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71.
An alloy of Fe-10Cr-13P-7C was thermally sprayed by three different processes: (1) 80 kW low-pressure plasma spraying (LPPS),
(2) high-velocity oxyfuel (HVOF) spraying, and (3) 250 kW high-energy plasma spraying (HPS). The as-sprayed coating obtained
by the LPPS process was composed of an amorphous phase. In contrast, the as-sprayed coatings obtained by the HVOF and HPS
processes were a mixture of amorphous and crystalline phases. The as-sprayed coatings showed a high hardness of 700 DPN. A
very fine structure composed of ferrite, carbide, and phosphide was formed, producing a maximum hardness of greater than 1000
DPN in the LPPS coating just after crystallization on tempering. The corrosion re-sistance of the amorphous coating was superior
to a SUS316L stainless steel coating in 1N H2SO4 solution and 1N HC1 solution. Furthermore, the amorphous coating underwent neither general nor pitting corro sion in1NUCI solution and 6% FeCl3 6H2O solution containing 0.05N HCl, whereas the SUS316L stain less steel coating was attacked aggressively. 相似文献
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Yang Gao Lian-Tong An Cheng-Qi Sun Zhi-Jun Yan 《Journal of Thermal Spray Technology》2004,13(4):521-525
The effects of the composition of plasma gases (Ar-N2, Ar-H2), arc current, and voltage on the temperature and velocity of a low-power (5 kW) plasma torch in the arc field free region
has been investigated using an enthalpy probe. Coatings of Al2O3-13TiO2 were deposited under different conditions. The results show that in the Ar-N2 plasma, the enthalpy, temperature, and velocity change little with arc current and voltage when regulating the nitrogen proportion
in the plasma gas. The hardness of the resulting coatings is 800 to 900 kg/mm2 HV.300. For Ar-H2 plasma, however, increases in the H2 content in the mixture of the gases remarkably enhanced the velocity and heat transfer ability of the plasma jet, with the
result that the coatings showed high hardness up to 1200 HV. 相似文献
76.
采用大气等离子喷涂在低碳钢基底上制备了含有89.2%非晶的NiCrBSi涂层。应用X射线衍射分析和Weibull分布研究了两个晶化温度523℃和628℃下热处理2~6h对涂层微观结构和显维硬度的影响。结果表明,在两个温度下,晶化析出相晶粒大小和涂层的显微硬度Weibull模数都随着热处理时间的延长而增大,涂层均匀性变好。在523℃热处理,随着热处理时间延长,涂层显微硬度增大,在4h时达到最大值,而后下降;628℃热处理,显微硬度在2h时达最大值,而后随热处理时间延长而下降。523℃热处理4h,涂层具有最高显微硬度。 相似文献
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Tribological properties of TiC-Fe coatings obtained by plasma spraying reactive powders 总被引:1,自引:0,他引:1
Titanium carbide-based coatings have been considered for use in sliding wear resistance applications. Carbides embedded in
a metal matrix would improve wear properties, providing a noncontinuous ceramic surface. TiC-Fe coatings obtained by plasma
spraying of spray-dried TiC-Fe composite powders containing large and angular TiC particles are not expected to be as resistant
as those containing TiC particles formed upon spraying. Coatings containing 60 vol% TiC dispersed in a steel matrix deposited
by plasma spraying reactive micropellets, sintered reactive micropellets, and spray-dried TiC-Fe composite powders are compared.
The sliding wear resistance of these coatings against steel was measured following the test procedure recommended by the Versailles
Advanced Materials and Standards (VAMAS) program, and the inherent surface porosity was evaluated by image analysis. Results
show that, after a 1-km sliding distance, TiC-Fe coatings obtained after spraying sintered reactive powders exhibit scar ring
three times less deep than sprayed coatings using spray-dried TiC-Fe composite powders. For all coatings considered, porosity
is detrimental to wear performance, because it generally lowers the coating strength and provides cavities that favor the
adhesion of metal. However, porosity can have a beneficial effect by entrapping debris, thus reducing friction. The good wear
behavior of TiC-Fe coatings manufactured by plasma spraying of sintered reactive powders is related to their low coefficient
of friction against steel. This is due to the microstructure of these coatings, which consists of 0.3 to 1 μm TiC rounded
particles embedded in a steel matrix.
Presented at the International Conference on Metallurgical Coatings and Thin Films, ICMCTF-92, Apr 6–10, 1992, San Diego. 相似文献
80.
Zircon, ZrSiO4, is a natural mineral used for various applications as a refractory bulk material. It is an excellent feedstock for the plasma
spraying of protective coatings and free-standing bodies. Zircon decomposes on spraying into t-ZrO2 and glassy SiO2, which can be preserved in deposits by fast cooling. This combination of zirconia and silica exhibits properties such as
a high thermal shock resistance, good corrosion resistance, low wettability, etc. The final properties of deposits can be
further enhanced by the addition of other materials such as alumina. For instance, alumina-zircon plasma-sprayed free-standing
pipes have a low gas permeability. Several technical applications are discussed. 相似文献