溅射Ni-5Cr-5Al纳米晶涂层抗高温氧化性能

研究了一种低Ｃｒ、低Ａｌ的Ｎｉ－Ｃｒ－Ａｌ系合金Ｎｉ－５Ｃｒ－５Ａｌ（摩尔分数,％）溅射涂层的抗高温氧化性能。结果表明,虽然Ｎｉ－５Ｃｒ－５Ａｌ溅射涂层在１０００℃氧化２０００小时后外面表生成ＮｉＯ,ＮｉＡｌ２Ｏ４、Ａｌ２Ｏ等复杂氧化物,但表现出很高的抗高温氧化性能。进一步分析表明,这一方面与溅射纳米晶涂层上生成的外氧化物粘附性好有关,另一方面与在ＮｉＯ,ＮｉＡｌ２Ｏ４和涂层之间生成一导听α－Ａｋ     

溅射Ni-8Cr-3.5Al纳米晶涂层的抗高温氧化行为

对Ｎｉ－８Ｃｒ－３．５Ａｌ质量分数,％合金及其纳米晶涂层进行了１０００℃空气中高温氧化研究。结果表明：Ｎｉ－８Ｃｒ－３．５Ａｌ纳米晶涂层的抗高温氧化性能优于Ｎｉ－８Ｃｒ－３．５Ａｌ合金。这主要在于Ｎｉ－８Ｃｒ－３．５Ａｌ纳变涂层表面生成了具有分层结构含一连续α－Ａｌ２Ｏ３内层的氧化膜,而Ｎｉ－８Ｃｒ－３．５Ａｌ合金则生成了由Ｃｒ２Ｏ３内氧化物组成的氧化膜。讨论了涂层氧化膜的生成过程。     

溅射Ni-5Cr-5Al纳米晶涂层高温氧化

研究了一种低Ｃｒ,低Ａｌ的溅射Ｎｉ－５Ｃｒ－５Ａｌ（原子百分数）纳米晶涂层在９００℃的高温氧化行为,观察并分析了不同氧化时间涂层表面氧化物的生成情况。发现由于Ａｌ,Ｃｒ含量较低,不能生成一层完整的Ａｌ２Ｏ３或Ｃｒ２Ｏ３保护膜,而是生成一种由ＮｉＯ,ＮｉＡｌ２Ｏ３４尖晶石相和Ａｌ２Ｏ３组成的复杂氧化物。     

微晶化对Ni-5Cr-5A1合金氧化产物的影响

利用磁控溅射在Ｍ－５Ｃｒ－５Ａ１（原子分数,％）合金上制备与基体相同成分的微晶涂层．获得的涂层在 １０００℃空气中进行了氧化实验．结果表明, ２００ ｈ氧化后涂层表面生成了分层结构的氧化膜：外层为ＮｉＯ和ＮｉＡ１２Ｏ４,内层为连续致密的α－Ａ１２Ｏ３．微晶化使得Ｎｉ－Ｃｒ－Ａ１系三元合金表面生成一层连续Ａ１２Ｏ３所需的Ｃｒ、Ａ１含量大大降低．     

K52合金纳米晶涂层的1 000℃氧化行为

对K52合金及其溅射纳米晶涂层在常压空气中进行了1 000℃抗氧化试验,用x射线衍射(ⅪRD)、扫描电镜能谱仪(SEM/EDX)、透射电镜(TEM)和电子探针(EPMA)等方法,对涂层形貌、组织和组成相以及氧化物的成分等进行了测定.研究结果表明:K52纳米晶涂层的抗高温氧化性能优于其基体合金.这主要由于纳米晶涂层表面生成了均一、致密的的a-AlzO3膜,而铸态合金则生成了疏松的Cr2O3和TiO2的混合氧化膜.讨论了氧化膜的形成机理.     

溅射纳米晶IN738合金涂层的抗循环氧化行为

研究了高温合金IN738及其溅射纳米晶涂层的抗循环氧化行为,结果表明：纳米晶涂层在950℃的抗循环氧化性能比铸态合金好,纳米晶涂层氧化时形成双层的外氧化膜,其内层为连续的Al2O3氧化层,具有了的保护性和粘附性,提高了合金抗循环氧化性能。     

溅射纳米晶IN738合金的恒温氧化行为

利用磁控溅射方法在IN378合金上制备了同成分的纳米晶涂层,研究了该合金与纳米晶涂层在800℃、900℃和1000℃ 的怛温氧化行为。结果表明：纳米晶涂层在900℃和1000℃氧化时能形成双层的外氧化膜,表层为TiO2和Cr2O3为主的混合氧化物层,内层为连续的AI2O3层,没有内氧化及氮化,但在800℃氧化却不能形成连续的AI2O3内层。讨论了纳米晶的氧化机理。     

合金元素钕对5621S钛合金氧化膜粘附性的影响及其作用机制

采用声发射技术研究了5621S及添加1％Nd的5621S钛合金,在700℃、800℃、850℃空气中所形成的氧化膜于冷却过程中的开裂和剥落。重点分析了含Nd合金所形成的复合氧化物“钉子”对氧化膜的粘附性的影响,“钉子”的存在对于膜内裂纹的扩展起着延长距离及阻碍作用。实验表明,含钕合金氧化膜的粘附性虽得到极大改善,而膜仍易于开裂。这是因为在冷却过程中,“钉子”受到大的压应力。如果“钉子”较大,就会成为萌生裂纹的起始点。文中还分析了裂纹产生机制。     

微晶化对Ni-5Cr-5Al合金氧化产物的影响

利用磁控溅射在Ｎｉ－５Ｃｒ－５Ａｌ（原子数,％）合金上制备与基体相同成分的微晶涂层,获得的涂层在１０００℃空气进行了氧化实验。结果表明,２００ｈ氧化后涂一成了分层结构的氧化膜：外层为ＮｉＯ和ＮｉＡ１２Ｏ４,内层为连续致密的α－Ａ１２Ｏ３。微晶化使得Ｎｉ－Ｃｒ－Ａｌ系三元合金表面生成一层连续Ａ１２Ｏ３所需的Ｃｒ、ＡＬ含量大大降低。     

溅射纳米晶Ni20Cr涂层的高温氧化行为

利用溅射法在Ni20Cr合金表面制备相同成分的纳米晶涂层,研究了该合金与纳米晶涂层在空气中1000℃的恒温氧化和抗循环氧化行为.结果表明,纳米晶涂层恒温氧化时生成单层连续氧化膜,氧化产物以Cr2O3为主,有少量的NiCr2O4存在.经1000℃循环氧化,纳米晶涂层生成的氧化物致密且颗粒细小,氧化膜相对较完整.溅射纳米晶...     

Effect of Nanocrystallization on Sulfur Segregation in Fe–Cr–Al Alloy during Oxidation at 1000°C

From the 1980’s a theory named “the sulfur effect” has been applied to explain the scale adhesion and the reactive-element effect (REE) during high-temperature oxidation. It claims that the bond between the oxide scale and the metal substrate is intrinsically strong and that impurity sulfur in the metal segregates at the oxide scale/substrate interface and weakens the bond, and that REs getter the sulfur impurity and prevent it from segregating to the interface. In the present study, a cast polycrystalline sulfur-containing Fe–25Cr–5Al-1S (wt.%) alloy and its magnetron-sputtered nanocrystalline coating were oxidized at 1000°C, and the specimens were examined by XRD and SEM. The scale formed on the cast alloy was cracked and detached from the substrate even after isothermal exposure, and obvious sulfur enrichment was detectable at the scale/substrate interface. While, the scale formed on the nanocrystalline coating was very adherent after 100 cycles oxidation. Here, sulfur was preferentially distributed in the outer scale and internal oxides rather than at the scale/substrate interface. These results provide evidence that nanocrystallization can prevent sulfur segregation at the scale/substrate interface, hence enhance scale adhesion.     

Investigation of Adhesion and Fracture Toughness of Thermally Grown Oxide Scales by Interface Indentation Test

HIGH TEMPERATURE ALLOYS rely on theformation of a dense layer against oxidation.Howeverthe crack,spallation and detachment of oxide layeunder growth stress and thermal stress fromtemperature difference cause the failure of theprotective layer.Therefore,high temperature materialsare required forming a good oxide scale with highstrength and high interface bonding strength.Anappropriate measuring method and evaluation fooxide/metal interfacial adhesion is of great importanceto understand …     

Effect of Multiple Laser Shock Processing on Microstructure and Mechanical Properties of Ti-5Al-4Mo-4Cr- 2Sn-2Zr Titanium Alloy

对Ti-5Al-4Mo-4Cr-2Sn-2Zr钛合金进行了不同能量和冲击次数的激光冲击强化,通过残余应力、显微硬度、XRD和TEM分析其对力学性能和微观组织的影响。结果表明,功率密度和冲击次数对残余应力和显微硬度都有较大影响,激光冲击强化后,显微硬度和残余应力都有大幅度提升,并形成一定厚度的变形层,增加冲击次数或者增大功率密度都可提高其幅值和影响深度。不同冲击参数下的XRD测试表明,激光冲击强化后衍射峰位置没有发生变化,但有展宽。激光3次冲击后可在表面形成一层纳米晶,晶粒大小为30~60 nm,且取向随机。位错运动是Ti-5Al-4Mo-4Cr-2Sn-2Zr钛合金晶粒细化的主要原因。     

In-situ Impedence Spectroscopy Study of Electrical Conductivity and Ionic Transport in Thermally Grown Oxide Scales on a Commercial FeCrAl Alloy

In-situ impedance-spectroscopy measurements were performed at temperatures between 600 and 1,000 °C to investigate ionic transport in oxide scales formed on Kanthal AF alloy. The samples were pre-oxidized at 800, 900 and 1,000 °C in air. The impedance spectra of the oxide formed at 1,000 °C exhibited essentially one semicircle, whereas samples oxidized at lower temperatures showed an additional semicircle at high frequencies suggesting a more heterogeneous oxide. The ionic-transference number, derived by measuring the voltage across the oxide scale, indicates that the oxide is a predominant electronic conductor. Ionic diffusivity in the oxide scales formed at different pre-oxidizing temperatures was calculated, using the ionic-transference number. The ionic diffusivities obtained in this way are in reasonable agreement with literature data acquired by other methods. The oxide-formation temperature has a significant influence on the conductivity and ionic-transport properties of the oxide scale.     

The Effect of Colored Titanium Oxides on the Color Change on the Surface of Ti-5Al-5Mo-5V-1Cr-1Fe Alloy

In the present investigation, a color change on the surface of Ti-5Al-5Mo-5V-1Cr-1Fe alloy was studied through thermal oxidation experiments in the temperature range of 100-1000 °C with an interval of 50 °C. The phase composition and morphology of oxide layer were characterized by x-ray diffraction and light optical microscopy, respectively. The result shows that the achieved colors after thermal oxidation followed a chromatic scale which went from silver white to light yellow to golden yellow to blue and then to light green and brownish black. The color change on the alloy mainly resulted from the different colored titanium oxides in the oxide layer. The silver white, yellow, and blue on the alloy with the oxidation temperature below 600 °C were the results of TiO₂ white tint, TiO golden tint, and Ti₂O₃ blue color, respectively. The light green was the mixed color of TiO golden tint and Ti₂O₃ blue color in the oxidation temperature range of 600-700 °C. However, at the oxidation temperatures exceeding 750 °C, the color turned to be brownish black. It might be associated with the thick, porous, and multilayered oxide layer. Consequently, it can be suggested that the illustration of the color change is vitally necessary for assessing the quality of the final workpieces according to the color change on titanium alloys.     

Effect of Lanthanum on Oxidation Behavior of Ni-20Cr- 18W-1Mo Alloys at 1373 K for 100 h in Air

对有无La元素的Ni-20Cr-18W-1Mo基高温合金进行了1373 K/100 h的等温氧化试验,分别采用扫描电镜(SEM),X射线能谱(EDX)和X射线衍射(XRD)分析了氧化试样的氧化膜表面和截面形貌特征。结果表明,La元素的添加能够极大地提高基体和氧化膜之间的结合力,使得Ni-20Cr-18W-1Mo基高温合金在1373 K时的抗氧化性提高,相比于未添加La元素的Ni-20Cr-18W-1Mo基高温合金,添加La元素的高温合金具有更小的抛物线氧化速率常数κ"和较弱的氧化膜剥落,同时,形成的表面氧化膜更加致密纤细。     

热机械“训练”工艺对Fe-20Mn-5Si-8Cr-5Ni-0．05N合金组织及形状记忆效应的影响

利用透射电镜、扫描电镜等设备研究了Fe-20Mn-5Si-8Cr-5Ni-0．05N合金在不同“训练”工艺下的组织,得到结论如下:“训练”2次时,试验合金的形状记忆效应最佳,此时可恢复的ε马氏体含量最大,并呈单一切变模式生长:“训练”3次时试验合金的母相中产生位错缠结,抑制了ε马氏体的逆转变,合金的形状记忆效应开始下降。     

固溶时效对Ti-6Cr-5V-5Mo-4Al-1Nb合金组织和力学性能的影响

研究了固溶温度、时效温度、时效时间对Ti-6Cr-5V-5Mo-4Al-1Nb(Ti-65541)合金显微组织与力学性能的影响。结果表明,在β相变点以上固溶并时效后,合金中析出细小的次生α相,初生α相完全消失;在较低温度固溶并时效后,次生α相和初生α相同时存在。时效温度对合金强度和塑性的影响最为显著,固溶温度次之,时效时间的影响最弱。随着时效温度的升高,合金的抗拉强度和屈服强度降低,塑性提高。随着固溶温度的提高,合金的强度提高,塑性降低。随着时效时间的延长,合金强度和塑性总体呈降低趋势。在740～760℃范围内固溶处理,在540～580℃范围内时效且时效时间在4～6 h内,可获得综合性能优异的Ti-65541合金。     

Effect of nanocrystallization on hot corrosion resistance of Ti-48Al-8Cr-2Ag alloy in molten salts

1 Introduction There was considerable interest in the use of γ-TiAl alloys within advanced gas turbines where they offered greater high temperature capability over conventional titanium at reduced mass. These factors would enable engines with greater th…     

La和Er对Al-13Si-5Cu-2Ni-1Mg合金组织和性能的影响

研究了La和Er对铸造Al-13Si-5Cu-2Ni-1Mg合金组织和力学性能的影响。结果表明,La对共晶Si有较强的变质作用,在合金中生成块状、长针状富La相;Er可以明显减小二次枝晶间距,在合金中可生成块状、短棒状富Er相。合金中复合添加0.2%的La和0.2%的Er时,二次枝晶间距、初生Si、共晶Si和金属间化合物的尺寸同时减小,La、Er相互作用可以抑制富稀土相的生长,使合金中引入尺寸细小且弥散分布的富稀土相,此时合金力学性能最佳,25和350℃时抗拉强度分别为274MPa和91MPa。