固态渗铝对AlCoCrFeNi高熵合金组织的影响

采用固态渗铝法在AlCoCrFeNi高熵合金表面制备了铝化物渗层。渗铝温度为900 ℃,时间为4 h。借助SEM、EDS、XRD和显微硬度计分析了渗层的显微组织、相组成和显微硬度。结果表明,铝化物渗层分为内外两层,基本无孔洞和裂纹,与基体结合良好。铝化物渗层的硬度达970 HV0.1,远高于基体。     

纯镍渗硼硅处理工艺及组织性能研究

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。     

工业纯铜煤矸石渗硅层制备工艺及耐蚀性研究

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、 Cu_0.83Si_0.17、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。     

铸渗法制备三元硼化物硬质覆层-钢基体界面特性的分析

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。     

铸渗法制备三元硼化物硬质覆层一钢基体界面特性的分析

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.     

固体渗铬层组织结构及性能稳定性研究

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。     

纯镁表面真空扩散渗铝层的组织和性能

采用真空扩散渗铝的方法,在445 ℃对纯镁进行了表面合金化改性处理.采用金相显微镜、XRD、EDS和显微硬度测试等方法对渗层进行了组织结构和显微硬度分析.结果表明,经表面合金化处理,在纯镁表面获得了均匀致密的渗铝层,渗层中有大量的金属间化合物β-Mg17Al12生成,渗层与基体之间为冶金结合,材料表层的显微硬度有很大提高.     

负压铸渗法制备铸铁表面FeCr复合渗层的组织及性能研究

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.     

钛合金表面原位合成TiN渗镀层摩擦性能研究

采用双层辉光离子渗金属技术在钛合金TC11表面原位合成TiN渗镀层以提高其耐磨性。利用OM、SEM、EDS、XRD对TiN渗镀层的形貌、组织成分、相结构进行分析;通过显微硬度、划痕试验对TiN层力学性能进行研究;通过常温磨损试验研究了TC11合金表面TiN渗镀层摩擦磨损行为及机理。结果表明,在常温磨损试验条件下TiN层摩擦系数下降一半,表现出较好的减磨耐磨性能;渗镀层显微硬度达到1400HV0.2;渗镀层与基体结合力为45N,结合强度高。     

γ-TiAl合金表面辉光等离子Ni-Cr共渗层的组织与性能

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。     

Study on the Formation Mechanism of the Solid Siliconized Layer on TJ-48A1 Alloy

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…     

Study on the Formation Mechanism of the Solid Siliconized Layer on Ti-48Al Alloy

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.     

热震对包覆ZrB2-SiC-La2O3/SiC涂层渗硅石墨力学性能的影响

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。     

Cr18Ni9奥氏体不锈钢表面渗硅层及脆性相分析

采用粉末包埋法对Cr18Ni9奥氏体不锈钢表面进行渗硅处理后,除获得致密的渗硅层外,还观察到脆性很大的高硅相。应用SEM电镜分析、能谱分析和场发射高分辨率扫描电镜等方法分析了渗硅层的成分、组织和形貌,以及渗层表面脆性相的形成及其原因。分析表明,Cr18Ni9钢渗硅层中脆性相出现在含硅量20％（原子分数）以上,其脆性源于冷却过程中高硅相周边调幅分解产物的强力约束和DO3有序相晶格常数的持续减小。     

FORMATION OF SILICONIZED LAYER ON TiAI-BASED ALLOY AND THE OXIDATION RESISTANCE

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.     

液相渗硅法和原位反应法制备硅化石墨及性能研究

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。     

铜表面气体渗硅涂层的抗氧化性能研究

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.     

A rapid-temperature-cycling apparatus for oxidation testing

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.     

Formation of Si diffusion layer on stainless steels and their high temperature corrosion resistance in molten salt

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.     

MoSi2 oxidation resistance coatings for Mo5Si3/MoSi2 composites

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.