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

Nanotechnology Coatings for Erosion Protection of Turbine Components

[+] Author and Article Information
V. P.“Swami” Swaminathan

 TurboMet International, San Antonio, TX 78250

Ronghua Wei

 Southwest Research Institute, San Antonio, TX 78238

David W. Gandy

 Electric Power Research Institute, Charlotte, NC 28262

J. Eng. Gas Turbines Power 132(8), 082104 (May 18, 2010) (8 pages) doi:10.1115/1.3028567 History: Received May 17, 2008; Revised September 10, 2008; Published May 18, 2010

Solid particle erosion (SPE) and liquid droplet erosion (LDE) cause severe damage to turbine components and lead to premature failures, business loss, and repair costs to power plant owners and operators. Under a program funded by the Electric Power Research Institute, TurboMet International and Southwest Research Institute (SRI) have developed hard erosion resistant nanocoatings and have conducted evaluation tests. These coatings are targeted for application in steam and gas turbines to mitigate the adverse effects of SPE and LDE on rotating blades and stationary vanes. Based on a thorough study of the available information, the most promising coatings, such as nanostructured titanium silicon carbonitride (TiSiCN), titanium nitride (TiN), and multilayered nanocoatings, were selected. State-of-the-art nanotechnology coating facilities at SwRI were used to develop the coatings. The plasma enhanced magnetron sputtering method was used to apply these coatings on various substrates. Ti–6Al–4V, 12Cr, 17-4PH, and custom 450 stainless steel substrates were selected based on the current alloys used in gas turbine compressors and steam turbine blades and vanes. Coatings with up to 30μm thickness have been deposited on small test coupons. Initial screening tests on coated coupons by solid particle erosion testing indicate that these coatings have excellent erosion resistance by a factor of 20 over the bare substrate. Properties of the coating, such as modulus, hardness, microstructural conditions including the interface, and bond strength, were determined. Tensile and high-cycle fatigue tests on coated and uncoated specimens indicate that the presence of the coatings has no negative effects but has a positive influence on the high-cycle fatigue strength at zero and high mean stresses.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Examples of SPE and LDE damage to combustion and steam turbine components

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Figure 2

Plasma enhanced magnetron sputtering system with two magnetrons

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Figure 3

Topological (left) and cross-sectional (right) images of stellite coating deposited on the 17-4 PH substrate; SEM secondary electron images. (a) With no nitrogen (straight stellite) and (b) multilayer coating with and without nitrogen (multilayer is visible in the optical microscope photo at bottom).

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Figure 4

Example of a coated and tested disk specimen (top) and erosion test results at the 30deg incident angle. STLT0-30 is the substrate 17-4PH with no coating. Stellite 30 is the sample prepared from the Stellite 6 plate stock. Results from 90deg tests are similar.

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Figure 5

Microstructural quality of TiSiCN coating on two substrates at different coating deposition process variables. Rank 1 is the best structure.

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Figure 6

Example of coating adhesion strength assessment of TiSiCN nanocomposite coatings on Ti alloy substrate using Rc Hardness indentations. The coating thickness is ∼10μm on these three samples.

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Figure 7

Example of scratch test data for quantitative measurement of the adhesion strength of the coating on C-450 substrate, monolithic TiSiCN. Top: traces of the various parameters recorded during the scratch test (Sample C3G). Bottom: scratch (about 3mm long) on a sample coated with TiSiCN nanocomposite. Lc1 (64N) shows the start of coating cracking and at Lc2 (106N) delamination and spallation.

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Figure 8

Solid particle erosion (SPE rate comparison of Ti–6Al–4V and 17-4PH samples coated with TiSiCN coating using various processing parameters. Better coatings are toward the right side of the plot with lower erosion rates. The 3 best coatings are TDOE 12, 13, and 18.

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Figure 9

Erosive mass loss as a function if incident angle for ductile (Al) and brittle (aluminum oxide) materials showing typical “ductile” and “brittle” responses to solid particle erosion. Note the variation in the magnitude of erosion in the Y axis label.

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Figure 10

SEM images of surface morphology (left) and cross section (right) of a multilayered TiSiCN coating

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Figure 11

SEM images of surface morphology (left) and cross section (right) of a multilayered TiN coating

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Figure 12

Rockwell C hardness indentations on four coatings on custom 450 stainless steel substrate showing good adhesion (Rank 1)

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Figure 13

Solid particle erosion test results on single and multilayer coatings produced under different processing conditions showing significant erosion resistance. Single layer coatings are better than the multilayer coatings under SPE.

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Figure 14

Comparison of erosion rates of commercial TiN coating by CAPVD and the advanced nano-composite coatings by PEMS




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