是在动态回复和不完全动态再结晶主导机制下逐步被细化的过程.细化的晶粒使得ASB内显微硬度值显著升高.