高能喷丸对GH4169合金表层组织和性能的影响

发布时间：2018-12-30 10:21

【摘要】：GH4169合金具有良好的高温力学性能、较强的热腐蚀抗力以及优异的高温抗氧化性,已广泛应用于航空航天领域。然而,GH4169合金硬度不高、抗疲劳强度一般,限制了其在航空结构件中的进一步应用。本文通过对GH4169合金进行高能喷丸处理,研究了喷丸时间和弹丸尺寸对合金表面状态、表面粗糙度、显微硬度、残余应力和表层组织的影响,对比了干喷丸和湿喷丸下合金表层组织和性能差异,探究了GH4169合金喷丸强化机理,获得了以下结论:GH4169合金干喷丸处理后表面缺陷增多,表面完整性下降。1mm和2mm弹丸喷丸后,试样表面缺陷主要表现为翘曲,起皮和塌陷。而4mm弹丸喷丸后,试样表面缺陷主要表现为长条状和多边形状缺陷。干喷丸处理后GH4169合金表面粗糙度、显微硬度和残余应力都显著提升。其中1mm弹丸喷丸3min时,表面粗糙度最小,为2.857μm;4mm弹丸喷丸10min时,表面显微硬度提升最大,为401HV,较原始试样硬度(289HV)提升了39%;随着喷丸时间延长,表层残余应力场强度增加,1mm弹丸喷丸10min时,表层最大残余应力达到了-684MPa。XRD分析结果显示,GH4169合金喷丸后试样表层无相变发生,且随着喷丸时间和弹丸尺寸增加,衍射峰的强度降低,半高宽逐渐增大,表明组织细化程度增加。此外,随着喷丸时间和弹丸尺寸增大,喷丸作用层厚度不断增加。4mm弹丸喷丸10min时,喷丸作用层厚度最大,达到450μm。与干喷丸相比,湿喷丸后试样表面缺陷明显减少,表面缺陷主要表现为起皮。且随着弹丸尺寸增大,水对弹丸的缓冲和润滑作用更显著,对材料表面完整性的保护程度也越高。湿喷丸后试样表面粗糙度较干喷丸相比显著降低,2mm弹丸喷丸10min时,表面粗糙度降低幅度最大,达到了53%。此外,与干喷丸相比,湿喷丸后试样表面残余应力更大,2mm弹丸喷丸10min时,表面残余应力提升了9%左右。GH4169合金经喷丸后,表层形成了较强的残余应力场,表层晶粒内部出现了大量的形变孪晶,且距离喷丸面越近,多系孪晶间的相互交割现象也越明显,孪晶数量越多,组织细化程度越高。因此,GH4169合金干喷丸和湿喷丸的表面强化都是由表层组织细化、形变孪晶形成以及残余应力强化等因素综合作用的结果。
[Abstract]:GH4169 alloys have been widely used in aerospace industry due to their good mechanical properties at high temperature, strong thermal corrosion resistance and excellent high temperature oxidation resistance. However, the hardness and fatigue strength of GH4169 alloy are not high, which limits its further application in aeronautical structure. The effects of shot peening time and projectile size on the surface state, surface roughness, microhardness, residual stress and surface microstructure of GH4169 alloy were studied in this paper. The microstructure and properties of the alloy under dry and wet shot peening were compared, and the mechanism of shot peening strengthening of GH4169 alloy was investigated. The following conclusions were obtained: the surface defects increased and the surface integrity decreased after shot peening of GH4169 alloy. After shot peening by 1mm and 2mm, the surface defects increased and the surface integrity decreased after shot peening with 1mm and 2mm. The surface defects of the sample mainly show warping, peeling and collapse. However, after 4mm shot peening, the surface defects of the samples were mainly strip and multilateral shape defects. The surface roughness, microhardness and residual stress of GH4169 alloy were improved after shot peening. When 1mm shot peening 3min, the surface roughness was the smallest, and when shot peening 10min was 2.857 渭 m or 4mm, the surface microhardness was the highest, which was 401 HV. the surface roughness was 39% higher than that of the original sample (289HV). With the prolongation of shot peening time, the intensity of surface residual stress field increases. When 1mm shot peening 10min, the maximum residual stress of the surface layer reaches-684MPa.XRD analysis results show that there is no phase change in the surface layer of GH4169 alloy after peening. With the increase of shot peening time and projectile size, the intensity of diffraction peak decreases and the half-maximum width increases, which indicates that the degree of microstructure refinement increases. In addition, with the increase of shot peening time and shot size, the thickness of the action layer of shot peening increases continuously. When 4mm shot peening 10min, the thickness of shot peening layer is the largest, reaching 450 渭 m. Compared with dry shot peening, the surface defects of wet shot peening samples were obviously reduced, and the surface defects were mainly peeled. With the increase of the size of the projectile, the buffering and lubricating effect of water on the projectile is more obvious, and the protection degree of the surface integrity of the material is also higher. After wet shot peening, the surface roughness of the sample was significantly lower than that of dry shot peening. When 2mm shot peening 10min, the surface roughness of the sample decreased to 53%. In addition, compared with dry shot peening, the residual stress on the surface of wet shot peening is greater than that of dry shot peening. When 2mm shot peening 10min, the surface residual stress increases by about 9%. After shot peening, a strong residual stress field is formed on the surface of GH4169 alloy. There are a large number of deformation twins in the surface grain, and the closer to the shot peening surface, the more obvious the intersecting phenomenon between the multi-system twins is, and the more the number of twins is, the higher the degree of microstructure refinement is. Therefore, the surface strengthening of GH4169 alloy by dry shot peening and wet shot peening is the result of the combined effect of surface microstructure refinement, deformation twin formation and residual stress strengthening.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG668

【参考文献】