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采用粒状渗剂分别在渗硼硅温度为850、900、950℃,保温时间为2、8 h的工艺参数下对纯镍表面进行固体渗硼硅处理。用光学显微镜(OM)对渗层横断面进行了显微组织观察,用显微硬度计测试渗层的硬度分布,用M200型磨损试验机研究未渗硼硅和渗硼硅纯镍的耐磨性,采用循环氧化试验研究未渗硼硅和渗硼硅纯镍的抗高温氧化性。结果表明,纯镍渗硼硅后,渗层为硅化物层和硼化物层,且硅化物和硼化物的显微硬度都大于基体硬度,渗层厚度随着渗硼硅时间和温度的增加而增加,其范围约为36~237?m,用X射线衍射仪(XRD)分析出渗层为硼化物层(Ni2B)和硅化物层(Ni3Si、Ni5Si2和Ni2Si)。磨损试验结果表明渗硼硅后试样的耐磨性得到提高。抗高温氧化试验结果显示未渗硼硅纯镍试样抗高温氧化性优于渗硼硅后纯镍试样。 相似文献
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以煤矸石为主渗剂,采用粉末包埋技术在纯铜表面制备渗硅层。采用金相显微镜和XRD对渗硅层组织结构进行检测分析,并对其硬度、耐蚀性、高温氧化性进行了测试。结果表明,煤矸石渗硅层中有Cu9Si、 Cu0.83Si0.17、Cu4Si和Cu3Al等新相生成;渗硅层主要由共析体(α+γ2)和α相组成,厚度可达600 μm,与基体结合紧密;煤矸石渗硅层洛氏硬度为118 HRF,而纯铜仅为51.5 HRF,其显微硬度最高可达320 HV0.05;渗硅层耐酸、盐、海水腐蚀分别较基体提高了2.25倍、2.58倍、2.97倍;抗高温氧化能力较基体提高了9.36倍。因此,煤矸石渗硅可在一定程度上提高纯铜耐蚀性和抗高温氧化性。 相似文献
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采用反应铸渗法在钢基体表面制备一层三元硼化物硬质覆层材料,研究了铸渗三元硼化物覆层与钢基体界面区的显微硬度,用SEM-EDS研究了界面的显微组织结构和元素分布,对铸渗反应机理进行了初步讨论。研究结果表明,通过反应铸渗法制备的三元硼化物硬质覆层-钢基体界面处存在一个由覆层高硬度到钢基体低硬度的狭窄的过渡区。显微组织观察与成分分析表明,覆层与钢基体在界面结合处实现了合金元素的扩散与渗透,并且两者形成了良好的冶金结合。 相似文献
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采用反应铸渗法存钢基体表面制备一层三元硼化物硬质覆层材料,研究了铸渗三元硼化物覆层与钢基体界面区的显微硬度,用SEM-EDS研究了界面的显微组织结构和元素分布,对铸渗反应机理进行了初步讨论.研究结果表明,通过反应铸渗法制备的三元硼化物硬质覆层.钢基体界面处存在一个南覆层高硬度到钢基体低硬度的狭窄的过渡区.显微组织观察与成分分析表明,覆层与钢基体存界面结合处实现了合金元素的扩散与渗透,并且两者形成了良好的冶金结合. 相似文献
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采用固体粉末法在GCr15钢表面进行渗铬处理,研究了不同渗铬时间下渗层的结构和性能,并研究了自然时效对渗层结构、力学性能的影响。采用扫描电子显微镜及EDS能谱仪、X射线衍射仪研究了时效前后渗层组织结构的变化,采用显微硬度仪、纳米压痕仪、洛氏硬度计分析了时效前后渗层表面硬度、截面微区硬度、与基体的结合强度。结果表明:渗层主要由Cr_2N、(Cr,Fe)_(23)C_6和(Cr,Fe)_7C_3相组成,渗层外表面为不连续的氮化铬晶粒分布在疏松的碳化铬中,随着渗铬时间的增加,氮化铬晶粒长大;渗层下表面为碳化铬层,由外向内Cr逐渐减少,Fe逐渐增加,形成了梯度过渡层结构。渗层表面显微硬度(HV_(0.05))在14 920~16 980 MPa之间,经过1a自然时效后表面显微硬度稍有降低;截面纳米硬度表明,随着Cr含量逐渐减少,纳米硬度也相应下降。洛氏压痕结果表明,压痕周围存在放射性裂纹及不同程度的渗层剥落现象;经过1a自然时效后压痕周围只存在放射性裂纹,渗层与基体结合强度提高。 相似文献
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通过负压铸渗法在铸铁表面制备FeCr复合渗层.经过组织分析、硬度测试、三点弯曲试验对渗层的性能以及渗层与基体的结合强度进行测试.结果表明:渗层组织比较致密,硬度远高于基体,渗层与基体结合良好. 相似文献
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采用双层辉光等离子表面冶金技术在γ-TiAl合金表面进行Ni-Cr共渗处理,形成均匀致密的Ni-Cr合金层,通过SEM、EDS、XRD等对其渗层显微组织、化学成分和相结构进行分析,并测试了合金层的显微硬度及耐磨性。结果表明,合金层有效渗层厚度为25μm,主要由Cr2 Ti、AlTi、Cr、NiTi2、Cr1.75 Ni0.25 Ti等相组成;合金层中合金元素Cr和Ni由表及里呈梯度分布,合金层与基体结合牢固;合金层的显微硬度、动态硬度及摩擦磨损性能显著高于基体。 相似文献
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MA Xiao-xia LIANG Wei ZHAO Xing-guo SHI Ju-yan BIAN Li-ping School of Materials Science Engineering Taiyuan University of Technology Taiyuan China 《材料热处理学报》2004,(5)
TiAl-based alloys are of great interest as an ideal hightemperature structural material due to their light weightrelatively good high temperature properties,howeverthe poor ductility at room temperature and insufficienoxidation resistance at high temperature are two factorsthat inhibit their practical applications.With theimprovement in ductility and fracture toughness atroom temperature[1],It is necessary to improve theoxidation resistance at high temperature.There are twokinds of improvement… 相似文献
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The microstructures of the siliconized specimens of Ti-48Al alloy were analyzed by SEM equipped with XEDS.The specimens were pack siliconized with the two different cementations, 15%Si+85% Al2O3 and 15%Si+85%ZrO2. The results show that a composite siliconized layer is formed on the surface of the TiAl alloy. The outer layer is the continuous Al2O3 where a lot of Si particles adhered; the inner layer is most of Ti5Si3 with amount of Al2O3 particles dispersed in. It was deduced that the Al2O3 in the cementation layer is formed by the Al atoms in the TiAl substrate react with the residual O in the furnace and in the TiAl substrate. 相似文献
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采用涂刷法和包埋法在渗硅石墨基体表面制备了双层结构的ZrB2-SiC-La2O3/SiC防护涂层,与表面无包覆涂层的渗硅石墨作对比,采用三点弯曲实验方法研究了热震对其力学性能的影响。结果表明,1500℃到室温之间循环热震10次后,表面无包覆涂层的样品单位面积氧化失重为52.1 mg/cm2,弯曲强度保持率仅为52.0%;而包覆涂层样品单位面积氧化增重为5.6 mg/cm2,弯曲强度保持率达78.5%,包覆ZrB2-SiC-La2O3/SiC涂层的样品热震后能保持良好的力学性能。在热震过程中ZrB2-SiC-La2O3/SiC涂层氧化生成的氧化层可有效地保护石墨基体不被氧化,避免了样品内部各种缺陷的产生,从而提高了其弯曲强度。 相似文献
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W. Liang X.X. Ma X.G. Zhao J. Zhang D.X. ZouSchool of Materials Science Engineering Taiyuan University of Technology Taiyuan China Central Iron & Steel Research Institute Beijing China 《金属学报(英文版)》2003,16(6):466-472
The Ti-48Al alloy was pack siliconized with 15%Si+85%Al2O3. The microstructure of the siliconized coating on the TiAl-based alloy was analyzed and its effect on oxidation resistance was investigated. The specimens before and after cycle oxidation were examined by XRD and SEM equipped with XEDS. The results showed that the coating is composed of a thin Al2O3 outer layer and a composite inner layer of Ti5Si3 with an appropriate amount of Al2O3 dispersed in. Cycle oxidation tests showed that the high temperature oxidation resistance of TiAl-based alloy was greatly improved by forming such composite coating. No spaliation and crack happened and the weight gain was very small after cycle oxidation at 900℃ for 314h. 相似文献
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分别采用液相渗硅法和原位反应法制备了硅化石墨,讨论了石墨基体密度和渗硅方法对硅化石墨力学性能和摩擦性能的影响。结果表明:两种方法都能明显提升石墨的抗弯强度,液相渗硅法制得的硅化石墨表面有一层浓度梯度分布的SiC层,石墨基体的耐磨性能得到明显改善。综合力学性能和摩擦性能考虑,选择低密度的石墨通过石墨化处理并采用液相渗硅法可以制备得到性能更优的硅化石墨。 相似文献
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铜表面气体渗硅涂层的抗氧化性能研究 总被引:5,自引:0,他引:5
对用硅烷-氢(SiH4/H2)混合气体在Cu表面进行化学热处理获得的含硅涂层进行了抗氧化性研究.结果表明,纯铜表面含硅涂层的形成提高了材料的抗氧化性能.对含硅铜涂层的氧化机理进行了探讨. 相似文献
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An oxidation test with rapid temperature cycling was developed to evaluate small coated parts. The samples in the form of wire or foils are resistively heated with a high-current AC power supply, allowing fast heating and cooling of the samples. Fast temperature cycling of the samples permits to complete more than 100 cycles in one day. A variety of steels coated with silicon diffusion coatings were tested and the results compared with oxidation via traditional thermal cycling. The test accurately predicts enhanced performance for siliconized 1010 steel, an increase by a factor of three for the life of siliconized 302 stainless steel, and an inadequate siliconized coating for 410 stainless steel. Details of the rapid temperature cycling apparatus as well as testing of the coated steels are described in the paper. 相似文献
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The surface alloying of Si into SUS430 and SUS304 stainless steels was achieved by a pack-cementation method. A high-temperature corrosion test was undertaken under a corrosive ash in a high-temperature gas, which simulated the environment of a waste incinerator. The effect of the surface alloying of Si on the high temperature corrosion resistance of these stainless steels was examined. The result of the corrosion test showed that the corrosion mass loss of the siliconized stainless steel was lower than that of non-treated stainless steel. It was thought that the high temperature corrosion resistance in the corrosive ash containing large amounts of molten salt was improved by the surface alloying of Si. The change in corrosion loss with test time in the corrosive ash was also examined. The corrosion loss of the non-treated stainless steels rapidly increased. On the other hand, the corrosion rate of the siliconized stainless steels was small.It was found from the observation and EPMA analysis of a cross-section of the specimen after the corrosion test that, for the non-treated stainless steels, the metallic elements were dissolved into the molten salt. On the other hand, for the siliconized stainless steels, a scale consisting of silicon oxide was formed on the steels. As a result, the dissolved metallic elements were small.The electrochemical studies indicated that there was an effect of the surface alloying of Si on the hot corrosion resistance of the stainless steels. Hence, the corrosion potentials of the siliconized steels were higher than those of the non-treated steels. The increase in the anodic current densities for the siliconized steels was smaller than that for the non-treated steels. It was thought that the electrochemical corrosion reaction was difficult to occur due to the surface alloying of Si into the stainless steels. 相似文献
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In order to improve the oxidation resistance properties of 30 at.% Mo5Si3/MoSi2 composite at high temperature in air, a molybdenum disili-tide coating was prepared on its surface by a molten salt technology. XRD and SEM analysis showed that only tetragonal MoSi2 phase ex-isted in the coating after being siliconized for 5 h at 900℃. The oxidation film formed on the uncoated sample was not dense, so that oxygen diffused easily through it. The volatilization of MoO3 resulted in the oxidation film separating from the substrate. The MoSi2coating was proved to be an effective method to prevent 30 at.% MosSi3/MoSi2 composites from being oxidized at 1200℃. A dense glassy SiO2 film was formed on the MoSi2 coating surface, which acted as a barrier layer for the diffusion of oxygen atoms to the substrate. The 30at.% Mo5Si3/MoSi2 composites with a MoSi2 coating showed much better oxidation resistance at high temperature. 相似文献