材料期刊网

目的 研究不同的表面状态对WaspaloyTM镍基高温合金塑性变形局部化的影响,确定最优的评价塑性应变局部化的三维表面粗糙度参数.方法 对两组WaspaloyTM高温镍基合金先进行机械抛光至0.02μm,然后分别进行电解抛光和化学蚀刻,得到不同的两种表面状态.通过制作标准试样进行疲劳试验得到疲劳寿命,并采用原子力显微镜、扫描电子显微镜和三维表面轮廓仪分析WaspaloyTM镍基高温合金在电解抛光和化学蚀刻处理前后的表面形貌以及裂纹萌生形貌.结果 试样经过电解抛光和化学蚀刻后,电解抛光表面质量更好,三维表面粗糙度Sa(表面算数平均偏差)分别是0.001、0.018μm,经过疲劳试验后的值分别为0.024、0.026μm,表面粗糙度参数Sp(表面最大峰高)均为0.131μm.电解抛光试样的疲劳寿命为800,化学蚀刻试样的疲劳寿命为700.经过化学蚀刻和电解抛光的试样疲劳裂纹均是从滑移带处开始产生,并沿滑移带扩展.结论 表面状态影响材料的疲劳寿命,表面粗糙度小的试样疲劳寿命长.三维表面粗糙度参数Sp适用于描述材料疲劳塑性应变局部化,其临界值揭示了材料裂纹萌生.

The work aims to study influence of different surface states on plastic deformation localization of WaspaloyTM Ni-base superalloy, and determine optimal three-dimensional surface roughness parameters of evaluating plastic stress localiza-tion. WaspaloyTM nickel-base superalloy was polished to 0.02μm, and then electrolytic polishing and chemical etching were carried out respectively to obtain two different surface states. Fatigue life was obtained by performing fatigue test to standard sample fabricated for this purpose, and surface morphology and crack initiation of WaspaloyTM nickel-base superalloy were in-vestigated by using atomic force microscopy, scanning electron microscopy and 3D surface profiler. Quality of the electrolytic polished surface was better. 3D surface roughness Sa (surface arithmetic mean deviation) was 0.001μm and 0.018μm respec-tively, and 0.024μm and 0.026μm respectively after the fatigue test. The surface roughness Sp (surface maximum peak height) was 0.131μm. Fatigue life of the sample subject to chemical etching and electrochemical polishing was 800 and 700 respec-tively. The fatigue cracks on the sample subject to chemical etching and electrochemical polishing started from the slip bands and extended along the slip bands. The initial surface state has affects fatigue life of the material; three dimensional surface roughness parameter Sp is the best description of material fatigue plastic deformation localization, of which critical value reveals the crack initiation of the material.