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1.
不锈钢渗铝后的表面组织、成分及其耐熔锌腐蚀性能   总被引:1,自引:0,他引:1  
由于液态锌的腐蚀,使在热镀锌生产线上的工作零件失效严重,严重阻碍了热镀锌行业的进一步发展.对此,研究了采用固体粉末包埋法对1Cr18Ni9Ti不锈钢进行渗铝,再采用热氧化的方法使渗铝层表面原位生长Al2O3薄膜.结果表明:渗铝层表面主要由FeAl相组成,渗铝层呈多层结构,分为渗层外层(约25C μm)、过渡层(约为50 μm)和渗层内层(约为300 μm).渗铝层表面铝的浓度较高,超过30%(质量分数),渗铝层发生选择性氧化,在表面生成一层均匀致密的Al2O3膜,所得膜的厚度约为20 μm.通过大量试验得出,渗铝层具有良好的耐锌液腐蚀性能,可作为锌液与铁表面接触的良好隔离层.  相似文献   

2.
激光重熔对热浸渗铝层组织和性能的影响   总被引:2,自引:0,他引:2  
热浸渗铝层中通常存在大量的孔洞和裂纹,严重影响渗铝钢的耐蚀性.采用JHM-1GY-400型YAG(晶体)激光器对Q235钢的热浸渗铝层进行激光熔凝处理,借助扫描电镜、电子探针、金相显微镜、X射线衍射仪、显微硬度计等仪器对激光处理前后渗铝层的显微组织、相组成及性能进行了分析.通过测定在3.5%NaCl水溶液中的极化曲线,讨论了激光熔凝处理对渗铝层耐蚀性的影响.结果表明,采用适当的激光处理工艺,可消除渗铝层中的裂纹及孔洞,渗层变得更加致密,从而使其在3.5%NaCl水溶液中的耐蚀性高于未激光处理的渗层.并且其显微组织发生了高铝ξ相(FeAl2)向低铝β2相(FeAl)的转变,导致渗层显微硬度和脆性降低,渗层综合性能得到改善.  相似文献   

3.
为提高电热合金丝的抗高温氧化性能,采用固体粉末包埋法在Cr20Ni80电热合金丝表面制备渗铝涂层,通过高电阻电热合金快速寿命装置对渗铝试样在恒温1 000℃下进行高温氧化试验、在恒温1 200℃下进行快速寿命测试并拟合电阻随时间的变化曲线,利用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱分析(EDS)和热重分析仪(TGA)研究了渗铝涂层结构、氧化膜形貌、氧化膜相组成以及渗铝试样氧化动力学.结果 表明:渗铝试样快速寿命相较于未渗铝试样提高了7.62%.渗铝涂层为双层结构,内外层厚度约为5岬和40 μm.渗铝试样氧化动力学曲线基本符合抛物线规律.氧化膜分为3层:最外层为Al2 O3与微量NiO;次外层为NiAl及少量Al2O3、NiO;最内层是富Cr层和Cr2O3,并存在少量不连续分布的SiO2.氧化初期,渗铝试样迅速在表面形成了一层均匀致密的Al2O3保护性氧化膜,有效地改善了Cr20Ni80电热合金丝抗氧化性能.  相似文献   

4.
为提高Q235钢的耐蚀性和资源化利用煤矸石,采用粉末包埋法,以煤矸石为主渗剂,铝粉和镁粉为还原剂,在Q235钢表面制备出厚度达100μm的渗硅层.采用金相显微镜、显微硬度计、X射线衍射仪分析了渗硅层的组织结构及硬度;通过浸泡腐蚀试验测试了渗硅层耐酸、盐、海水、煤水腐蚀性能,并与发蓝试样进行比较.结果表明:煤矸石渗硅层中含有Fe3Si,Al2SiFe等新相生成,并且主要由含Si的α相固溶体组成,渗硅层的硬度最高达348.7 HV1N,为基体的2.6倍;渗硅层耐酸、盐、海水、煤水腐蚀性较基体分别提高了1.32,1.42,1.47,0.54倍,较发蓝试样分别提高了1.18,1.37,1.10,0.43倍.  相似文献   

5.
为了探讨施加直流电场对固体粉末渗硅渗速的影响,以20钢为基材,通过在渗硅介质与被改性样品间施加直流电场,研究快速粉末渗硅的合适工艺条件,并研究该工艺获得的渗层性能。结果表明:直流电场可降低粉末渗硅温度,显著提高渗硅速度;可使常规粉末渗硅温度从1 050℃以上降低到750℃;加热温度为800℃,直流电流6 A时,20钢的渗硅层厚约85μm;直流电场条件下获得的渗硅层主要由Fe5Si3相组成,在700℃具有良好的抗氧化性能。  相似文献   

6.
一、前言 为防止高温氧化和热腐蚀,金属材料表面渗铝是沿用已久的方法。迄今为止,工艺繁多,但广为应用的仍是“固体粉末包埋渗铝”工艺(简称包埋渗铝)。国内主要采用铝铁合金粉末包埋渗铝。但由于铝铁合金粉末在球磨制备时须反复过筛。渗铝剂在使用过程中要多次清理,从而对工作环境造成严重污染。 目前,国外采用包埋渗铝工艺时,主要用氧化铝-铝粉末渗铝剂。除了具有一般粉末包埋渗铝工艺的优点外,由于使用了廉价的工业锻烧氧化铝粉末作为渗铝剂的主要原料,为渗层质量更加稳定提供了可靠保证,同时也简化了渗铝剂的清理工作,改善了劳动条件;渗铝剂中铝粉含量可调范围大,渗铝速度比铝铁合金  相似文献   

7.
张振国  汤峰 《材料保护》2005,38(8):51-53
为了改善ST12钢板的耐腐蚀能力,采用粉末渗锌工艺对ST12钢进行了合金化处理,然后用光学显微镜观察了合金化层的组织形貌;用X射线衍射方法分析了合金化层表面的相组成;用M352 Corrosion Measurement System电位差仪测量了电位,并对其进行了静态腐蚀试验.结果表明:合金化层由Г相和δ1相组成,δ1相为主,成分为FeZn7;合金化后的静态防腐蚀性能远远超过ST12,并且优于同等条件下的热镀锌;合金化层的电位为-920 mV左右,可作为阳极性涂层对钢铁基体起保护作用.本研究改善了ST12钢的防腐蚀能力,扩大了其应用范围.  相似文献   

8.
金属表面双辉低温等离子渗铬可提高金属耐蚀性,且不损坏其组织和性能等.在650℃对40Cr钢表面进行双辉低温等离子渗铬,采用光学显微镜、扫描电镜、能谱仪、辉光放电剥层成分分析仪、X射线衍射仪及电化学腐蚀性能测试对渗铬试样的形貌、成分、元素分布、相结构和耐蚀性能等进行了研究.结果表明:40Cr表面沉积层厚4~5μm,沉积层与基体间出现少量的脱碳层,基体组织均匀、晶粒细小;渗镀试样内铬元素呈梯度分布;基材渗铬后表面铬含量提高,渗铬试样氮化后表层物相以CrN为主;与基材相比,渗铬试样在1 moL/L NaCl溶液中的抗点蚀能力增强,耐腐蚀性能提高.  相似文献   

9.
稀土元素La对传统的铝层的结构及其抗高温氧化性能的影响机理尚未充分定型.以低碳钢为基体,预置纯镍和Ni-La2O3复合电镀层,采用固体粉末法进行渗铝,对渗铝试样进行高温氧化试验.用光学显微镜(OM)、扫描电镜及能谱(SEM/EDAX)等方法对试样进行了分析,发现稀土元素La促进了渗铝的过程,使渗铝层中铝含量较高,质量分数为35%,并且渗层组织细小均匀,表面质量好;高温氧化后,Ni-La镀层渗铝层表面形成的氧化膜薄而致密,氧化增重较小,具有较好的抗高温氧化性能.  相似文献   

10.
包埋渗铝法可在钢基体表面制备出一层致密、坚固、连续的Fe-Al渗层,以改善基体性能。本文在不同温度和不同时间下对Q235低碳钢进行包埋渗铝,形成Fe-Al渗层,采用X射线衍射、扫描电镜及能谱分析等方法研究了渗铝层的物相结构、表面及截面形貌和成分,采用显微硬度仪测量了截面硬度。结果表明,不同渗铝温度下获得的渗铝层,主要含有Fe2Al5和FeAl3两相,且750℃得到的渗层存在较多Fe2Al5相;随着渗铝温度升高,Fe-Al渗层厚度增加,Al原子扩散系数增大,但显微硬度降低;不同渗铝时间下制备的渗铝层,物相仍以Fe2Al5和FeAl3为主,但随着渗铝时间延长,FeAl3含量减少,且Al原子扩散系数变大,渗层显微硬度略有降低。在进一步分析Fe-Al渗层形成的热力学与动力学基础上,总结了渗铝层形成的扩散机制。  相似文献   

11.
A process has been developed for forming dense, adherent aluminized layers on Ni-Cr-type alloys. This process development was based on a previous discovery that cobalt additions of 2–20% significantly affect the morphology of aluminized coatings. To enrich the surface region of the Ni-Cr in cobalt, a layer of cobalt about (2–8) × 10-3 mm thick is applied by physical vapor deposition, sputtering or any other suitable process. The cobalt-coated substrate is heat treated using time-temperature conditions sufficient to cause the cobalt atoms to diffuse into the substrate to the required depth prior to the second step of aluminization. The desired cobalt concentration is greater than 2 wt.% in the substrate surface.Aluminization of the substrate after surface treatment with cobalt is achieved using conventional pack cementation or any other suitable process. It is shown that the oxidation resistance of Ni-20Cr is improved when this alloy is coated with a layer of cobalt of thickness 2.5 × 10-3mm, then heat treated for 5 h at 1160°C and finally pack aluminized.It is also shown that a duplex-aluminized physically vapor-deposited (PVD) NiCoCr coating has a significantly different morphology from a similarly aluminized PVD Ni-Cr coating.  相似文献   

12.
Duplex surface treatments via aluminizing and plasma nitriding were carried out on AISI 1045 steel. A number of work pieces were aluminized and subsequently plasma nitrided (Al–PN) and other work pieces were plasma nitrided and then aluminized (PN–Al). Aluminizing was carried out via pack process at 1123 K for 5 h and plasma nitriding was performed at 823 K for 5 h. The fabricated steels were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and microhardness testing. Tribological behaviors of the duplex treated AISI 1045 steels were examined against tungsten carbide pin using a pin-on-disc apparatus at room temperature. The PN–Al specimen showed higher surface hardness, lower wear rate and coefficient of friction than the Al–PN one. It was noticed from the worn surfaces that tribo-oxidation plays an important role in wear behavior of both specimens.  相似文献   

13.
The fine structure in the Fe-Al alloy layer of a new hot dip aluminized steel (HDA) was examined by means of X-ray diffractometry (XRD), electron diffraction technique, etc. The test results indicated that the Fe-Al alloy layer of the new aluminized steel mainly composed of Fe3Al, FeAl and α-Fe (Al) solid solution. There was no brittle phase containing higher aluminum content, such as FeAl3 (59.18% Al) and Fe2Al7 (62–93% Al). The tiny cracks and embrittlement, formerly caused by these brittle phases in the conventional aluminum-coated steel, were effectively eliminated. There was no microscopic defect (such as tiny cracks, pores or loose layer) in the coating. This is favourable to resist high temperature oxidation and corrosion of the aluminized steel.  相似文献   

14.
采用包埋铝和锌的方法在镁合金AZ91D表面制备了铝-锌合金化涂层,并且利用x射线衍射、能谱分析研究了该涂层的组织和耐腐蚀性能。该涂层外层为AlMg2Zn, Mg7Zn3 和Mg17Al12 金属间化合物层;内层为Mg17Al12金属间化合物分布于α-Mg晶界。研究表明,与镁合金基体相比较在质量分数为3.5wt.% NaCl扩渗层显示出较好的耐腐蚀性能。盐雾腐蚀说明,Al-Mg-Zn合金化扩渗层对于降低腐蚀速率起到有效作用。此外,合金化扩渗层与基体的结合是冶金结合,且涂层的显微硬度显著提高。  相似文献   

15.
Plain carbon steels are not suitable for nitriding as they form an extremely brittle case that spalls off readily, and the hardness increment of the diffusion zone is small. In this research, the effect of plasma nitriding time and temperature variation on the microstructure of the pack cemented aluminized plain carbon steel is investigated. All samples were aluminized at 900 °C for 2 h; the aluminized samples were subsequently plasma nitrided at 500 °C, 550 °C and 600 °C for 2.5, 5, 7.5 and 10 h. The phases formed on the sample surface were detected by X-ray diffraction (XRD). The cross section and samples surface were investigated by optical and scanning electron microscopy (SEM). Microhardness test was conducted to determine hardness change from the surface to the sample core. Results showed that by aluminizing the steel, Fe3Al phases as well as Fe–Al solid solution were formed on the surface and some aluminum rich precipitates were formed in solid solution grain boundaries. Plasma nitriding of the aluminized layer caused the formation of aluminum and iron nitride (AlN, Fe4N) on the sample surface. Consequently, surface hardness was improved up to about eight times. By increasing the nitriding temperature and time, aluminum-rich precipitates dissociated. Moreover, due to the diffusion of nitrogen through aluminized region during ion nitriding, iron and aluminum nitrides were formed in aluminized grain boundaries. Increasing nitriding time and temperature lead to the growth of these nitrides in the grain boundaries of the substrate. This phenomenon results in the increment of sample hardness depth. Plasma nitriding of aluminized sample in low pressure chamber with nitrogen and hydrogen gas mixture reduced surface aluminum oxides which were formed in aluminizing stage.  相似文献   

16.
High temperature oxidation and hot corrosion properties of Ir–Ta coated and aluminized Ni-base superalloys are presented. An Ir–Ta binary alloy, proposed as a novel metallic bond coat material, was coated on a Ni-base single crystal superalloy TMS-75 using electron beam physical vapor deposition, followed by a conventional low activity Al pack cementation process. Cyclic oxidation tests and hot corrosion tests revealed that these Ir–Ta coated and aluminized specimens showed reasonably good oxidation and hot corrosion resistance. In addition, it was found that the formation of TCP phases is suppressed by the presence of the Ir–Ta enriched layer. These results indicated that the Ir–Ta alloy system is promising as a new metallic bond coat material for high temperature structural materials.  相似文献   

17.
Oxidation Resistance of the Aluminide Coating Formed on Carbon Steels   总被引:6,自引:0,他引:6  
Low and medium carbon steels were aluminized by the pack aluminizing technique using halideactivated pure-Al and Fe-Al packs. The effect of mixture composition, aluminizing temperatureand time and C content of the steel substrate on the structure and thickness of the aluminidelayer, and on the oxidation resistance was investigated. The optimum oxidation resistance canbe achieved with a low carbon steel substrate when the intermetallic phases Fe3Al and FeAlform the surface of the aluminide layer. In this case, the Al concentration at the surface of thealuminide coating is at least ≥15 wt pct. Formation of high Al concentration phases (FeAl3 andFe2Al5) during aluminizing should be avoided as they tend to embrittle the aluminide layer andreduce its oxidation resistance.  相似文献   

18.
Titanium aluminides are considered as replacements for superalloys in applications in gas turbine engines because of their outstanding properties. Ti3Al has a superior creep strength up to 815° C, but has poor oxidation resistance above 650° C. Two approaches can be followed to improve the oxidation resistance of Ti3Al above 650° C. One is alloying and the other obtaining a protective surface coating. Niobium was found to improve the oxidation resistance, when added as an alloying element. Recent investigations showed that a TiAl3 surface layer considerably improves the oxidation resistance of titanium. In the present work, a TiAl3 layer was obtained on a Ti-14Al-24Nb (wt%) alloy using a pack aluminizing process. The cyclic oxidation behaviour of aluminized and uncoated samples was evaluated.  相似文献   

19.
为提高高温抗氧化性能,对HP40Nb钢进行了热浸镀Al-10%(质量分数)Si,并进行不同温度扩散处理,研究了不同扩散处理试样在1000℃条件下的高温氧化行为,通过SEM,EDS和XRD分析了经不同扩散处理后的渗层在高温氧化过程中的组织结构变化.结果表明:经800℃/4h扩散处理,渗层由内层(NiAl+ Cr3 Si)...  相似文献   

20.
High temperature oxidation and hot corrosion properties of Ir–Ta coated and aluminized Ni-base superalloys are presented. An Ir–Ta binary alloy, proposed as a novel metallic bond coat material, was coated on a Ni-base single crystal superalloy TMS-75 using electron beam physical vapor deposition, followed by a conventional low activity Al pack cementation process. Cyclic oxidation tests and hot corrosion tests revealed that these Ir–Ta coated and aluminized specimens showed reasonably good oxidation and hot corrosion resistance. In addition, it was found that the formation of TCP phases is suppressed by the presence of the Ir–Ta enriched layer. These results indicated that the Ir–Ta alloy system is promising as a new metallic bond coat material for high temperature structural materials.  相似文献   

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