The Heat and Diffusion Treatment of Natural and Synthetic Sapphires

1981 ◽  
Vol 17 (8) ◽  
pp. 528-541 ◽  
Author(s):  
Robert Crowningshield ◽  
Kurt Nassau
Keyword(s):  
Diffusion Treatment ◽  
And Diffusion ◽  
Natural And Synthetic

Research on Thermal Spray Al-Al2O3/TiO2 Coating and Diffusion Treatment on Magnesium Alloy

2006 ◽  
Vol 532-533 ◽  
pp. 217-220
Author(s):  
Hong Ye ◽  
Zhong Lin Yan ◽  
Zhi Fu Sun ◽  
Ying Wang
Keyword(s):  
Magnesium Alloy ◽  
Thermal Shock ◽  
High Hardness ◽  
Flame Spray ◽  
Diffusion Treatment ◽  
Az91d Magnesium Alloy ◽  
Spray Method ◽  
Shock Resistance ◽  
And Diffusion ◽  
Electronic Microscope

Flame spray method was used to prepare the Al-Al2O3/TiO2 gradient coating on AZ91D magnesium alloy surface, where diffusion treatment for 2 hours at 380～420 °C was needed to reinforce the binding strength between the coating and the substrate. Appearance and compositions of the coating were analyzed by scanning electronic microscope (SEM) and electron probe microanalysis (EPMA), and the thermal shock resistance and wear resistance of the coating were tested. The result shows: Al-Mg diffusion is produced between the coating and the substrate, for good metallurgy; coating acquires high hardness and resistant to wear and thermal shock.

EFFECT OF DIFFUSION PROCESS ON COATING IN HOT-DIPPED ALUMINIZED STEEL

2019 ◽  
Vol 26 (10) ◽  
pp. 1950070
Author(s):  
YUWEN DING ◽  
XIAOCHUN CHEN ◽  
YA LIU ◽  
XUPING SU
Keyword(s):  
Corrosion Resistance ◽  
Diffusion Process ◽  
Diffusion Path ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intermetallic Coating ◽  
Diffusion Treatment ◽  
Aluminized Steel ◽  
And Diffusion

Aluminized steels possess excellent corrosion resistance due to the formation of Al-Fe solution phases and intermetallic compounds in coatings. Ni was added to baths to further improve the corrosion resistance of the coatings at high temperature. Here, the role of Ni in the formation of coatings and the effect of diffusion process on the developing of coatings were investigated. 45 steels were immersed in Al-Ni baths (Al-1mass% Ni, Al-3mass% Ni, and Al-5mass% Ni) and diffusion-treated at 1023 and 1123[Formula: see text]K for 20, 40 and 100[Formula: see text]min, respectively. The coatings of samples were analyzed via scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy (EDS). X-ray diffraction (XRD) was further used to confirm the types of phases that formed during diffusion treatment. The formations of intermetallic coating layers were also analyzed via the diffusion path. More continuous Al3Ni layer and compact coating were obtained with diffusion treatment at 1023[Formula: see text]K for 40[Formula: see text]min.

Oxidation Resistance of Al-Rich Aluminide Coating on TiAl Based Alloy by Thermal Spray and Diffusion Treatment

2011 ◽  
Vol 409 ◽  
pp. 820-825 ◽  
Author(s):  
Takahiro Yagi ◽  
Tomohiro Sasaki ◽  
Takehiko Watanabe ◽  
Atsushi Yanagisawa
Keyword(s):  
Oxidation Resistance ◽  
Intermediate Layer ◽  
Aluminide Coating ◽  
Al Alloys ◽  
Diffusion Time ◽  
Oxide Scales ◽  
Oxidation Test ◽  
Diffusion Treatment ◽  
Lower Oxidation ◽  
And Diffusion

Al-rich aluminide coating on Ti-49.1at%Al alloys has been performed by two-step process of thermal aluminum spray and diffusion treatment. Effect of the diffusion time on the oxidation resistance, and the change of microstructures in the coating during the oxidation test in air at 900°C for 100 h were investigated. In the aluminized coating before the oxidation tests, formations of TiAl3 on the outer layer and an intermediate layer consisting of Ti2Al5, TiAl2, and Al-rich TiAl were observed. The intermediate layer developed by the diffusion treatment for 3600s. In the oxidation test over 50 h, the specimen diffusion treated for 3600 s exhibited the lower oxidation rate than that diffusion treated for 900 s. Multi-oxide scales of TiO2 and Al2O3 were observed on the both surfaces of aluminized specimens. Large TiO2 particles were observed on the specimen of tD = 900 s. It was found that the TiAl2 layer developed during the oxidized specimen, while the thicknesses of Al-rich TiAl and TiAl3 layer decreased by the growth of TiAl2.

Optimization of Process Parameters of Hot-Dip Aluminized Coating

2011 ◽  
Vol 391-392 ◽  
pp. 46-50 ◽  
Author(s):  
Jiang Chen ◽  
Guang Ze Dai ◽  
Jun Wen Zhao ◽  
Xing Min Huang ◽  
Jing Han
Keyword(s):  
Process Parameters ◽  
Treatment Time ◽  
Uniform Design ◽  
Treatment Temperature ◽  
Polynomial Equations ◽  
Third Order ◽  
Diffusion Treatment ◽  
Optimization Of Process Parameters ◽  
Order Polynomial ◽  
And Diffusion

The hot-dip aluminized process parameters with respect to the thickness and microstructure of intermetalic layer were investigated using a uniform design of experiments. The measured thickness of intermetalic layer was regressed as first- to third-order polynomial equations of four related parameters, i.e. hot-dip temperature, hot-dip time, diffusion treatment temperature and diffusion treatment time. It was found that the third-order regressed equation was acceptable and appropriate to identify the influences of the investigated parameters on the thickness of intermetalic layer. Comprehensive analysis of the results based on the regressed equation and microstructure could supply believable and optimized process parameters.

An Eshelbian homogenization solution for a coupled stress-diffusion moving interface problem in composites

2016 ◽  
Vol 01 (03n04) ◽  
pp. 1640011 ◽  
Author(s):  
Yang Zhang ◽  
Xian-Cheng Zhang ◽  
Shan-Tung Tu ◽  
Shaofan Li
Keyword(s):  
Diffusion Process ◽  
Chemical Potential ◽  
Diffusion Processes ◽  
Homogenization Method ◽  
Interface Problem ◽  
Diffusion Treatment ◽  
Moving Interface ◽  
Normal Diffusion ◽  
The One ◽  
And Diffusion

In this work, we proposed a homogenization model to treat the coupled mechanical-diffusion moving interface problem. The Eshelbian homogenization method is applied to find the effective mechanical properties and diffusivity. On the one hand, the diffusion of solute elements would induce the formation of inclusion phases, affecting the mechanical equilibrium, properties and diffusivity. On the other hand, the stress condition will also have effects on the chemical potential and diffusion process. The coupling of the mechanical and diffusion processes were simulated using the present model, i.e., normal diffusion process and that with previous diffusion treatment. In the former case, thicknesses of outer and inner diffusion parts both increased with time. In the latter case, decomposition of the outer diffusion part might take place to maintain the growth of the inner part.

Interdiffusion between Ni Based Superalloy and Diffusion Barrier Coatings at 1423K

2006 ◽  
Vol 522-523 ◽  
pp. 285-292 ◽  
Author(s):  
Hiroyuki Matsumaru ◽  
Shigenari Hayashi ◽  
Toshio Narita
Keyword(s):  
Diffusion Couple ◽  
Single Crystal ◽  
Diffusion Barrier ◽  
Alloy Layer ◽  
Quartz Ampoule ◽  
Diffusion Couples ◽  
Outward Diffusion ◽  
Barrier Coatings ◽  
Diffusion Treatment ◽  
And Diffusion

A diffusion couple study was carried out with Ni-based superalloy / γ’-Ni3Al with or without a Re-based alloy layer. The Re-based alloy containing Re, W, Cr, and Ni was formed on a second generation, single crystal Ni-based superalloy by using electroplating processes to form films of 70at%Re-Ni and Ni-20at%W, followed by Cr-pack cementation at 1573K for 36ks. The superalloy with or without the Re-based alloy layer was bonded to a γ’−Ni3Al alloy in vacuum. Diffusion couples were annealed in an evacuated quartz ampoule at 1423 K for 90 and 360ks. After the 360ks diffusion treatment the Re-based alloy remained sound and suppressed inward Al diffusion from the γ’-Ni3Al, it was further found that outward diffusion of alloying elements from the alloy substrate to the γ’-Ni3Al was also significantly reduced by the Re-based alloy layer.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

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