Microstructural Characterization, Mechanical Properties and Wear Resistance of TiCP Reinforced Ni-Alloy Coatings by Laser Synthesis

2000 ◽  
Author(s):  
D. L. Tu ◽  
A. Kar ◽  
X. L. Wu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Wear Resistance ◽  
Chemical Reaction ◽  
Phase Interface ◽  
High Fracture Toughness ◽  
Transmission Electron ◽  
Ni Alloy ◽  
The Matrix

Abstract Titanium carbide particle (TiCp)-reinforced Ni alloy composite coatings are synthesized by laser cladding using a cw 3 kW CO2 laser. Two kinds of coatings are possible in terms of the origin of TiCp: undissolved TiCp and in-situ generated TiCp. The former originates from the TiCp pre-coated on the sample whereas the latter from in-situ chemical reaction between titanium and graphite in the molten pool during laser irradiation. For the coating reinforced by TiCp formed in-situ, the sub-micron TiCp particles are formed and uniformly distributed because of the in-situ reaction and trapping effect during rapid solidification. Graded distribution of TiCp is obtained on a macro scale. The volume fraction increases from 1.86% at the coating-substrate interface to 38.4% at the coating surface. For the coating reinforced by undissolved TiCp, analytical transmission electron microscopy (ATEM) and high resolution transmission electron microscopy (HRTEM) observations show the existence of the epitaxial growth of TiC, the precipitation of CrB and M23C6, and the chemical reaction between Ti and B elements around phase interfaces of undissolved TiCp. In the matrix near the phase interface of undissolved TiCp, the loading curve obtained by nanoindenter exhibits pop-in phenomena due to the plastic deformation of cracks or debonding of TiCp from the matrix. For TiCp generated in-situ, no pop-in mark appears, indicating high fracture toughness. Coating with TiCp generated in-situ exhibits higher hardness and modulus than the coating with undissolved TiCp at regions near the phase interface. The coating reinforced by TiCp generated in-situ also displays higher impact wear resistance and abrasive wear resistance compared to the coatings with undissolved TiCp and without TiCp respectively.

In Situ TEM Heating Study of the γ Lamellae Formation inside the α2 Matrix of a Ti-45Al-7.5Nb Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 1365-1368 ◽  
Author(s):  
Li Mei Cha ◽  
Helmut Clemens ◽  
Gerhard Dehm ◽  
Zao Li Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ex Situ ◽  
In Situ Tem ◽  
Transmission Electron ◽  
Initial Stage ◽  
Heat Treated ◽  
The Matrix ◽  
In Situ Heating

In-situ heating transmission electron microscopy (TEM) was employed to investigate the initial stage of lamellae formation in a high Nb containing γ-TiAl based alloy. A Ti-45Al-7.5Nb alloy (at %), which was heat treated and quenched in a non-equilibrium state such that the matrix consists of ordered a2 grains, was annealed inside a TEM up to 750 °C. The in-situ TEM study reveals that g laths precipitate in the a2 matrix at ~ 750 °C possessing the classical Blackburn orientation relationship, i.e. (0001)a2 // (111)g and [11-20]a2 // <110]g. The microstructure of the in-situ TEM experiment is compared to results from ex-situ heating and subsequent TEM studies.

Nano-Crystalline Structure in Mg2Si/Mg-2.5Er-5Zn Composite on the Route of Repeated Plastic Working Process

2010 ◽  
Vol 667-669 ◽  
pp. 635-639
Author(s):  
Wen Bo Du ◽  
Xu Dong Wang ◽  
Zhao Hui Wang ◽  
Shu Bo Li
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Second Phase ◽  
Plastic Working ◽  
Nano Crystalline ◽  
Transmission Electron ◽  
The Matrix ◽  
Nonequilibrium Grain Boundaries ◽  
The Difference

The Mg-5Zn-2.5Er matrix composite reinforced with the in-situ synthesized Mg2Si second phase particles was fabricated via repeated plastic working (RPW) process. The microstructures and the nanocrystals in the composite have been investigated using transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HREM) and energy dispersive X-ray (EDX). Great deals of nanocrystals were found in the matrix, and they were around the in-situ synthesized Mg2Si. The HREM analysis showed that the size of nanocrystals was in the range of 5-10 nm, and the difference in their crystallographic orientation was bigger than 15°. It is suggested that the formation of nanocrystals in the matrix is attributed to the RPW deformation process and to the intensive stresse fields around the in-situ synthesized Mg2Si particles, which suppress the growth of nanocrystals by forming nonequilibrium grain boundaries containing disordered dislocation networks and junction disclinations.

Metal/ceramic interface in an in situsynthesized Ti/TiCP composite coating by laser processing

2001 ◽  
Vol 16 (1) ◽  
pp. 9-12 ◽  
Author(s):  
R. Yu ◽  
S. Zhang ◽  
L. L. He ◽  
W. T. Wu ◽  
H. Q. Ye
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Composite Coating ◽  
Laser Processing ◽  
Transmission Electron ◽  
Metal Ceramic ◽  
The Matrix ◽  
Metallic Bonding

The metal/ceramic interface in an in situ synthesized Ti/TiCP composite coating by laser processing was analyzed using high-resolution transmission electron microscopy. The TiC particles were distributed uniformly in the matrix and were highly faceted. The interfaces between the TiC particles and the β matrix were abrupt and free of any other reaction phases. It was the Ti-terminated TiC surface that bonded to the β matrix, resulting in the metallic bonding between the TiC particles and the matrix.

Epitaxy and texture analysis of Bi-Sr-Ca-Cu-O thin films on (100) MgO using Transmission Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 68-69
Author(s):  
J. T. Sizemore ◽  
D. G. Schlom ◽  
Z. J. Chen ◽  
J. N. Eckstein ◽  
I. Bozovic ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Critical Currents ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Cell Axis ◽  
Transmission Electron ◽  
Synthesis Procedure

Investigators observe large critical currents for superconducting thin films deposited epitaxially on single crystal substrates. The orientation of these films is often characterized by specifying the unit cell axis that is perpendicular to the substrate. This omits specifying the orientation of the other unit cell axes and grain boundary angles between grains of the thin film. Misorientation between grains of YBa2Cu3O7−δ decreases the critical current, even in those films that are c axis oriented. We presume that these results are similar for bismuth based superconductors and report the epitaxial orientations and textures observed in such films.Thin films of nominally Bi2Sr2CaCu2Ox were deposited on MgO using molecular beam epitaxy (MBE). These films were in situ grown (during growth oxygen was incorporated and the films were not oxygen post-annealed) and shuttering was used to encourage c axis growth. Other papers report the details of the synthesis procedure. The films were characterized using x-ray diffraction (XRD) and transmission electron microscopy (TEM).

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

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