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Effect of nano-CeO<sub>2</sub> on cobalt-based alloy laser coatings
Li, Mingxi,Zhang, Shihong,Li, Huisheng,He, Yizhu,Yoon, Jae-Hong,Cho, Tong-Yul Elsevier 2008 Journal of materials processing technology Vol. No.
<P><B>Abstract</B></P><P>Cobalt-based alloy coatings with/without nano-CeO<SUB>2</SUB> addition prepared by a 5kW CO<SUB>2</SUB> laser on Q235 low carbon steel were introduced. The effects of nanoparticles on the macro-quality, microstructure, phase composition, and wear resistance of the coatings were investigated. The microstructure and phases composition of the coatings were analyzed using Olympus-Pme-3 type microscope, Philip Xl 30 type scanning electron microscope and XD-3A type X-ray diffractometer (XRD). The wear resistance was tested using MM-200 type sliding wear machine, and the wear mechanism was analyzed by JSM-35C type scanning electron microscope (SEM). The results showed that defect (such as crack, gas hole, etc.) -free coatings were obtained. There existed γ-Co and Cr<SUB>23</SUB>C<SUB>6</SUB> in cobalt-based alloy coatings. Another two phases of CeCo<SUB>2</SUB> and ϵ-Co were identified with nanoparticles addition. Fine microstructure and equiaxed dendrite were obtained by adding nano-CeO<SUB>2</SUB>. The relative wear resistance is improved with the increased amount of nano-CeO<SUB>2</SUB>, and the coatings with the best wear resistance when laser power was 2.0kW by adding 1.5wt.% CeO<SUB>2</SUB>. The mechanism was found from abrasive/adhesive wear to fretting wear. The wear resistance decreased with 2.0wt.% CeO<SUB>2</SUB> addition.</P>
Hao Zhou,Yuhang Zuo,Yawei Li,Mingxi Zhou 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10
The thermal stress arisen from highly inhomogeneous solar radiation and temperature distribution during operation is mainly responsible for the failure of the central receiver. In the present study, the analytical approximation method, finite volume method and 2D thermoelastic analytical approach were used in combination to obtain the thermal characteristics of a 50 MWe external cylindrical receiver. The results demonstrated that the direct normal irradiance and tube surface absorptivity significantly affected the thermal stress. The axial distribution of the equivalent thermal stress at θ = 0° consisted with the surface solar flux distribution, and the maximum equivalent stress was underestimated by 30.0 % with the homogeneous surface solar flux distribution. Compared with molten salt flowing into the receiver from the south, the maximum equivalent stress and maximum wall temperature of molten salt flowing from the north are 16.3 % higher and 8.1 % lower, respectively.