Nature and Growth of Interaction Layers Formed during the Reaction between Solid Ni and Liquid Al

The nature and growth of the interaction layers between solid Nb and liquid Al has been studied by carrying out the tests on Nb(s)-Al(l)and Nb(s)-Al(l)-Ni(s) reaction couples isothermally reacted between 700℃and 900℃for different time intervals.It has been found that the interaction layer between Nb and Al contains two parts:a thin continuous layer of NbAl3 adjacent to the Nb surface and a two-phase zone constituted of NbAl3 particles dispersed in an Al matrix.Although the nature and growth of interaction layers follows the sour-stage mechanism,a typical cruciform pattern does not occur in Nb(s)-Al(l) reaction couples.However,a cruciform pattern was observed in Nb(s)-Al(l)-Ni(s)reaction couples.The movement of NbAl3 particles is important to the production of cruciform pattern in the reaction couples.     

渗铝涂层对Ni_3Al－Mo基合金高温氧化的防护作用及机理

采用高活度渗铝工艺在ＩＣ－６（Ｎｉ３Ａｌ－Ｍｏ基）合金表面获得内扩散型渗铝涂层，在氮气环境下对渗铝涂层进行扩散处理．利用光学显微镜、ＳＥＭ、ＥＰＭＡ、ＸＲＤ分析研究了涂层的成分及组织结构，测定表明，涂层中的钼以Ｍｏ３Ａｌ沉淀相的形式存在．等温氧化及循环氧化实验表明，渗铝涂层的抗高温氧化性能明显优于ＩＣ－６合金；保护性的Ａｌ２Ｏ３氧化膜阻止了钼的氧化物的形成，避免了ＩＣ－６合金在循环氧化中出现的ＮｉＭｏＯ４相的多晶型转变，显著改变了合金的抗循环氧化能力；涂层经１０００℃、３００ｈ等温氧化及１０００℃、１００ｈ循环氧化后，未出现β－ＮｉＡｌ相的分解，可认为涂层具有较强的保护作用。     

自修复三氧化二铝涂层研究

结构材料表面涂层是解决聚变堆液态金属自冷却包层中的磁流体动力学压降(MHD)的主要方法之一.探讨了在包层结构材料表面直接形成电绝缘三氧化二铝涂层的液体渗铝法,并对渗层结构和表面三氧化二铝的形貌和成分分布进行了多种电子显微分析.研究结果表明:液体渗铝法是制作自修复三氧化二铝涂层的可靠方法,但渗铝和氧化工艺对涂层性能影响较大.     

机械能辅助渗铝工艺及渗铝层性能研究

机械能辅助渗铝是将机械能与热能相结合一种新渗铝工艺,可以将渗铝温度降低到560～650 ℃.本文通过实验对机械能辅助渗铝工艺进行了研究,对主要工艺参数进行了优化,获得了组织致密、渗层厚度≥60 μm、以Fe2Al5相为主要组成相的渗铝层,并研究了渗铝钢的抗高温氧化性能及机械性能.     

The Effect of the Thickness of Fe2 Al5 Phase Layer at Fe/Al Interface on the Mechanics Behavior of Hot Dip Aluminizing Coating

Hot Dip Aluminized Coatings with different thickness were prepared on Q235 steel in aluminum solutions with different temperature for certain time. Through tensile tests and in-situ SEM observations, the effect of the coating's microstructure on the tensile strength of the samples was studied. It was disclosed at certain aluminum solution temperature,transaction layers mainly composed of Fe2 Al5 phase got thicker with time prolonging, and this changed initial crack's extending direction from parallel with to vertical with stretching direction. The change in crack direction decreased tensile strength of samples, thus made the coating easy to break. It was concluded that the existence of thick Fe2 Al5 phase layer was the basic reason for the lowering of tensile strength of the coating.     

Effect of Al on High-Temperature Oxidation of Cr–W Alloys

The effect of Al on the high temperature oxidation behavior of Cr–10 wt.%W alloy was investigated using a cyclical oxidation test at 1,000 °C in dry air. First, Al was added into the Cr–W alloy as an alloying element up to 8 weight percent. Although alloying with Al reduced the spalling, it did not eliminate it. Secondly, Al was applied to the surface using an aluminizing process. Forming an Al–Cr layer on the Cr–W alloy reduced oxidation rate significantly and eliminated spalling completely.     

GL渗铝钢渗层特征及其对焊接接头机械性能的影响

采用光学显微镜、扫描电镜(SEM)、电子探针(EPMA)和X射线衍射仪分析了感应料浆法(GL)渗铝钢管的金相特征和渗层相组成.结果表明,通过控制一系列渗铝工艺参数可以使渗铝层由α-Fe(Al)固溶体、Fe_3Al和FeAl构成,从而避免了因含铝较高的FeAl_2和Fe_2Al_5等脆性相而导致焊接性能恶化的问题,显著改善了渗铝钢的焊接性,使焊接接头的组织与性能容易得到保证.     

Cu-Al-Y合金稀土渗铝及内氧化研究

利用稀土化合物CeCl3对Cu-Al-Y合金表面进行催渗渗铝,采用工业N2中的余氧作为内氧化介质对Cu-Al-Y合金渗铝后的试样进行内氧化制备Al2O3/Cu复合材料的新方法,并进行了初步的试验研究与理论分析。结果表明:稀土化合物CeCl3在渗铝和内氧化过程中有着明显的促进作用,能在Cu-Al-Y合金表面得到一层均匀的渗铝层。内氧化后,能在渗铝层形成Al2O3弥散硬化层。     

Factors affecting the microstructure of platinum-modified aluminide coatings during a vapor phase aluminizing process

Platinum (Pt)-modified aluminide coatings were developed by electroplating a thin layer of Pt followed by an industrial vapor phase aluminizing process. The goal of this work was to systematically investigate the effect of critical coating process parameters (such as the electroplated Pt thicknesses, Al contents in Cr-Al nuggets, diffusion heat treatments) and substrates on the final Pt-modified aluminide coatings. Surface morphology and cross-section microstructure of the developed coatings were inspected and compared by using Optical Microscope, Scanning Electron Microscope (SEM) equipped with energy dispersive spectroscopy (EDS). Experimental results showed that the Al and/or Pt increase shall favor the formation of ξ-PtAl₂ phase; transformation of ξ-PtAl₂ into β-(Ni,Pt)Al phase can be obtained via a heat treatment process; Cr, Co elements in the studied Ni-base superalloy substrates did not show significant influence on coating outer layer microstructure; while substrate elements affect the microstructure of the coating interdiffusion layer.     

钢材热浸镀铝抗高温氧化的动力学研究

通过静态高温氧化试验,研究了纯铝、铝－3％硅、铝－7％硅和铝－9％硅4种镀层高温氧化的动力学特性,推导了动力学方程式的算法,计算了4种镀层的氧化激活能（Q）及其与镀液中硅含量的关系。结果表明：Q＝1029－3226kJ/kg,4种镀层在700-900℃时的氧化规律为非线性递增,纯铝镀的最高使用温度为900℃,对于铝－硅镀层,当镀液中含硅低于3％时的最高使用温度为800℃,高于3％时的最高使用温度为700℃。