Acta Chimica Sinica
Passive film formed on 304 stainless steel in 2.5 mol/L H2SO4 solution by using alternating voltage (A. V.) passivation have been investigated by measuring capacitance and photoelectrochemical parameters. The investigation of the effect of measure frequency on the slope of Mott-Schottky curve has been carried out. The photoelectrochemical measurements were consistent with the capacitance measurement. Analysis of the experimental results showed that the passive film formed 304 stainless steel by using A. V. passivation exhibits semiconducting properties. Using the simple model of semiconductor rather than the multi-donor level model can explain satisfactorily the semiconducting behavior of the film formed on 304 stainless steel by using A.V. passivation.
关键词:
A. V. passivation;passive film;semiconducting properties;stainless;steel;model;electrodes
材料科学技术（英文）
A study was conducted to develop low-friction,wear-resistant surfaces on high temperature alloys for the temperature range from 26 degrees C to 900 degrees C. The approach investigated consists of modifying the naturally occurring oxide film in order to improve its tribological properties. improvement is needed at low temperatures where the oxide film, previously formed at high temperature, spalls due to stresses induced by sliding. Experiments with Ti, W and Ta additions show a beneficial effect when added to Ni and Ni-base alloys. Low friction can be maintained down to 100 degrees C from 900 degrees C. For unalloyed Ni friction and surface damage increases at 400 degrees C to 500 degrees C. Two new alloys were perpared based on the beneficial results of binary alloys and ZrO2 diffusion in Ni. Low friction at temperature above 500 degrees C and reasonable values (0.32 similar to 0.42) at low temperature are obtained.
关键词:
oxidation;behavior;alloys
Surface & Coatings Technology
The discontinuous and cyclic oxidation behavior of TiAlNb intermetallics with coatings such as NiCrAlY, TiAlCr and ultrafine enamel coatings at 800 C was studied. The results indicated that the three coatings could decrease the mass gains of TiAlNb alloys during discontinuous and cyclic oxidation at 800 C. However, heavy interdiffusion occurred at the interface of NiCrAIY/TiAlNb during oxidation. Some discontinuous Al2O3 scales formed at interface of NiCrAIY/TiAlNb, where interdiffusion might be depressed. A protective Al2O3 scale could form on TiAlCr coating during oxidation at 800 C; however, the outward diffusion of Nb and inward diffusion of Cr through the interface and the formation of Al-depletion zone at the subsurface might be detrimental to the long-term oxidation resistance of coating. Enamel coating kept intact during oxidation at 800 C. But the thermodynamic instability of enamel in contact with TiAl alloys resulted in the formation of an Al-depletion zone and TiSiO3 layer at the interface of enamel/TiAlNb, which would be harmful to the adherence of the enamel coating to the substrate. (c) 2004 Published by Elsevier B.V.
关键词:
TiAlNb intermetallics;discontinuous and cyclic oxidation;coatings;tial-based intermetallics;high-temperature air;titanium aluminides;nb;addition;ti60 alloy;resistance;corrosion
S.Q. Zhou
,
W. Zhao
,
W.H. Xiong
,
Y.N. Zhou
,
null
,
null
,
null
,
null
金属学报(英文版)
Effect of Mo and Mo2C on the microstructure
and properties of Ti(C,N)-based cermets was investigated in this
article. The results have indicated that the weight percentage of Mo
from 5 to 10 can reduce Ti(C,N) grain diameter and thickness of the
rim, and Ti(C,N) grain can be wetted by Ni-Cu-Mo liquid so as to get
small contiguity of Ti(C,N) grain. In that way, the transverse
rupture strength of Ti(C,N)-based cermets has reached
1800—1900 MPa; the fracture toughness has been due to
16—18 MPa m1/2. But 15wt pct Mo was not more effective
on Ti(C,N)-based cermets, because the thickness of the rim becomes
larger. In the circumstance of Mo 2 C, 5 wt pct Mo 2 C was
good for microstructure and properties of Ti(C,N)-based cermets, but
11 wt pct Mo 2 C has resulted in larger contiguity of Ti(C,N)
grain and big Ti(C,N) grain diameter so as to reduce transverse
rupture strength and fracture toughness. So that, the effect of Mo
on Ti(C,N)-based cermets is better than Mo 2 C.
关键词:
Transverse rupture strength (TRS)
,
null
,
null
Fatigue & Fracture of Engineering Materials & Structures
Fatigue data for welded joints subjected to an explosion treatment (ET) were obtained using rotary bending fatigue specimens. The fatigue fracture surfaces were observed by SEM and the dislocation morphologies by TEM. Mechanical properties have been quantitively studied by considering elastic and plastic shock wave characteristics. The test results indicate that the fatigue strength of welded joints subjected to ET is apparently improved due to the action of elastic or plastic stress waves while the ductility of the welded joints, i.e., reduction in area, is greatly increased.
关键词:
Journal of Materials Processing Technology
The effects of brazing temperature on microstructure and bonding strength of vacuum brazed joints of Ti(C,N)-based cermet and 17-4 PH stainless steel, using filler metal BNi-2, were investigated. At a lower brazing temperature of 1050 C. the distribution of melting point depressants (MPD) concentrated on the diffusion affected zone (DAZ) and the brazing seam near the Ti(C,N)-based cermet, the generation of brittle phases in the brazing seam was unavoidable. The uniform distribution of the MPD and full solid solution of gamma-nickel occurred in the brazing seam at a higher brazing temperature of 1150 degrees C. A maximum shear strength of 690 MPa was achieved at a brazing temperature of 1150 degrees C. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Brazing;Ti(C,N)-based cermet;Steel;Microstructure;Mechanical;properties;isothermal solidification
Materials Science and Technology
The relationship between degeneration of the primary M7C3 carbide and precipitation of the secondary M23C6 carbide has been investigated in a cobalt base superalloy after 100 h aging at 850 degrees C. The results indicated that the primary M7C3 carbide could not transform in situ into the secondary M23C6 carbide. The M23C6 formed by a direct reaction between chromium and carbon atoms. The dissolution of M7C3 provided the precipitation of M23C6 with essential carbon, which acted as a carbon reservoir. Near M7C3, the chromium content is a controlling factor of M23C6 precipitation while away from it, the carbon content dominated the reaction. The precipitate free zone around M7C3 is attributed to chromium depletion which is inherited from the as cast condition. MST/4174
关键词:
张明星
,
材料热处理学报
doi:10.3969/j.issn.1009-6264.2000.02.009
用菊池衍射测定相间位向关系新技术对一种白口铸铁中M7C3型碳化物的晶体学进行了研究.结果表明,在这一材料中至少M7C3型碳化物属于正交晶系,而非一般认为的六方晶系.发现了三种M7C3型碳化物与奥氏体间的位向关系.它们是:(15)C∥(111)A,[101]C∥[10]A和(11)C∥(1)A,[01]C∥[0]A以及(21)C∥(11)A,[112]C∥[0]A.应用最近提出的"Edge-to-edge" Matching理论可对这一结果作出合理的解释.
关键词:
菊池衍射
,
M7C3型碳化物
,
位向关系
