X射线衍射分析高能喷丸后45钢的表层晶粒尺寸

首先对45钢试样表层进行了高能喷丸处理,然后采用X射线衍射仪(XRD)对喷丸后试样表层的组织结构进行了分析,给出了实测XRD谱和降噪后的XRD谱,通过半高宽分析了试样表层晶粒的大小,并计算了平均晶粒尺寸。结果表明:高能喷丸处理30 min后,45钢表层平均晶粒尺寸为64.847 8 nm,达到了纳米量级,说明采用高能喷丸方法可在45钢表层形成纳米层。     

电火花表面强化与喷丸复合处理对Ti811合金高温微动疲劳性能的影响

研究了Ti811钛合金表面电火花强化层的界面成分分布、耐磨和微动疲劳性能.研究结果表明:以0Cr18Ni9合金为电极材料在Ti811钛合金表面进行电火花处理可以形成合金层,显著提高了钛合金表面硬度和耐磨性能.但由于合金层硬度高,韧性较低,在微动疲劳(FF)过程中易萌生裂纹并快速扩展进入基体,致使高温下钛合金FF抗力降低.对电火花强化层进行喷丸强化(SP)后处理能够使钛合金FF抗力恢复到裸件的水平.     

Thermal Stability of Surface Layer Microstructures of Commercially Pure Titanium Treated by High Energy Shot Peening

Commercially pure titanium was treated by high energy shot peening, and annealed at a series of temperatures. The surface layers are characterized by means of scan electronic microscope, X-Ray diffraction, transmission electronic microscope and micro-hardness testing machine. The results showed that microhardness of surface layers decreases with anneal temperature, the tendency of microhardness is similar to unannealed one, in other words, the more close to the surface, the more rapidly the hardness decreases, after reaches the depth of 50 μm, the decrease becomes steadily. But the sub-surface microhardness decreased suddenly over 500 ℃, From 550 ℃ to 650 ℃, the microhardness of surface layers almost unchanged.Observing by TEM and SEM, the grain sizes of pure titanium surface layers have increased below 500 ℃; Deformation twins begin disappearing obviously at 550 ℃; The nano-scaled grains within about 10 micrometers from surface existed even at 550℃.Surface nanocrystallization is well known as one of important methods to improve surface properties. The thermal stability of nanocrystalline microstructures was related to their preparation and application. The commercial pure Ti thermal stability of nanocrystalline and deformed microstructures induced by high-energy-shot-peening (HESP) technique was investigated. The nanostructured surface and deformed sub-surface layers of specimens were prepared through HESP treatment. The thermal stability was characterized through XRD analyses of surface layers, SEM and TEM microstructure observation and microhardness measurement of specimens annealed in different temperature in the air after HESP treatments. The results showed that after HESP treatment, the microhardness of surface layers increased with treatment time, especially in the rang of about 40 micrometers from the surface, the microhardness increase was obvious. The surface microhardness decreased gradually with annealing temperature, but the sub-surface microhardness decreased suddenly over 500℃. From 550 to 650 ℃, the microhardness of surface layers almost unchanged, and is still higher than that of the undeformed microstructure. SEM observation showed that at and below 500 ℃, the microstructure changes were not obvious. At 550 ℃, the grains in surface layers grew remarkably both in SEM and TEM images at 20 micrometers deep, and the deformed twins formed in HESP treatment could be seen in the subsurface. In addition, the TEM images showed that even at 550 ℃, the nanosized grains existed within 10 micrometers from surface.     

Surface Modification of 304 Steel Using Triple-Step Shot Peening

This paper reports the influences of triple-step shot peening (SP) on the microstructure and residual stress evolution for the 304 stainless steel. The microstructure and residual stress were characterized by X-ray diffraction analysis methodology. After triple-step SP, the domain sizes decreased while the dislocation density and compressive residual stress increased as a result of the austenite and martensite in the peening deformed layer. With an increase in depth, the micro-strain for austenite decreased gradually while the micro-strain for martensite increased first, and then decreased.     

Fretting Fatigue Improvement of Ti6Al4V by Coating and Shot Peening

Ion beam enhanced deposition (IBED) was employed to increase the fretting fatigue resistance of Ti6AI4V. CrN and TiN hard coatings were applied on the base material and shot peening was combined with the hard coatings to study the duplex effect on fretting fatigue resistance. The IBED coatings exhibited a good bonding strength. They did not spall off even after shot peening. However, an optimum composition of CrN showed better fretting fatigue resistance than that of TiN with the same processing parameters.     

7A65铝合金喷丸强化表面完整性及疲劳性能

目的 以7A65高强度铝合金为研究对象,研究喷丸强度、弹丸介质(铸钢丸和陶瓷丸)对靶材疲劳性能的影响规律。方法 利用扫描电镜、激光共聚焦显微镜、X射线衍射仪等仪器表征喷丸强化7A65铝合金表面完整性和疲劳失效断口,分析喷丸工艺参数与疲劳性能、断裂模式的相关性。结果 喷丸强化后铝合金表面粗糙化严重,表面粗糙度从初始0.622 μm增加至4.736 μm(铸钢丸、喷丸强度为0.22 mmA),并出现褶皱损伤;在相同喷丸强度下陶瓷丸喷丸表面粗糙度较低,无褶皱损伤。2种弹丸在金属表面引入的残余应力场基本相同,残余压应力层深约300 μm,最大残余压应力值为-480.6 MPa,其产生位置为距离表面75 μm处(喷丸强度为0.22 mmA)。铝合金疲劳性能对铸钢丸介质敏感性较高,当喷丸强度较低(0.11 mmA)时喷丸强化效果最佳,疲劳寿命是原始寿命的5倍多,疲劳源从表面转移至次表面(500 μm);当喷丸强度增至0.22 mmA时,裂纹源向表面靠近,疲劳寿命为原始寿命的2倍。铝合金疲劳性能对陶瓷丸介质敏感性较低,在喷丸强度为0.11～0.22 mmA时疲劳寿命较为稳定,在喷丸强度为0.11 m...     

Internal Friction and Elastic Study on Surface Nanocrystallized 304 Stainless Steel Induced by High—energy Shot Peening

The 304 stainless steel with nanostructured surface layer was successfully obtained by using the high-energy shot peening(HESP) method.The internal friction and Young‘s modulus of this kind of surface nanocrystallized material were dynamically measured by means of the vibrating reed apparatus.The results implied that different treatment time could induce different microstructure and distribution characteristic of defects in this kind of materials.It is also demonstrated that there is a transition layer between the nano-layern on surface and the coarse grain region inside.The transition layer obviously has certain influence on the overall mechanical properties.     

Micromechanical Characteristics of the Surface Layer of 45 Steel After Electric-Spark Treatment

Materials Science - We analyze the principal micromechanical characteristics of the surface layers of 45 steel with electricspark coatings, namely, their microhardness, microplasticity (creep),...     

高能喷丸处理对7A52铝合金表面微观组织结构及性能的影响

随着金属表面自纳米化技术的不断发展,金属材料的表面性能得到了明显提升。通过SEM、EBSD、TEM和HRTEM等分析测试手段,对高能喷丸处理后的7A52铝合金表面纳米化机理进行了分析。结果表明,随喷丸时间的延长铝合金表面硬度显著增大,当喷丸时间为50min时,表面硬度约为270HV,与基体相比提高了近1.5倍。此时铝合金外表面均匀分布着平均晶粒尺寸约为14.16nm的等轴晶,距表面约60μm处分布着以小角度晶界为主的微米级亚晶。7A52铝合金表面纳米级晶粒的形成机理主要是:晶粒变形使晶内逐渐形成高浓度位错,位错的缠绕、塞积对基体晶粒进行了初步分割细化,在往复载荷的作用下最终在表面形成了等轴的随机取向分布的纳米级晶粒。     

Comparison of Surface Treatment Methods for Promoting the Adhesion of Glass on Titanium

A glass allowing the wetting of titanium has previously been developed. Two surface treatments promoting glass adhesion on titanium are compared: preoxidation and phosphatation combined with preoxidation. After preoxidation at 700 °C, a 1 m-thick TiO2 layer covers titanium. The phosphated titanium substrates are oxidized at 600 °C to obtain a 20 m-thick oxifluoride layer. After firing, glass adhesion is obtained with both surface treatments, but a critical time of firing appears with preoxidized titanium. WDS analysis suggests that diffusion of TiO2 into the glass is responsible for adhesion on preoxidized titanium, while a complex oxifluoride layer allows redox phenomena in the case of phosphated titanium. Pull-off tests have measured a maximum strength from 1.5 to 3 MPa whatever the surface treatment. Measurement of transverse crack densities in the vitreous coatings gives a higher value for phosphated than for preoxidized titanium. This confirms that better adhesion is obtained after phosphatation treatment.     

42CrMo曲轴钢喷丸强化有限元模拟

喷丸强化能够有效提高42CrMo曲轴钢的抗疲劳性能,且喷丸数值模拟是制定喷丸工艺方案、评估喷丸后工件表面疲劳抗力的主要理论工具。为了体现喷丸过程中的随机性,利用MATLAB软件提供的Rand随机函数产生弹丸的位置,建立随机喷丸模型,并在此模型基础上研究弹丸直径、弹丸材料、冲击速度以及覆盖率与残余应力间的分布规律,进一步讨论喷丸工艺对42CrMo曲轴钢表面粗糙度的影响。研究发现:随着弹丸直径以及速度的增大,残余应力增大,抗疲劳性能提高,但粗糙度也相应增大;随着覆盖率的增大,残余应力增大,表面残余应力分布更加均匀,稳定性提高;同时弹丸强度越高,残余应力越大。通过喷丸试验对随机多弹丸模型进行验证,为喷丸工艺的精确控制提供了科学依据和理论基础。     

喷丸强化对2XXX铝合金疲劳寿命的影响

研究喷丸对2XXX铝合金拉-拉疲劳性能的影响。对未喷丸试样和喷丸强化试样的微观组织、显微硬度、残余应力和拉-拉疲劳性能进行对比分析。结果表明:喷丸处理后,试样的组织和微结构未发现明显变化,但其粗糙度、残余压应力和显微硬度有所提高,分别是未喷丸试样的6.25倍,3.85倍和1.12倍;拉-拉疲劳性能显著提高,其中值疲劳寿命是未喷丸的1.67倍。在99.9%存活率下,喷丸试样的安全寿命是未喷丸试样的1.45倍。且表面喷丸强化后疲劳裂纹源由多个变为一个。     

Evaluation of the State of Subsurface Layers of the Metal Subjected to Shot Peening with the Help of Surface Acoustic Waves

Materials Science - We study the surface layers of the metal of low-carbon steel after shot peening. The velocity of surface Rayleigh waves is determined by the pulse-phase method at frequencies of...     

GH909合金喷丸强化残余应力场的研究

研究了GH909合金不同喷丸强化工艺下的残余应力场和残余应力在550℃的松驰情况，总结了喷丸强化所获得的残余应力场特性。结果表明，GH909合金经适当喷丸强化后获得的有益残余压应力场可改善其疲劳性能。     

喷丸强化对7050铝合金微观组织和耐磨性的影响

目前,有关增压喷丸对7050铝合金耐磨性能的影响研究鲜见报道。通过增压喷丸方式在7050铝合金表面制备纳米晶层;用X射线衍射仪、光学显微镜、透射电镜观察并分析了纳米晶层的组织结构,统计了晶粒尺寸大小和变形层的厚度;通过维式硬度计测量了样品喷丸前、后的显微硬度;采用钻盲孔法测试了残余应力的分布;在油润滑条件下对喷丸前、后样品进行了摩擦磨损试验,通过磨损失重和形貌对比分析了耐磨性能。结果表明:增压喷丸使7050铝合表面发生严重的塑性变形,变形层平均厚度约为140μm,表层纳米晶粒平均尺寸约为80 nm,硬度比基体提高了1.38倍,耐磨损性提高了1倍以上。试样表面经增压喷丸撞击产生的塑性变形引起的晶粒细化以及加工硬化现象的共同作用,是其显微硬度和耐磨性能提高的主要原因。     

喷丸法与化学处理法清除气门氧化皮的对比分析

以4Cr9Si2和21—4N两种材料的气门为例进行了化学处理与喷丸法去除气门热处理氧化皮的试验,通过对直线度、圆跳动、表面粗糙度及耐蚀性能的对比分析得出,化学处理技术可以有效克服喷丸技术使工件变形大、表面粗糙度大、耐蚀性能降低的缺点,提高了产品质量,更适合于生产应用。     

喷丸对TB6钛合金疲劳应力集中敏感性的影响

针对航空用TB6高强钛合金,本工作研究了应力集中条件下喷丸对其疲劳性能的影响规律.采用旋转弯曲疲劳试验机分别测试了两种应力集中系数的试棒的疲劳寿命及极限,采用扫描电镜分析了疲劳断口,采用MTS试验机测试了试棒的拉伸性能,并采用白光干涉仪测试了试样的表面形貌.结果表明:当应力集中系数由Kt=1提高至Kt=2时,TB6钛合金试棒的疲劳极限从537.5 MPa下降至335.5 MPa,表现出明显的应力集中敏感性.而经过喷丸后,Kt=1和Kt=2的试棒的疲劳极限分别提高了33.5％和22.2％,缺口敏感性下降了48％.喷丸有利于降低TB6钛合金的疲劳应力集中敏感性.