DD5缓进磨削表面粗糙度和硬化率对疲劳性能影响研究

Research on Influences of Surface Roughness and Hardening Rate on Fatigue Property in DD5 Creep Feed Grinding

为研究DD5镍基单晶高温合金缓进磨削表面粗糙度和硬化率对疲劳性能的影响规律及机理,设计实验并进行了试件磨削与疲劳性能测试。结果表明:表面粗糙度的增大引起应力集中加剧,导致疲劳性能降低,不同磨削工艺下表面粗糙度由0.347μm增大到0.687μm,其疲劳寿命由5.51×10^(5)降至3.38×10^(5),下降率约38.66%;表面粗糙度小于0.4μm时表面硬化可提高试件疲劳寿命,表面粗糙度超过0.4μm时表面硬化对疲劳性能的影响不显著;形貌测试结果表明,随着表面粗糙度的提高,磨削表面耕犁产生的沟壑数量和深度均增大,疲劳载荷作用下磨削表面裂纹源数量增加、应力集中加剧,从而导致疲劳寿命降低。较小的表面粗糙度与较大的表面硬化率均可提高DD5缓进磨削疲劳性能。

In order to study the influence laws and mechanism of surface roughness and hardening rate on fatigue property of DD5 nickel-based single crystal superalloy during creep feed grinding,the experiments were designed and tested.The results show that the increase of surface roughness leads to the aggravation of stress concentration and decrease of fatigue property.Under different grinding processes,when the value of surface roughness increases from 0.347μm to 0.687μm,the fatigue life decreases from 5.51×10^(5) to 3.38×10^(5),and the reduction rate is about 38.66%.When the value of surface roughness is less than 0.4μm,the surface hardening may improve the fatigue life of the specimen.When the value of surface roughness is more than 0.4μm,the surface hardening has no significant effect on the fatigue property.The morphological tests show that with the increase of surface roughness,the number and depth of gullies generated by ploughing on the grinding surface increase,the number of crack sources on the grinding surface increases and the stress concentration intensifies under fatigue load,which leads to the decrease of fatigue life.Lower surface roughness and larger surface hardening rate may improve the creep feed grinding fatigue property of DD5.