Cui Haotian,Yang Rongqian,Cui Gongjun,Li Xun,Li Junxia,Kou Ziming
This research aims to design a high-temperature wear resistance cobalt-based coating of hot-end parts as protective coating. The cobalt-based matrix coatings were reinforced by NiCrAlY and different contents of TiC (6.0, 8.0 and 10.0 wt%) using laser cladding technology. Some efforts were made to explore the influence of TiC on the microstructure, hardness and wear behavior of prepared coatings. The wear behavior of coatings was done via a ball-on-disk wear machine under room temperature -800 °C. The results showed that NiCrAlY decomposed and formed γ-Co(fcc) and β-NiAl phases. The hardness of coatings with TiC was reinforced due to the fine-grain strengthening and dispersion strengthening. The friction coefficients of reinforced coatings were destroyed due to the TiC particle and in-situ synthetized ceramic particles, whereas the wear resistance of coatings with TiC was enhanced. There existed an optimal content of TiC for the wear resistance of Co-NiCrAlY-TiC coatings. The coating with 8.0 wt% TiC had a satisfactory tribologcial performance at test temperatures. It was ascribed to the moderate hardness and in-situ synthetized solid lubricants, as well as the tribo-layer.
Dongqing Guo,Junhong Jia,Zongyu Zhang,Jie Yang,Jian Wang,Xiaoyu Jiao,Yun Shi,Leping Cai,Nairu He
In effort to reveal the high-temperature lubrication mechanisms of ternary oxides containing Mo/Co/Ni, the tribological characteristics of atmospheric plasma sprayed (APS) NiCrAlY-MoO 3 /CoO composite coatings at elevated temperatures were investigated. The high-temperature lubrication mechanisms of Co/Ni-molybdate formed on worn surfaces were analyzed through experimental analysis and density functional theory (DFT) calculations. The results demonstrate that the coefficient of friction (COF) of NiCrAlY coating after 30 % MoO 3 /CoO added decreased from 0.43 to 0.30 and the wear rate reduced from 5.00 × 10 −5 to 8.32 × 10 −6 mm 3 N −1 m −1 at 800 °C. This is ascribed to the synergistic lubrication effects of the layer crystal structured ternary oxides CoMoO 4 and NiMoO 4 , which are self-generated through tribo-chemical reactions on the worn surface at elevated temperatures. DFT calculations show that the binding energies of Co O (−1.05 eV) and Ni O (−0.61 eV) in the detected ternary oxides CoMoO 4 and NiMoO 4 are weaker than those of the corresponding bonds in binary oxides CoO (−1.99 eV) and NiO (−1.44 eV), and have potential to break more easily at high temperatures. Such layered structures with easy-to-break bonds of the ternary oxides containing Mo/Co/Ni provides excellent lubrication properties in the composite coatings.
Qingqing Zhang,Junhong Jia,Runze Wei,Xiaoyu Jiao,Nairu He,Jie Yang,Haichao Zhao,Dongshen Li
NiCrAlY-based composite coatings with 10–30 wt% MoO 3 -Bi 2 O 3 (1:1) were fabricated by atmospheric plasma spraying (APS) for high-temperature self-lubrication. Their tribological behaviors against GH5188 superalloy were evaluated from room temperature (RT) to 800 ℃. While both porosity and microhardness increased with oxide content, the 20 wt% coating (NMB2) exhibited optimal overall performance, achieving a minimum friction coefficient of 0.28 and a wear rate of 2.84 × 10 −5 mm 3 /(N·m) at 800 ℃. At elevated temperatures, lubricating oxides such as NiMoO 4 and CoMoO 4 formed on the wear surface. Concurrently, Co and W from the GH5188 counterpart oxidized and transferred, contributing to a stable composite tribofilm. This synergistic film effectively reduced friction and wear, identifying the NMB2 as a promising protective solution for high-temperature reciprocating components in aerospace applications.
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