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Research Papers: Gas Turbines: Manufacturing, Materials, and Metallurgy

# Effects of Coating Thickness, Test Temperature, and Coating Hardness on the Erosion Resistance of Steam Turbine Blades

[+] Author and Article Information
Shun-sen Wang, Guan-wei Liu, Qun-gong He, Zhen-ping Feng

Institute of Turbomachinery, Xi’an Jiaotong University, Xi’an 710049, P. R. China

Jing-ru Mao1

Institute of Turbomachinery, Xi’an Jiaotong University, Xi’an 710049, P. R. Chinajrmao@mail.xjtu.edu.cn

1

Corresponding author.

J. Eng. Gas Turbines Power 132(2), 022102 (Nov 04, 2009) (7 pages) doi:10.1115/1.3155796 History: Received February 24, 2009; Revised April 20, 2009; Published November 04, 2009; Online November 04, 2009

## Abstract

This paper experimentally examines the influence of coating thickness, test temperature, coating hardness, and defects on the erosion resistance of boride coatings, ion plating CrN coatings, and thermal spraying coatings. The results demonstrate that the erosion rate of coating can be reduced effectively by improving coating hardness and thickness with the absence of the cracks of coating during the coating process. In comparison with thermal spraying coatings, boride coatings and ion plating CrN coatings are more suitable for protecting steam turbine blades from solid particle erosion due to higher erosion resistance. However, blades cannot be protected effectively when coating is thinner than a critical value $θcrit$. Based on our results, it is recommended that the protective coating for the steam turbine blade should be thicker than 0.02 mm. In addition, the effect of temperature on erosion resistance of the coating is strongly dependent on the properties of transition layer between coating and substrate material. For the coating without pinholes or pores in the transition layer, the variation in erosion rate with temperature is consistent with that of uncoated substrate material. However, the erosion rate of coating descends with the elevation of test temperature when a lot of pinholes or pores are produced in the transition layer.

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## Figures

Figure 1

Schematic of high-temperature erosion test facility

Figure 2

Schematic of test section

Figure 3

The variation in erosion rate with α, T, and θ for boride coatings at a particle velocity of 420 m/s, θ=0.02 mm of boride coatings A and C, θ=0.06 mm of boride coatings B and D (the two figures need to be in the same scale (y-axis) so that reader can read it easily)

Figure 7

SEM micrographs of boride coatings at 420 m/s particle velocity; (a) boride coating B, α=15 deg, T=843 K; (b) boride coating B, α=75 deg, T=843 K; and (c) Boride coating D, α=75 deg, T=883 K

Figure 8

The variation of erosion rate with α for three thermal spraying coatings at a particle velocity of 420 m/s

Figure 9

SEM micrographs of thermal spraying coatings at 420 m/s particle velocity and 833 K test temperature; (a) detonation spraying Cr3C2 coating, α=90 deg; and (b) supersonic spraying WC-Co coating, α=90 deg

Figure 4

The variation in erosion rate with α, Ts and θ for ion plating CrN coatings at a particle velocity of 420 m/s, θ=0.02 mm of CrN coating A, θ=0.04 mm of CrN coating B

Figure 5

The variation of erosion rate with α for five kinds of uncoated substrate materials at a particle velocity of 420m/s

Figure 6

SEM micrographs of ion plating CrN coating at 420 m/s particle velocity and 833 K test temperature; (a) CrN coating C, α=15 deg; (b) CrN coating A, α=75 deg; and (c) CrN coating B, α=75 deg

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