Eutectoid Magnetite in Wüstite Under Conditions of Compressive Stress and Cooling

During hot rolling, the existence of a wüstite layer is favored from the standpoint of improved descaling performance. In this work, the mutual effect of external compressive stress and cooling on the phase transformation of oxide scales formed on steel was investigated. Optical microscopy images showed that a fast cooling rate of about 80?°C/min promoted the formation of magnetite/Fe eutectoid. When applying a compressive stress, growth of the magnetite/Fe eutectoid was increased. It was inferred that the promoting effect of fast cooling rate on the diffusion is advantageous to the growth of magnetite/Fe eutectoid. The increase of system chemical potential by the compressive stress also promoted the growth of magnetite/Fe eutectoid.     

Microscopic Approach of Adhesion and Wetting of Liquid Metal on Solid Ionocovalent Oxide Surface

The adhesion and wetting of non-reactive liquid metals with solid ionocovalent oxides are studied on thebasis of the experimental work of adhesion W data obtained with the sessile drop method.An analysis of theexperimental W values of different liquid metals on various solid oxides is first performed to evidence the de-pendence of the work of adhesion of a metal/oxide system on the electron density of the metal and on thethermodynamic stability of the oxide.An electronic model is then proposed to describe the microscopic mech-anism of metal-oxide interactions.Based on the model,the contact angle and the work of adhesion of differentliquid metals on various solid oxides can be interpreted and estimated,and their correlations to the variousphysical quantities of the oxides can be easily deduced.The basic consideration of the model is that the adhe-sion between a metal and an oxide is assured by the electron transfer from the metal into the oxide valenceband which is not completely filled of electrons at high temperatures,and is enhanced when this electron trans-fer at the metal/oxide interface is intensified.The influence of interface defects on the wetting and adhesion issuggested and discussed.     

Potentialities of Raman Imaging for the Analysis of Oxide Scales Formed on Zircaloy-4 and M5® in Air at High Temperature

Micro-Raman imaging was used to investigate oxide scales formed on Zircaloy-4 and M5^® alloys in air, in the 800–1,000 °C temperature range. To create the 2D spectral images, the data were processed by different ways. The results clearly show that a microscopic picture of the scales in terms of microstructure and internal stresses can be developed from Raman spectral maps at the micron scale. Data on the microstructure, crystallography, and composition, are presented. They confirm that the crystallographic phases observed for the Zircaloy-4 and M5^® alloys are different, since, for Zircaloy-4, we clearly observed additional Raman signatures which most probably track the presence of nitrogen in the layers well before the occurrence of the kinetic transition. In particular, they show the presence of cubic zirconia in the layers, and strongly suggest the presence of zirconium nitride and oxynitride. Results also suggest the presence of strong stress gradients in the oxide scales.     

Diffusion Carbide Layers, Formed on the Surface of Steel in the Vacuum Titanizing Process

DIFFUSION TITANIZING is applied to increase thedurability of tools,which operate under wearconditions[1].There is considerable bibliographicaldata concerning the diffusion titanizing process,inparticular,problems connected with hard titaniumcarbide layers are quite well elaborated[2-4].In this paper,a novel vacuum titanizing process,which involves treating steel in titanium vapor at thetemperature over1000°C under low pressure,has beenproposed[5].A porous material containing titaniumw…     

Electrochemical Study on the Change in Valency of Niobium Oxide in the MnO-SiO_2-Nb_2O_5 System

Change in valency of Nb-oxide in MnO-SiO_2-Nb_2O_5 system was studied with the electrochemical method using ZrO_2 asthe solid electrolyte.Thermodynamic analysis has shown that the only possible reaction that could take place at the working elec-trode is:2(Nb_2O_5)=2(Nb_2O_4)+O_2 with the a_0 values experimentally evaluated,values of a Nb_2O:/a Nb_2O:were calculated andisoactivity-ratio curves drawn in MnO-SiO_2-Nb_2O_5 triangles at 1418 and 1585K.The simultaneous existence of tetra-andpenta-valent Nb mineral constituents in industrial Nb-bearing slags was thus verified experimentally.     

Study of the Structure of Oxide Interface in the Pt-Rh Alloy by AP-FIM

This paper reports the study of structure of oxide interface in Pt-Rh alloy by atom probe field ion micro-scope (AP-FIM) which is well suited for the study of atom distribution with atomic scale at the surface and in-terface of alloy. AP depth profiles show that oxide interface exist in the Pt-Rh alloy which consists of PtO,RhO, PrO_2 and RhO_2 . The mechanism of oxidation of the alloy is considered as that first oxygen moleculesadsorbed on-to the surface of alloy then dissociate into oxygen atoms (0_2→2O). Consequently oxygen atomsdiffuse into interior through grain boundary forming oxide (M+O→MO). When the concentration of oxygencontinuously increases the dioxide (MO+O→-MO_2) forms.     

Inhibition of the Corrosion of Iron in the pH Range 9.3–22.6: Effect of Tartrate Ions on the Thickening of the Oxide Film

Abstract

The inhibition of the corrosion of iron by 0·1 M sodium hydroxide and 0·1 M sodium tetraborate is accompanied by thickening of the air-formed oxide film, which is absent in the presence of 0·5 M sodium tartrate. It is concluded that in the pH range 9·3 – 12·6 general film thickening is not a necessity for inhibition, but arises as a consequence.     

Influence of Irradiation on the Oxide Film Formed on 316 L Stainless Steel in PWR Primary Water

Oxidation of stainless steel in PWR primary water at 325 °C was studied by investigating the influence of defects created at the alloy subsurface by proton irradiation before corrosion exposure. Corrosion experiments were conducted by sequentially exposing samples, with H ₂ ¹⁸ O used for the second exposure. The oxide layer, formed in these conditions was studied by SEM and TEM and could be divided in two parts: an external discontinuous layer composed of crystallites rich in iron and an internal continuous layer richer in chromium. Tracer experiments revealed that the growth of this protective scale was due to oxygen diffusion in the grain boundary of the oxide layer. Defects created by irradiation have an effect on the two oxide layers. They are a preferential nucleation site for the external layer and so increase the density of the crystallites. They also induce a slower diffusion of oxygen in the internal layer.     

Predictions and Analyses on the Growth Behavior of Oxide Scales Formed on Ferritic–Martensitic in Supercritical Water

Oxidation of Metals - For 9–12Cr ferritic–martensitic steels in supercritical water, the dependencies of the thicknesses of three oxide layers (diffusion, inner, and outer layers) on...     

Effect of Annealing Ambience on the Chemical Stability of Zr-Si-N Diffusion Barrier

Cu has been drawn much attention as a newinterconnect material in ULSI due to its low resistivity,high resistance to electromigration and stress migration[1].However,Cu can easily diffuse into Si wafer evenat temperature below200°C,which degrades thereliability of the devices.It is well recognized that adiffusion barrier between Cu and Si is necessary toprevent the diffusion.Diffusion barriers are usuallychosen among refractory metals and their nitrides suchas Ta,TiN,TaN,and ZrN[2,5].R…     

Dynamics of the Oxygen Adsorption Process on the Surface of Aluminum–Cerium Alloy in Polycrystalline and Amorphous States

Protection of Metals and Physical Chemistry of Surfaces - Based on the concept of collective vibrations of ions in the bulk of metal systems, the frequency of vibrations of an oxygen molecule on...     

High Temperature Tribological Properties of Ti-GLC Films Deposited on Different Bearing Steel SubstratesEI北大核心CSCD

针对航空发动机主轴轴承服役工况恶劣和类石墨碳基薄膜在高温环境下的性能研究不足等问题,采用磁控溅射技术在不同轴承钢基体(M50 钢、M50NiL 钢和 W9Cr4V2Mo 钢)上沉积 Ti-GLC 薄膜,探究在不同温度下的摩擦学性能。采用 SEM、 Raman 分析薄膜的微观结构,采用纳米压痕仪、划痕仪等测试其力学性能,利用 MFT-5000 型多功能摩擦磨损试验机测试所镀薄膜在不同温度下(室温、200 ℃、250 ℃和 300 ℃)的摩擦学性能。结果表明：在三种不同轴承钢基体沉积的 Ti-GLC 薄膜,其硬度和弹性模量变化不大,结合力从大到小依次为 M50＞M50NiL＞W9Cr4V2Mo。随着温度的升高,三种钢基体沉积 Ti-GLC 薄膜的摩擦因数均逐渐增大,而磨损率则先减小后增大,且表现出不同的磨损形式。三种轴承钢基体沉积 Ti-GLC 薄膜的最佳工作温度区间为室温~200 ℃,M50 钢基体所镀薄膜具有更好的力学性能和摩擦学性能,其结合力达到 80 N 以上, 300 ℃时的平均摩擦因数为 0.125,磨损率仅为 3.05×10^?17 m³ /(N·m)。研究成果为类石墨碳基薄膜在高温环境下的实际应用奠定了理论基础。     

Study on the serialization and applications of low carbon ductile iron

1 Introduction Ductile cast iron can be got after the molten iron in either eutectic or hypereutectic compositions modified by RE-Mg alloy or treated by enough inoculation and heat treatment, since the birth of ductile cast iron. During the development of ordinary ductile cast iron, the content of carbon is never lower than 2.0%, the low carbon ductile iron that is not treated by heat treatment and mod- ified by the inoculation alloy mainly composed of anti- spherical surface active elements …     

Influence of Metal Additives on the Electrical Conductivities of the Oxide Ceramics as an Electrode Material

The electrical conductivities are reported for various oxide ceramics and cermets at 1000°C.Adding metalcan greatly enhance the electrical condnctivities of the oxide materials.The conductivity of the ceramic addedwith metal depends on:(1)the conductivity σ_o of the oxides;(2)the content of metal additives;(3)thedispersion of the metal phase among oxide phase.The conductivity of the metal added does not affect the con-ductivity of the metal-containing ceramic.Although the metal-containing ceramic has much higher conductivi-ty than oxide ceramic,the change rate of their conductivities with temperature is similar and is controlled byE_g of the oxide.     

The inhibition of the corrosion of iron in the pH range 6–9

Abstract

Previously it was shown that upon immersion the air-formed film on iron broke down by a two-stage process, the first step being the cathodic reduction of ferric ions to ferrous. This breakdown was retarded by dissolved oxygen.

It has now been found that inhibitive ions in neutral solution stimulate the oxidation of ferrous ions by dissolved oxygen and thereby impede the first step in the breakdown process.