高合金轴承钢接触表面效应与疲劳行为的研究

发布时间：2018-05-13 00:08

本文选题：轴承钢 + 滚动接触疲劳　；参考：《昆明理工大学》2017年硕士论文

【摘要】：采用双真空冶炼工艺(VAM-VAR)生产的Cr4Mo4V轴承钢,具有较好的高温硬度和杰出的滚动接触疲劳强度,被广泛应用于飞机发动机轴承。滚动轴承通常的失效类型为疲劳剥落,但是在高性能飞机发动机轴承中环向应力加剧进而造成外圈的断裂,钢中未固溶碳化物影响轴承疲劳损伤和加工性能。本文探究了Cr4Mo4V轴承钢在滚动接触疲劳过程中的性能变化,利用有限元模拟了滚动接触疲劳加载下的球棒滚动接触应力分布,通过旋转弯曲疲劳试验研究了未固溶碳化物对Cr4Mo4V轴承钢疲劳性能的影响。(1)通过球棒滚动接触疲劳(RCF)试验机,研究了 Cr4Mo4V轴承钢在4050润滑油润滑和0.18滑滚比条件下的滚动接触疲劳和磨损性能。结果表明:Cr4Mo4V钢的应力-寿命(S-N)曲线数据分散性较大,疲劳寿命随着应力增加呈下降趋势。Cr4Mo4V钢滚动接触磨损主要为磨料磨损,黏着磨损和疲劳磨损,随着应力和时间增加磨损体积增加,滚道凹槽深度达到17 μm。通过光学显微镜(OM)和扫描电子显微镜(SEM)观察试样棒剖面与滚道交界处疲劳裂纹,发现疲劳破坏类型主要有两种:起源于表面的剥落(SOF)和起源于白蚀区的剥落(WSF)。通过滚道径向切割抛光酸蚀显示Cr4Mo4V钢滚动接触疲劳影响区,随着应力和循环接触次数的增加,在次表层依次发现黑蚀区(DER)、白蚀区(WEA)和蝴蝶组织(BW)。表面碳化物的剥落坑,黏着磨损和疲劳磨损的凹坑导致了表面起裂,白蚀区和蝴蝶组织中的碳化物和夹杂导致微裂纹的产生,链状碳化物使裂纹往深处扩展。(2)在考虑试样尺寸,次表面应力影响区和碳化物尺寸下,采用两步有限元模拟方法及“全局模型-子模型”研究球棒滚动接触疲劳。在最大接触接应力4GPa下,次表面塑性变形区域为50μm到150μm。碳化物导致局部屈服。(3)在应力比R=-1,试验频率为85Hz和室温下测试了 Cr4Mo4V轴承钢的旋转弯曲疲劳性能。利用升降法测得Cr4Mo4V钢光滑圆柱形试样的安全疲劳极限为1019MPa。光滑漏斗状试样的安全疲劳极限为1153MPa。Cr4Mo4V钢S-N曲线数据呈下降趋势且分散性较大。光滑圆柱形试样断口观察表明,发现起裂类型有5种,即表面缺陷起裂,近表面碳化物起裂,近表面非金属夹杂物起裂,内部非金属夹杂物起裂和内部碳化物起裂。光滑漏斗状试样断口观察显示破坏模式为内部碳化物起裂和氢致断裂。内部起裂断口有“鱼眼”特征;内部起裂源碳化物周围形成GBF区。Cr4Mo4V轴承钢中碳化物在循环应力下作用下发生破碎,破碎的碳化物加大了裂纹扩展速率。使用关键碳化物体积密度能够定量地分析碳化物尺寸对近表面起裂的影响。通过缺陷所在位置的名义应力幅与缺陷疲劳极限强度的比值分析了夹杂物尺寸对疲劳寿命的影响。
[Abstract]:Cr4Mo4V bearing steel produced by double vacuum smelting process (VAM-VAR) has good high temperature hardness and excellent rolling contact fatigue strength, so it is widely used in aeroengine bearings. Generally, the failure type of rolling bearing is fatigue spalling, but in the high performance aircraft engine bearing, the stress in the ring direction is aggravated and the outer ring is broken. The failure of the steel can affect the fatigue damage and the processing performance of the bearing. In this paper, the behavior change of Cr4Mo4V bearing steel during rolling contact fatigue is studied. The rolling contact stress distribution of ball rod under rolling contact fatigue loading is simulated by finite element method. The effect of undissolved carbides on fatigue properties of Cr4Mo4V bearing steel was studied by rotating bending fatigue test. The rolling contact fatigue and wear properties of Cr4Mo4V bearing steel under the conditions of 4050 lubricating oil lubrication and 0.18 sliding roll ratio were studied. The results show that the stress-life curve data of the steel w Cr4Mo4V are dispersive, and the fatigue life of the steel decreases with the increase of stress. The rolling contact wear of Cr4Mo4V steel is mainly abrasive wear, adhesion wear and fatigue wear. With the increase of stress and time, the raceway groove depth increases to 17 渭 m. By means of optical microscope (OM) and scanning electron microscopy (SEM), the fatigue cracks at the interface between the rod profile and the raceway were observed. It was found that there are two main types of fatigue failure: surface spalling (SOF) and denudation (WSF) originating in the white corrosion zone. The raceway radial cutting and polishing acid etching shows the rolling contact fatigue zone of Cr4Mo4V steel. With the increase of stress and cyclic contact times, the black corrosion zone (DERA), the white etching zone (WEAA) and the butterfly tissue (BW) are found in turn in the subsurface layer. Surface carbides spalling pits, adhesion wear and fatigue wear pits lead to surface initiation, carbides and inclusions in white etching zones and butterflies lead to microcracks, chain-like carbides cause cracks to spread deep into the depths of cracks. Two step finite element simulation method and "global model-sub-model" are used to study the rolling contact fatigue of the bat in the sub-surface stress affected zone and carbide size. The plastic deformation region of the subsurface is from 50 渭 m to 150 渭 m under the maximum contact bonding force (4GPa). The rotational bending fatigue properties of Cr4Mo4V bearing steel were tested at stress ratio Rn-1, test frequency of 85Hz and room temperature. The safety fatigue limit of smooth cylindrical specimens of Cr4Mo4V steel was determined to be 1019 MPA by means of lifting method. The safety fatigue limit of smooth funnel specimen is the S-N curve data of 1153MPa.Cr4Mo4V steel. The fracture observation of smooth cylindrical specimen shows that there are five types of initiation cracks, namely, surface defect initiation, near-surface carbides initiation, near-surface non-metallic inclusions initiation, internal non-metallic inclusions initiation and internal carbides initiation. The fracture of smooth funnel specimen shows that the fracture mode is internal carbides initiation and hydrogen-induced fracture. The fracture surface of internal crack has the characteristic of "fish-hole", and the carbides in GBF zone. Cr4Mo4V bearing steel are broken under cyclic stress, and the cracked carbides increase the rate of crack propagation. The effect of carbides size on the initiation of near surface crack can be quantitatively analyzed by using the key carbides bulk density. The influence of the size of inclusions on fatigue life is analyzed by the ratio of nominal stress amplitude of defect location to fatigue ultimate strength of defects.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1

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