作　　者： (孙伶俐）; (何声馨）; (李延民）; (张二亮）;

机构地区： 郑州大学机械工程学院,郑州450001

出　　处： 《表面技术》 2017年第9期240-244,共5页

摘　　要： 目的研究WaspaloyTM镍基高温合金在裂纹萌生阶段的表面形貌特征,找出最优表面形貌参数用以表征此阶段的滑移带特征。方法对WaspaloyTM镍基高温合金试样先机械抛光,然后采用标准金相技术分别进行电解抛光和化学蚀刻,得到两种不同的表面状态。对试样进行低周疲劳试验获得疲劳寿命,并采用透射电子显微镜(TEM)和三维表面轮廓仪,观测分析WaspaloyTM镍基高温合金在电解抛光和化学蚀刻处理后的表面形貌以及裂纹萌生阶段的表面形貌和滑移带特征。对测得的表面形貌参数进行方差分析和自助抽样统计计算,找出最优参数。结果试样在经过电解抛光和化学蚀刻后,三维表面形貌S_a(表面算数平均偏差)分别是0.72 nm和13.3 nm,试样疲劳寿命分别为800和700。两种制备状态下的样品,算术平均高度增量(ΔS_a=S_a(N)-S_a(N0))的差异非常小,且ΔS_a随疲劳加载周期(N)的增加而增加,当N>100后,ΔS_a随N增加的速率减小。结论电解抛光后的表面质量更好,且表面质量越好,疲劳寿命越高。ΔS_a与表面制备方法无关,ΔS_a越大,表面越粗糙。经方差分析和自助抽样法计算分析,表面最大峰值(Sp)是最优表面形貌参数,该参数可用于区分滑移带内的损伤晶粒和未损伤晶粒。 To investigate surface roughness resulting from damage initiation of a Ni-base superalloy, and find out a most re- levant roughness parameter that can extract the salient features of slip bands. The specimens of WaspaloyTM nickel based supe- ralloy are mechanically polished, then chemically-etched and electro-polished respectively using standard metallographic tech- niques to obtain two different surface states. The fatigue life is obtained by performing low-cycle fatigue tests. The surface morphology and topographical features of fatigue-induced slip bands are investigated by the transmission electron microscope （TEM） and 3D surface profiler.The most relevant roughness parameter for describing the fatigue-induced surface damage is searched using the variance analysis integrated with the bootstrap method. The surface roughness Sa （ Surface arithmetic mean deviation） of electrolytic polishing and chemical etching the is 0.72 nm and 13.3 nm respectively, and the fatigue life of the sample is 800 and 700 after chemical etching and electrochemical polishing. The difference of the increment of the arithmetic mean height （△Sa=Sa（N）-Sa（No）） is very small for both surface states, and △Sa is exhibited to be monotonically increasing with the number of cycles （N）, the rate at which △Sa is increased is found to decrease gradually especially when N〉100. The elec- tro-polished surface is found to be smoother compared to the chemically-etched one,which offers a slightly greater fatigue crack initiation life. △Sa does not depend on the surface preparation method and the surface roughness is increasing with ASa. Based on a variance analysis integrated with the bootstrap method, the maximum peak height （Sp） is shown to be the most relevant para- meter enabling the discrimination of damaged and undamaged grains in slip bands.

关 键 词： 表面形貌 滑移带 塑性变形 裂纹萌生 镍基高温合金