不锈钢表面振动冲击加速渗铝工艺研究

研究了利用喷丸加速制备涂层技术,对1Cr18Ni9Ti不锈钢分别进行600℃×4、6和8 h渗铝处理,研究了1Cr18Ni9Ti试样的单位面积增重、Al涂层厚度、主要元素沿涂层截面的分布;并将不同温度下获得的铝化物涂层与空白试样一起进行了高温氧化测试实验(900℃×100 h)。结果表明,在较低的温度600℃和较短的时间4 h,可以在1Cr18Ni9Ti钢基体上形成35μm厚的铝化物涂层;但抗氧化性能测试结果却表明,振动渗制处理6 h获得的铝化物涂层性能优于处理4 h和8 h的涂层。     

The effects of ultrasonic nanocrystal surface modification (UNSM) on pack aluminizing for the fabrication of Pt-modified aluminide coatings at low temperatures

An 8–9 μm thick Pt layer was coated on a superalloy and transformed to a Ni–Pt alloy layer by the interdiffusion of Ni and Pt at 1050 °C for 3 h. The surface of the Ni–Pt alloy layer was pack aluminized to form a Pt-modified aluminide coating. Ultrasonic nanocrystal surface modification (UNSM) was applied to the alloy layer prior to pack aluminizing. The effects of UNSM on Pt-modified aluminide coatings fabricated at 750, 850, 950, and 1050 °C were studied. The treated Ni–Pt alloy layers had finer grain sizes than the untreated specimens. In addition, UNSM made the grain size of the Ni–Pt alloy finer and reduced the surface roughness. During pack aluminizing, the Pt-modified aluminide coatings fabricated following UNSM uptook more Al and were thicker than the untreated Pt-modified aluminide coatings at the various temperatures (750, 850, 950, and 1050 °C). The untreated Pt-modified aluminide coatings with pack aluminizing performed at 750 and 850 °C were composed of only a two-phase (NiAl + PtAl₂) layer, due to insufficient diffusion of Pt at the lower temperatures. However, two-phase and one-phase (NiAl) layers were obtained in the treated Pt-modified aluminide coatings which were pack-aluminized at 750, 850, 950, and 1050 °C, due to the diffusion of Pt through the greater amount of grain boundaries and increased volume generated by UNSM before the pack aluminizing. Additionally, the treated coatings had smoother surfaces even after the pack aluminizing. During cyclic oxidation at 1150 °C for 1000 h, the treated Pt-modified aluminide coatings aluminized at relatively low temperatures (750 and 850 °C) showed better cyclic oxidation resistance than the untreated Pt-modified aluminide coating aluminized at 1050 °C.     

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.     

Formation and Microstructural Characterization of Silicon-modified Aluminide Coating on Nickel-based Superalloy IN738LC

ALUMINIDE COATINGS are used extensively forprotecting gas turbine hot section components due totheir high oxidation resistance and low capital cost.However,for some application,their properties must bemodified by adding elements such as Cr,Si and Pt tomeet high performance gas turbines requirements[l,2].Although silicon is less efficient as a protective scaleformer than chromium and aluminum,silicon-modifiedaluminide coatings,have shown better hot corrosionresistance(specially to type …     

TC4钛合金表面B-Al复合渗层的组织和性能

采用固体粉末包埋渗两步法,在TC4钛合金表面先1050 ℃渗硼 4~6 h再950~1050 ℃渗铝 4 h制备出B-Al复合耐磨渗层。利用X射线衍射仪(XRD)、扫描电镜(SEM)、波谱仪(WDS)和能谱仪(EDS)、显微硬度仪和摩擦磨损试验机对复合渗层的物相组成、显微组织、微区成分、表面硬度和摩擦因数进行测试和分析。结果表明:B-Al复合渗层厚为37~115 μm,主要由TiB₂相和TiAl₃相组成,外层是弥散分布TiB₂的TiAl₃层,向内依次形成厚度较小的TiAl₂、TiAl及Ti₃Al等Ti-Al金属间化合物层。B-Al复合渗层表面硬度为1041.7~1429.4 HV0.1,约为TC4钛合金硬度的3.03~4.16倍;经1050 ℃×6 h渗B后1050 ℃×4 h渗Al,其摩擦因数约为0.3,较TC4钛合金基体下降约25%。     

简单/改性铝化物涂层的研究现状

航空发动机各部件高温结构材料在苛刻环境下服役时,会遭受严重的高温氧化和热腐蚀.在合金表面施加铝化物涂层后,高温下表面能够生成一层致密且生长缓慢的Al2O3氧化膜,从而隔绝腐蚀介质,以防止合金被快速氧化腐蚀.概述了铝化物涂层的优点,包括制备简单、成本低廉.重点综述了以Ni、Fe、Ti/TiAl为合金基体的铝化物涂层微观结构.涂层的微观结构主要由渗铝工艺、基材成分及后处理工艺等因素决定,渗铝工艺包括渗剂成分、渗铝温度和渗铝时间.在高温下渗铝,Al的活度较低,涂层主要以基体元素向外扩散形成外扩散型涂层为主;在低温下渗铝,Al的活度较高,涂层主要以Al向内扩散形成内扩散型涂层为主.还归纳了不同渗铝涂层在干燥空气和水蒸气环境中的高温氧化行为,阐述了水蒸气对铝化物涂层高温氧化行为的影响,比较了Ni-Al系和Fe-Al系涂层的抗高温氧化性能.同时介绍了Cr-Al、Si-Al和Pt-Al 3种改性铝化物涂层的研究进展,包括制备方法、微观结构及抗高温氧化和腐蚀性能.最后,展望并总结了高温防护涂层的发展趋势.     

包渗温度对Ti-Al渗层组织和耐磨性能的影响(英文)

为了提高纯铜表面的耐磨性能,采用电镀/浆料包渗相结合的方法,以TiO2粉为渗Ti源,纯Al粉为还原剂,在Cu表面预镀Ni随后表面浆料包渗Ti-Al,制备Ti-Al共渗层。研究了包渗温度对Ti-Al渗层组织和耐磨性能的影响。采用SEM和XRD分析了渗层表面形貌和结构。结果表明:在800～950°C共渗12 h时,随着温度的升高,渗层组织变化过程为NiAl+Ni3(Ti,Al)→NiAl+Ni3(Ti,Al)+Ni4Ti3→Ni4Ti3+NiAl→NiAl+Ni3(Ti,Al)+NiTi;Ti-Al渗层的摩擦因数随着包渗温度的升高而降低,最小摩擦因数约为纯铜的1/3,最小硬度为纯铜的5倍。     

OXIDATION RESISTANCE OF NANOCRYSTAL ODS ALUMINIDE COATINGS PRODUCED BY PACK ALUMINIZING PROCESS ASSISTED BY BALL PEENING

Nanocrystal ODS （oxide dispersion strengthening） aluminide coatings were produced on a stainless steel and nickel-based superalloy by the pock aluminizing process assisted by ball peening, Pure Al powders and 1% of ultra-fine Y2O3 powders were mixed by ball milling. The ultra-fine Y2O3 powders were dispersed in Al particles. Ball peening welded the Al particles onto the substrate and accelerated the formation of aluminide coating. Nanocrystal ODS aluminide coatings were produced by the outward growth at a much low temperature （below 600℃） in a short treatment time. The effects of the operation temperature and treatment time on the formation of the coatings were analyzed. SEM （scanning electron microscope）, AFM （atomic force microscope）, EDS （energy dispersive X-ray spectroscopy）, XRF （X-ray fluorescence spectrometer） and XRD （X-ray diffraction） methods were applied to investigate the microstructure of the coatings. High-temperature oxidation tests were carried out to evaluate the oxidation resistance of the ODS aluminide coatings.     

分散剂Y2O3对渗铝层的影响

通过改变传统渗剂来研究分散剂（Al2O3，Y2O3）在渗铝过程中的作用和对渗铝层的影响。利用XRD和SEM对渗层相的组成、氧化前后表面形貌进行分析。结果表明：分散剂Y2O3在最初的渗铝过程中参加了渗铝过程，不仅防止铝粉粘结，而且影响渗层相的组成。分散剂为Al2O3时，渗层主要为Al3Ti＋AlTi＋AlTi3相，而分散剂中含有Y2O3时，渗层土要为AlTi3相，这与传统渗铝机理认为分散剂在渗铝过程中不参加渗铝反应相矛盾。同时，分散剂也影响着渗铝层氧化前后的表面形貌及Al2O3的晶格类型。     

Evaluation of aluminide diffusion coatings for thermal cyclic oxidation protection of a nickel‐base superalloy

Active element modified aluminide diffusion coatings on IN738 substrates were produced by a new route using continuously cast, aluminum alloy wires consisting of Al‐Y, Al‐Ce, Al‐La and Al‐Si‐Y. The cast wires were used as evaporation sources for ion‐vapour deposition followed by diffusion heat treatments to form nickel aluminide coatings. In order to examine the oxidation resistance of these coatings at elevated temperatures, thermal cyclic oxidation experiments were carried out in air at 1050°C. While all coatings were found to provide significant protection, the Al‐La modified coatings provided the greatest resistance to cyclic oxidation. On the other hand, with coatings based on Al‐Si‐Y alloys, while silicon has a strong ability to reduce the outward diffusion of aluminum, the adverse effect of silicon on mechanical properties of the coating, together with the formation of volatile silicon monoxide, led to catastrophic localized oxidation of the protective coatings.     

Structure and cyclic oxidation resistance of Pt, Pt/Pd-modified and simple aluminide coatings on CMSX-4 superalloy

The coatings were prepared by the means of Pt and Pt/Pd galvanizing, followed by vapor phase aluminizing at 1050 °C. Microstructural and phase analysis revealed that all the investigated coatings consisted mainly of β-NiAl phase, however the Pt-modified aluminide coating also contained PtAl₂ phase and pure platinum precipitates. The cross-sectional microstructure of the coatings was zonal and composed of β-NiAl phase zone and the diffusion zone. The Pt modified aluminide coating's cross-section also incorporated an outermost zone consisting of β-NiAl and PtAl₂ phases. The concentration profiles proved that both Pt and Pd contents decrease gradually inwards the modified coatings. Cyclic oxidation tests at 1100 °C proved that Pt/Pd-modified aluminide coatings exhibit the best performance under cyclic conditions. The analysis of oxidation kinetics curves showed that the course of simple aluminide coating's oxidation is slightly different from that of Pt- and Pt/Pd-modified aluminide coatings.     

一种可内生Al2O3扩散障的δ-Ni2Al3-Cr2O3/ Ni-Cr2O3涂层体系

通过对Ni-Cr₂O₃复合镀层620 ℃部分渗铝制备了δ-Ni₂Al₃-Cr₂O₃/Ni-Cr₂O₃涂层体系。Cr₂O₃颗粒在渗铝的过程中和Al反应生成更为稳定的Al₂O₃。1000 ℃恒温氧化20 h后发现,铝化物涂层和复合镀层内掺杂的Cr₂O₃颗粒完全转化为Al₂O₃,并在铝化物涂层/Ni镀层界面自发形成了一层Al₂O₃富集层,该富集层起扩散障作用,阻碍铝化物涂层因互扩散所致的退化。     

The Effect of NiAl Coatings on Oxidation Behavior of AISI 403 Stainless Steel

STAINLESS STEEL TYPE AISI403possess a highdegree of resistance to atmospheric corrosion becauseof its ability to form a dense adherent oxide film,whichprotects the material from further attack[1].Thiscomposition was developed to meet the requirementsfor some gas turbine components.The alloy is notparticularly recommended for use in hot corrosion andoxidation environments.Therefore,a protective coatinglayer is essential for such applications as hot sectioncomponents in gas turbine[2].A…     

The role of combustion synthesis in the formation of slurry aluminization

Slurry processes have been investigated for several years as an alternative technique to conventional CVD-derived aluminizing to achieve similar diffusion coatings. This study investigates the coating formation mechanisms during heat treatment processes on pure nickel using slurries, which contain high amounts of micro-sized aluminium particles. At temperatures in the range of 550 °C–1000 °C, aluminium diffuses into the nickel substrate, promoting the formation of intermetallic nickel–aluminide layers. In order to control this process, it is important to understand the mechanisms that occur in the initial stages, when the metallic aluminium powder melts and reacts in contact with nickel. While a conversion of closely pressed nickel–aluminium into aluminide by combustion synthesis is well known, DTA measurements were undertaken to investigate if and when such processes occur in loosely packed powders. Two compositions of nickel with aluminium or eutectic aluminium–silicon alloyed particles were used in order to reveal a potential influence of the melting point of the aluminium alloy particles. The influence of the atmosphere was studied by comparing results during exposure in argon and air. Subsequently, for comparison with the more complex mechanism of slurry aluminizing, both powders were applied to pure nickel substrate and the coating formation during heat treatment at 600 °C, 650 °C, and 700 °C was investigated. The results clearly show the importance of combustion synthesis on the formation of slurry coatings on nickel. Based on the observations, four steps were identified, which lead to the formation of aluminides and the subsequent growth of the aluminide layer: After melting of the aluminium powder, a network of molten aluminium forms within and between the particles, followed by dissolution of nickel in the aluminium melt. If enough Al is available, combustion synthesis between Ni and Al takes place. After this highly exothermic reaction, solid state diffusion controls the further formation of slurry coatings on nickel. Finally, the mechanism was verified by coating industrially used superalloys with the Al-based slurry in air and argon.     

Effect of Y2O3 or CeO2 Fillers on the Oxidation Behavior of Aluminide Coatings by Low-temperature Pack Cementation

利用Y2O3或CeO2纳米颗粒替代部分Al2O3粉作为填充剂,在Ni基体上, 于600 ℃低温渗铝10 h,制备了2种稀土氧化物改性的低温渗铝涂层。作为对比,采用相同的工艺在Ni基体上利用纯Al2O3粉制备了普通渗铝涂层。1000 ℃下恒温氧化结果表明：Y2O3通过抑制q-Al2O3的长大提高涂层的抗氧化性能,而CeO2则通过促进q-Al2O3向a-Al2O3的相变明显提高其抗氧化性能。文中对Y2O3或CeO2是如何影响渗铝涂层的氧化性能进行了分析。     

Aluminide Coatings Formed on Fe–13Cr Steel at Low Temperature and its Oxidation Resistance

A novel aluminizing process has been developed to produce aluminide coatings on Fe–13Cr stainless steel at a much lower temperature (520–600 °C) and with a shorter time (60–240 min) compared to the conventional pack-aluminizing processes. In this process, chemical reaction and atomic diffusion were accelerated by ball impact generated by mechanical vibration. The effects of operation temperature and duration on the coating thickness were studied. Scanning-electron microscopy (SEM and EDS) showed that the coatings appeared to be dense, homogeneous, free of porosity and with excellent adherence to the substrate. X-ray diffraction (XRD) analyses indicated that the coatings consisted mainly of η-Fe₂Al₅ and θ-FeAl₃. High-temperature oxidation tests were carried out in air at 900 °C. The results indicated that the aluminide coatings obtained from this process have significantly improved high-temperature oxidation resistance.     

Gas phase aluminizing of TiAl intermetallics

The aim of this study was the microstructural characterization of aluminide diffusion coatings deposited on Ti48Al2Cr2Nb and Ti46Al7Nb alloys. The coatings' deposition process was prepared using out of pack method. The X-ray diffraction phase analysis from the surface of coatings indicated that TiAl₂ phase dominates in the coating. The thickness of aluminide coating was about 10 μm.     

Preparation of aluminide coatings at relatively low temperatures

1 Introduction Protective coatings by pack aluminizing are frequently applied to metals to protect them from high temperature oxidation and hot corrosion attack [1, 2]. Pack aluminizing consists of heating the parts to be coated in a closed or vented pac…     

Formation of aluminide coatings on Fe-based alloys by chemical vapor deposition

Aluminide and Al-containing coatings were synthesized on commercial ferritic (P91) and austenitic (304L) alloys via a laboratory chemical vapor deposition (CVD) procedure for rigorous control over coating composition, purity and microstructure. The effect of the CVD aluminizing parameters such as temperature, Al activity, and post-aluminizing anneal on coating growth was investigated. Two procedures involving different Al activities were employed with and without including Cr–Al pellets in the CVD reactor to produce coatings with suitable thickness and composition for coating performance evaluation. The phase constitution of the as-synthesized coatings was assessed with the aid of a combination of X-ray diffraction, electron probe microanalysis, and existing phase diagrams. The mechanisms of formation of these CVD coatings on the Fe-based alloys are discussed, and compared with nickel aluminide coatings on Ni-base superalloys. In addition, Cr–Al pellets were replaced with Fe–Al metals in some aluminizing process runs and similar coatings were achieved.     

Oxidation of Simple and Pt-Modified Aluminide Diffusion Coatings on Ni-Base Superalloys—II. Oxide Scale Failure

The spallation behavior of oxides formed during isothermal oxidation at 1050°C of one simple (PWA73) and three Pt-modified (RT22, SS82A and MDC150L) aluminide diffusion coatings on the same Ni-base, single-crystalline superalloy (CMSX-4) was investigated by scanning electron microscopy (SEM) and transmission-electron microscopy (TEM). It was found that the main spallation mechanism was the formation of large Kirkendall voids at the oxide–coating interface. It is believed that the void formation was caused by counter-current flow of vacancies to the diffusion of Ni away from the interface as Al is consumed by the oxide. The magnitude of the vacancy current was determined by the oxidation rate. The properties of the void-formation mechanism are discussed in view of previous data on the microstructure of the oxide scales.