稀土Y离子注入对形成不同类型氧化膜合金的高温抗氧化性能的影响

：研究了稀土Ｙ离子注入对ＦｅＣｒ,ＦｅＣｒＡｌ及ＮｉＣｒ合金高温抗氧化性能的影响。结果表明,对于主要形成Ｃｒ２Ｏ３膜的ＦｅＣｒ和ＮｉＣｒ合金,通过离子注入Ｙ可以明显提高其高温抗氧化性能,但对形成Ａｌ２Ｏ３膜的ＦｅＣｒＡｌ合金,离子注入对合金抗氧化性能没有影响,添加稀土Ｙ则使ＦｅＣｒＡｌ合金抗氧化性能大大提高。分析了氧化前、后氧化膜结构变化,认为早期形成的Ｙ２Ｏ３膜对高温氧化时金属离子的扩散有不同的影响     

稀土Y对Ni-Fe-Co-Cu合金微观组织和高温氧化性能的影响

研究了稀土Y对45Ni-40Fe-8Co-7Cu合金微观组织和850℃高温氧化性能的影响。结果表明,45Ni-40Fe-8Co-7Cu合金在850℃,0.101 MPa氧分压下氧化形成以Fe_2O_3和(Ni/Co)Fe_2O_4为主的混合氧化物膜层,合金氧化遵循抛物线规律,抛物线速率常数为1.83×10~(-10)g~2·cm~(-4)·s~(-1)。添加稀土Y后,合金沿晶界析出稀土相,Y含量越高,晶界稀土相越多。添加稀土后的合金在850℃高温氧化过程中,氧化仍遵循抛物线规律,同时,晶界稀土相促进了Ni的外扩散,氧化形成的膜层以(NiCo)Fe_2O_4尖晶石氧化物为主。添加0.3%(质量分数)稀土Y的45Ni-40Fe-8Co-7Cu-0.3 Y合金850℃高温氧化形成的尖晶石结构的氧化物结晶颗粒细小,膜层致密完整,且合金抛物线氧化速率常数减小为1.15×10~(-10)g~2·cm~(-4)·s~(-1),说明添加少量(0.3%)稀土Y后,细化了氧化物结晶颗粒,提高了合金抗氧化性能。随着稀土Y添加量的进一步增加,合金高温氧化过程中,晶界稀土相不但促进了Ni的外扩散,同时加速了O的内扩散,合金抗氧化性能变差。     

含Laves相TiCr2钛铬合金的高温氧化特性

研究了含铬18%～35%(质量分数)及Laves相TiCr2钛铬合金在650,700和780℃温度下的抗氧化性能.试验结果表明,含铬量对过共析钛铬合金的抗氧化性能有显著影响.在相同条件下,含铬量低于21%的合金的抗氧化性能不如纯钛,而含铬量达到26%以上时,抗氧化性能比纯钛高2～3倍.含TiCr2钛铬合金在高温下既发生了外氧化又发生了内氧化.外氧化层没有抗氧化保护作用.铬合金化提高含TiCr2钛铬合金的抗氧化性能主要是由于形成了连续、致密的含铬内氧化层.钛铬合金的高温抗氧化性能对氧化温度敏感,氧化温度提高,则抗氧化性能明显降低.     

铝对HP40合金高温抗氧化性能的影响

 采用增重法研究了w(Al)=5%~10%的HP40合金在1 200 ℃×30 h空气中的抗氧化性能。结果表明,铝可显著提高合金的高温抗氧化性能,而且合金的高温抗氧化性能随铝含量增加而提高。1 200 ℃时,合金氧化增重与氧化时间的关系呈抛物线规律,氧化速率随氧化时间延长而逐渐下降。加入铝,改变了合金氧化膜层的物相组成和致密度,含铝合金的氧化层中含有Al2O3,而且Al2O3量随铝加入量增加而增多。     

钯能提高钨合金的抗氧化性能

<正> 美国专家通过试验证实,在钨合金(如钨钼合金或钨铬合金)中加入1％左右的钯,能提高钨合金的抗氧化性能。试验表明,在高温(1000～1250℃)氧化条件下,添加了钯的钨合金的抗氧化性能随着温度的上升有增强。     

稀土金属冶炼用新型钨钼材料的研制

本文从稀土金属冶炼用新型钨钼材料的研制着手,研究了添加几种微量稀土氧化物对钨钼材料高温、无保护性气氛下的抗氧化性。研究发现,微量稀土氧化物的添加,减慢了钨钼材料的氧化速度,较大地提高了钨钼材料的抗氧化能力。由于钨钼材料性能的改善,可使稀土冶金、玻璃、纤维等行业用的钨钼材料寿命延长、成本降低。研究表明,使用添加氧化铈、氧化钇、氧化镧的新型钨钼材料,可减少被提炼金属中的钨钼含量,使质量提高,品种上档次,满足日益发展的国内外稀土市场的要求。     

添加剂对特粗晶和超粗晶硬质合金抗高温氧化性能的影响

通过质量增加率的计算、扫描电镜观察和X射线衍射分析等,研究WC-8.4Co、WC-8.4Co-0.4Cr3C2、WC-8.4Co-0.4VC、WC-8.4Co-0.4TaC、WC-8.4Co-0.7Cr3C2、WC-8.4Co-0.7Mo2C、WC-8.4Co-0.4Cr3C2-0.05RE以及WC-8.4Co-0.4VC-0.05RE(RE为混合稀土)等8组超粗晶和特粗晶硬质合金在700℃连续氧化16 h的高温氧化行为。结果表明,VC、TaC和Mo2C的添加会降低合金的抗氧化性能;当添加量(质量分数,下同)达到0.7%时,Cr3C2才具有明显改善合金抗高温氧化性能的功能;而稀土的添加量仅为0.05%时即可明显改善合金抗高温氧化性能;添加剂可改变WC-Co合金表面CoWO4物相的生长行为,从而影响合金的抗高温氧化性能。     

稀土元素对FeCrAlNbTi电热合金结构和性能的影响

研究了添加适量稀土的ＦｅＣｒＡｌＮｂＴｉ电热合金的高温性能与微观结构。结果表明，稀土等元素的微合金化及变质效应使合金晶界强化，晶粒细化，从而使合金的抗氧化性和使用寿命提高５０％以上。     

TiAl基合金高温抗氧化研究进展

综述了TiAl基合金高温抗氧化研究进展,包括TiAl基合金氧化热力学/动力学、氧化膜组成和结构及其形成过程,以及提高合金高温抗氧化性的措施。研究结果表明,TiAl基合金高温氧化动力学一般遵循抛物线规律,且受到合金相组成和组织形貌的影响。氧化膜由外向内,主要呈TiO_2/Al_2O_3/Al_2O_3+TiO_2结构,氧化膜与基体界面处易形成降低合金抗氧化性的Z相(Ti_5Al_3O_2)和氮化产物(TiN,Ti_2AlN)。TiAl基合金中添加适量的Nb,Y,Si,Cr,Mo等元素,在改善力学性能的同时,可明显降低合金高温氧化增重。采用表面处理技术,包括表面离子注入、表面渗透扩散处理以及磷化处理等,可在合金表面形成保护层,显著提高TiAl基合金高温抗氧化性能,然而保护层的稳定性尚需提高。采用涂层技术,包括富Al涂层、陶瓷涂层以及新兴的复合涂层等,可有效地阻止氧向内扩散,抑制TiAl基合金在高温下的氧化行为。     

Al_xCoCrFeNi_2Ti_y高熵合金高温氧化行为的研究

利用非自耗真空电弧熔炼技术制备AlxCoCrFeNi2Tiy(x=0、0.2,y=0、0.5、1)多主元高熵合金,研究了不同含量Al和Ti元素对合金在800、900℃空气中氧化行为的影响。结果表明,所制备合金均有较好的高温抗氧化性能,在800、900℃空气中的氧化动力学曲线均基本符合抛物线规律。随着Al含量的增加,合金的高温抗氧化性能增强;当合金中有Al存在时,其高温抗氧化性能随着Ti含量的增加而减弱,但当合金中无Al存在时,合金的高温抗氧化性能随着Ti含量的增加先增强后减弱。Al0.2CoCrFeNi2合金的高温抗氧化性能最佳,Al0.2CoCrFeNi2Ti0.5次之。     

稀土和铬对铁基自熔合金涂层耐蚀性的影响

本研究着眼于考察稀土和合金成分对铁基自熔合金涂层的耐蚀性的影响,对不同成分的合金涂层进行了三酸一盐的浸蚀试验。结果表明在硫酸和硝酸溶液中,稀土的添加对合金涂层的耐蚀性有利,但在盐酸和氯化钠溶液中,稀土的添加对合金涂层耐蚀性无益。铬含量高的铁基自熔合金涂层在硝酸溶液中有优良的耐蚀性,但在硫酸和盐酸中的耐蚀性不如铬含量低的铁基自熔合金涂层。文中分析了不同合金在试验中的不同表现的原因,进而为铁基自熔合金的进一步工业应用提供有用的信息。     

铬元素添加对热轧低碳钢高温氧化行为的影响

 为了研究铬元素和加热工艺参数(加热温度、保温时间)对热轧低碳钢表面氧化铁皮形成过程的复合作用,采用热重分析法研究了铬含量对低碳钢在1 100~1 250 ℃空气中氧化行为的影响规律,计算了氧化速率常数,并对比了不同试验条件下氧化铁皮的物相组成、显微结构以及微区元素占比。结果表明,所有氧化过程均呈现两阶段特征,即初期氧化动力学曲线呈线性规律,中后期逐渐转变成抛物线规律,而从线性到抛物线转变所需时间会随着钢中铬含量的升高而缩短;同时,铬元素添加后氧化铁皮的结构由最外侧的Fe₂O₃层、中间的Fe₃O₄层和FeO层以及靠近基体的富铬尖晶石(FeCr₂O₄)层组成,FeCr₂O₄层在氧化过程中通过阻碍铁离子和电子的外扩散,降低了氧化速率,从而显著提高低碳钢的抗高温氧化性能。     

Effect of rare earths on oxidation resistance of heat resistant steel

The application of rare earths(RE) in the Ni saving heat resistant steel was studied by metalloscopy,scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),X-ray difference(XRD).Because the diffusion of chromium was promoted by RE,a dense and adhesive Cr2O3 layer could form rapidly at the early oxidation stage,which played a effective protection role;the pinning effect of silicon dioxide was enhanced by RE in the internal oxidation layer,which had a block effect on the diffusion of metal ions and oxygen ions at later stage of oxidation and resulted in that the high temperature oxidation rate of RE heat resistant steel was decreased.     

Oxidation of Cr-Ni coatings on diamond

The kinetics of the oxidation of chromium and chromium-nickel coated diamond powders in air at 750 and 850°C was studied by means of interrupted weighing. The coatings and metallized powders were subjected to x-ray phase analysis. Decrease of the powder mass confirms that permeation of the mass with volatile oxides predominates over the increment due to the weight of the absorbed oxygen in the oxides NiO and Cr₂O₃. The weight loss is caused by the burning away of both the coating (oxidation of chromium and its carbides to CrO with formation of CO and CO₂) and the diamond. Carbon from the diamond is also removed with CO and CO₂ as a result of successive reduction of chromium oxide by carbon, which diffuses to the oxidized layers, and further reduction of the carbides by the same mechanism. The higher the oxidation temperature and the thinner the coating, the greater the contribution of these reactions is to the processes responsible for the decrease in weight of the metallized diamonds. It is also encouraged by diffusion of carbon to the scale formed and by simultaneous diffusion of oxygen to the coating. The reactions of primary oxidation of chromium contained in the nickel solid solution, reduction of nickel by carbon and chromium, and dissolution of chromium in the reduced nickel contribute significantly to the oxidation of chromium-nickel coatings.Translated from Poroshkovaya Metallurgiya, No. 7(367), pp. 62–66, July, 1993.     

Influences of Alloying Elements on Oxidation Behavior of Steels and Microstructure of Oxide Scales

In order to figure out the oxidation behavior of steels during heating,five micro-alloyed steels were subjected to continuous and isothermal oxidation using the thermo gravimetric analyzer and the Gleeble-3500thermo-mechanical simulator.The microstructure of oxide scales,especially the thickness fractions of Fe2O3,Fe3O4 and FeO layers,was analyzed using the scanning electron microscope(SEM),electron probe microanalyzer(EPMA)and electron backscattered diffraction(EBSD)techniques.The micro-alloyed steels containing alloying elements(Si,Cr,Ni and Cu)show a higher oxidation resistance compared with the low carbon steel.It is found that alloying elements accumulated at scale/substrate interface during high temperature oxidation.Alloying elements function in two ways in the oxidation of steels:one is enhancing the scale/substrate interface and consequently suppressing the blister of scales;and the other is impeding the outward diffusion of iron cations from substrate to scales,resulting in the decrease of oxidation rate.As the diffusion of iron cations is impeded,the thickness fractions of Fe2O3 and Fe3O4of micro-alloyed steels are more than those of low carbon steels.     

Fe-2.2%Si钢在不同气氛下的高温氧化行为

为了探究硅元素、加热工艺参数(气氛、温度以及时间)对Fe-2.2%Si钢表面氧化铁皮形成过程的复合作用及影响机理,利用热重分析仪(TGA)研究了Fe-2.2%Si钢在600～1 150℃干燥空气和水蒸气条件下的高温氧化行为,利用试验得到的氧化增重数据计算出了氧化速率常数和氧化激活能,并建立了氧化动力学模型。此外,还明确了在2种气氛下氧化铁皮的生长机制与结瘤机理。试验结果表明,在2种不同氧化气氛下得到的氧化增重曲线均符合抛物线规律。当氧化气氛中含有水蒸气时,试验钢的氧化速率提高,氧化激活能降低,导致了试验钢的氧化增重增加。在2种氧化气氛下,试验钢的氧化产物均由氧化铁皮和氧化铁皮与基体界面处的富硅层组成,但在水蒸气下得到的试验钢的富硅层疏松多孔,且氧化铁皮中出现大量的孔洞以及裂纹。其氧化机制主要是氧化铁皮生长过程的生长应力以及水蒸气的存在导致生成的H₂向外扩散,造成氧化铁皮出现大量孔洞和裂纹,为氧化介质的扩散提供了通道,有利于气相物质扩散,进而促进了试验钢的氧化行为。此外,由于在氧化铁皮与基体界面形成的富硅层消耗了基体中的硅元素,导致基体表层出现贫硅区,氧化介质可以通...     

Effect of thermal spray on the microstructure and adhesive strength of high-velocity oxy-fuel-sprayed Ni-Cr coatings on 9Cr-1Mo steel

Coatings of 80Ni-20Cr and 50Ni-50Cr on a 9Cr-1Mo steel substrate were produced by high-velocity oxy-fuel (HVOF) spraying to protect the steel against steam oxidation in ultrasupercritical (USC) boilers. The oxidation studies on the coated specimens showed good protection against the scale growth on the steel substrate. Both the 80Ni-20Cr and 50Ni-50Cr coatings formed a thin protective oxide film on the coating surface. The 80Ni-20Cr coating showed Fe diffusion from the substrate to the coating and nickel diffusion from the coating to the substrate during the oxidation process. In the case of 50Ni-50Cr coatings, the diffusion process was reduced, but a continuous layer of chromium carbide was observed at the coating/substrate interface during the oxidation. The adhesive/cohesive strength of these coatings was evaluated on aged specimens at 750 °C by using a simple tensile test. The results of the as-coated 80Ni-20Cr specimens showed an adhesive-strength value of 68 MPa. On extended aging, the strength of the coating increased beyond the detection limit of the resin. The nickel diffusion from the coating to the substrate and the iron diffusion from the substrate to the coating caused the increased adhesive strength. In the case of 50Ni-50Cr, the as-coated specimens showed an average adhesive strength of 76 MPa and showed a decreasing trend on the aged specimens. The formation of chromium carbide at the interface caused inferior values in the adhesive/cohesive strength of the 50Ni-50Cr coatings. The chromium carbide formed on the coating/substrate interface was identified as M₂₃C₆-type carbide.     

Effects of chromium on crack growth and oxidation in nickel aluminide

The influence of chromium additions on crack growth and oxidation have been examined in the nickel aluminide, Ni₃Al. Crack growth rates were measured in a chromium containing alloy as a function of stress intensity at temperatures between 600 and 760°C in air, together with rates of oxide film growth, and compared with previous measurements taken from Ni₃Al. The mechanisms of crack propagation and oxidation were investigated with a range of analytical techniques, including SEM, AES, XPS, SIMS, TEM and STEM. An addition of 8% chromium had a significantly beneficial effect on both crack growth resistance and oxidation resistance between 600 and 760°C. Low oxidation rates were associated with the formation of Cr₂O₃ together with Al₂O₃ at the metal/oxide interface, consistent with chromium acting initially as an oxygen getter, and promoting the formation of a protective Al₂O₃ layer, with little internal oxidation. It is proposed that chromium was also responsible for inhibiting oxygen access to and diffusion along grain boundaries at crack tips, modifying the mechanism of crack propagation from “step-wise cracking”, dominated by oxygen embrittlement (observed in the absence of chromium), to a more conventional creep crack growth process.     

Effect of Si on high temperature oxidation of 30Cr13 stainless steel

The effect of Si on the high temperature oxidation behavior of the 30Cr13 martensitic stainless steels was investigated.The underlying mechanism was further discussed by oxidation kinetics curves, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis.It was ob-served that the addition of Si can significantly reduce the mass gain per unit area and the oxidation rate of the experimental steels.With the increase of Si content, the film surface composed of the wheat-like oxides turned into the small granular oxides after oxidation for 120 h.The SiO2 film formed on the metal substrate inhibited the outward diffusion of the metal cation and the inward diffusion of the oxygen anion; thus, the high temperature oxidation resistance was enhanced.     

An Electron Microscopy Investigation of the Transient Stage Oxidation Products in an Fe-22Cr Alloy with Ce and La Additions Exposed to Dry Air at 1073 K (800 °C)

In this study, the effects of Ce (270 ppm) and La (120 ppm) mischmetal additions on the transient oxidation of an Fe-22Cr alloy were investigated. The oxidation process was imaged in situ using a confocal scanning laser microscope. The oxidation microstructures were studied by scanning electron microscopy, energy dispersive X-ray analysis, and transmission electron microscopy with the help of focused ion beam in situ lift-out specimen preparation. The Ce and La, referred to as reactive elements, were found in nonmetallic inclusion particles in the forms of oxides, sulfides, and phosphates. An affected zone formed around rare earth (RE)-containing inclusion particles at the alloy free surface during the transient oxidation. This zone consisted of an internal Cr-oxide formed beneath the particle as well as a thinner external oxide scale on the surface compared with the surroundings. The relation of this microstructure to oxidation kinetics is discussed. With time, the RE elements diffused into the scale from the RE particles on the alloy surface during the high-temperature exposure. A diffusion mechanism is presented to describe these observations.