Evaluation of Alternate High Temperature Coatings to Improve Hot Corrosion Resistance in a Shipboard Environment

Author(s):  
David A. Shifler ◽  
Dennis M. Russom ◽  
Bruce E. Rodman

501-K34 marine gas turbine engines serve as auxiliary power sources for the U.S. Navy’s DDG-51 Class. It is desired that 501-K34 marine gas turbine engines have a mean time between removal of 20K hours. While some engines have approached this goal, others have fallen significantly short. A primary reason for this shortfall is hot corrosion (Type I and Type II) damage in the turbine area (more specifically the first row turbine hardware) due to both intrusion of salts from the marine air and from sulfur in the gas turbine combustion fuel. The Navy’s technical community recognizes that engine corrosion problems are complex in nature and are often tied to the design of the overall system. For this reason, two working groups were formed. One group focuses on the overall ship system design and operation, including the inlet and fuel systems. The second, the corrosion issues working group, will review the design and performance of the turbine itself and develop sound, practical, economical, and executable changes to engine design that will make it more robust and durable in the shipboard operating environment. Metallographic examination of unfailed blades removed from a marine gas turbine engine with 18000 operating hours showed that the coating thickness under the platform and in the curved area of transition between the platform to the blade stem was either very thin, or in a few cases, non-existent on each unfailed blade. Type II hot corrosion was evident at these locations under the platform. It was also observed that this corrosion under the platform led to corrosion fatigue cracking of first stage turbine blades due to poor coating quality (high porosity and variable thickness). Corrosion fatigue cracks initiated at several hot corrosion sites and had advanced through the stems to varying degrees. Cracking in a few blades had advanced to the point that would have led to premature blade failure. Low velocity, atmospheric-pressure burner-rig (LVBR) tests were conducted for 1000 hours to evaluate several alternative high-temperature coatings in both Type I and Type II hot corrosion environments. The objectives of this paper are to: (1) report the results of the hot corrosion performance of alternative high temperature coating systems for under the platform of the 1st stage blade of 501-K34 gas turbine engine, (2) compare the performance of these alternative coating systems to the current baseline 1st stage blade coating, and (3) down select the best performing coating systems (in terms of their LVBR hot corrosion and thermal cycling resistance) to implement on future 501-K34 first stage blades for the Fleet.

Author(s):  
David A. Shifler ◽  
Dennis M. Russom ◽  
Bruce E. Rodman

501-K34 marine gas turbine engines serve as auxiliary power sources for the U.S. Navy’s DDG-51 Class ships. It is desired that 501-K34 marine gas turbine engines have a mean time between removal of 20K hours. While some engines have approached this goal, others have fallen significantly short. A primary reason for this shortfall is hot corrosion (Type I and Type II) damage in the hot section turbine area due to both intrusion of salts from the marine air and from sulfur in the gas turbine combustion fuels. Previous metallographic examination of several unfailed blades removed from a marine gas turbine engine after 18000 operating hours showed that the coating thickness under the platform and in the curved area of transition between the platform to the blade stem was either very thin, porous, and in a few cases, non-existent on each unfailed blade. Type II hot corrosion was evident at these locations under the platform. Corrosion fatigue cracks initiated at several hot corrosion sites and had advanced through the blade stems to varying degrees. Cracking in a few blades had advanced to the point that blade failure was imminent. The objectives of this paper are to: (1) report the hot corrosion results of alternative high temperature coating systems on Alloy M247 and Alloy 792 for hot section components of the 501-K34 gas turbine engine using a low velocity, atmospheric-pressure burner-rig (LVBR), (2) compare and rank hot corrosion performance of these coatings systems to the baseline coating/substrate system (2) down select the best performing coating systems (in terms of LVBR hot corrosion and thermal cycling resistance) to implement on future hot section components in the 501-K34 engine for the Fleet.


Author(s):  
David A. Shifler ◽  
Dennis M. Russom ◽  
Bruce E. Rodman

501-K34 marine gas turbine engines serve as auxiliary power sources for the U.S. Navy’s DDG-51 Class. It is desired that 501-K34 marine gas turbine engines have a mean time between removal of 20K hours. While some engines have approached this goal, others have fallen significantly short. A primary reason for this shortfall is hot corrosion (Type I and Type II) damage in the turbine area (more specifically the first row turbine hardware) due to both intrusion of salts from the marine air and from sulfur in the gas turbine combustion fuels. In order to improve the durability of hot section components with more corrosion resistant coatings, low velocity, atmospheric-pressure burner-rig (LVBR) tests were conducted for up to 2000 hours to evaluate several alternative high-temperature coatings in both Type I and Type II hot corrosion environments. The objectives of this paper are to report the results of: (1) the hot corrosion performance of these alternative high temperature coating systems for the 1st stage vane of a given gas turbine engine; (2) compare the performance of these alternative coating systems to the current, baseline 1st stage vane coating and (3) downselect the best performing coating systems (in terms of their LVBR hot corrosion and thermal cycling resistance) to install as rainbow arrays into the first stage vanes of several engines for Fleet evaluation.


Author(s):  
Hooshang Heshmat ◽  
James F. Walton ◽  
Brian D. Nicholson

In this paper, the authors present the results of recent developments demonstrating that ultra-high temperature compliant foil bearings are suitable for application in a wide range of high temperature turbomachinery including gas turbine engines, supercritical CO2 power turbines and automotive turbochargers as supported by test data showing operation of foil bearings at temperatures to 870°C (1600°F). This work represents the culmination of efforts begun in 1987, when the U.S. Air Force established and led the government and industry collaborative Integrated High Performance Turbine Engine Technology (IHPTET) program. The stated goal of IHPTET was to deliver twice the propulsion capability of turbine engines in existence at that time. Following IHPTET, the Versatile Affordable Advanced Turbine Engines (VAATE) program further expanded on the original goals by including both versatility and affordability as key elements in advancing turbine engine technology. Achieving the stated performance goals would require significantly more extreme operating conditions including higher temperatures, pressures and speeds, which in turn would require bearings capable of sustaining temperatures in excess of 815°C (1500°F). Similarly, demands for more efficient automotive engines and power plants are subjecting the bearings in turbochargers and turbogenerators to more severe environments. Through the IHPTET and VAATE programs, the U.S. has made considerable research investments to advancing bearing technology, including active magnetic bearings, solid and vapor phase lubricated rolling element bearings, ceramic/hybrid ceramic bearings, powder lubricated bearings and compliant foil gas bearings. Thirty years after the IHPTET component goal of developing a bearing capable of sustained operation at temperatures above 540°C and potentially as high as 815°C (1500°F) recent testing has demonstrated achievement of this goal with an advanced, ultra-high temperature compliant foilgas bearing. Achieving this goal required a combination of high temperature foil material, a unique elastic-tribo-thermal barrier coating (KOROLON 2250) and a self-adapting compliant configuration. The authors describe the experimental hardware designs and design considerations of the two differently sized test rigs used to demonstrate foil bearings operating above 815°C (1500°F). Finally, the authors present and discuss the results of testing at temperatures to 870°C (1600°F).


2013 ◽  
Vol 325-326 ◽  
pp. 1368-1373
Author(s):  
Yağız Uzunonat ◽  
Sinem Üzgür ◽  
M.C. Kushan

In this study, the basic limitations of superalloys in high temperature performances will be explained and then after giving the important properties of MoSi2such as oxidation behaviour at relatively low temperatures (500°C-700°C) , some interesting composites of this material will be discussed as a candidate structural material in gas turbine engines.


Author(s):  
P. C. Patnaik ◽  
C. Adams ◽  
D. Fuleki ◽  
R. Thamburaj

The use of biomass fuels in gas turbine engines requires an examination of the effect of the fuel on the engine materials. While the fuel may be more environmentally friendly than conventional fuels, it has the potential to produce serious life limiting corrosion within gas turbine engines. The effects of the high alkali and low sulphur content of the fuel on its corrosive properties needs to be examined. To determine the extent and type of corrosion typical material systems were exposed to bio-fuel combustion products in a flame tunnel and furnace under conditions designed to promote high temperature corrosion. The preliminary results indicate that type I hot corrosion is certainly occurring with some signs of type II hot corrosion in certain material systems.


Author(s):  
Muthuvel Murugan ◽  
Anindya Ghoshal ◽  
Michael Walock ◽  
Andy Nieto ◽  
Luis Bravo ◽  
...  

Gas turbine engines for military/commercial fixed-wing and rotary wing aircraft use thermal barrier coatings in the high-temperature sections of the engine for improved efficiency and power. The desire to further make improvements in gas turbine engine efficiency and high power-density is driving the research and development of thermal barrier coatings with the goal of improving their tolerance to fine foreign particulates that may be contained in the intake air. Both commercial and military aircraft engines often are required to operate over sandy regions such as in the middle-east nations, as well as over volcanic zones. For rotorcraft gas turbine engines, the sand ingestion is adverse during take-off, hovering near ground, and landing conditions. Although most of the rotorcraft gas turbine engines are fitted with inlet particle separators, they are not 100% efficient in filtering fine sand particles of size 75 microns or below. The presence of these fine solid particles in the working fluid medium has an adverse effect on the durability of turbine blade thermal barrier coatings and overall performance of the engine. Typical turbine blade damage includes blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicate (CMAS) attack, oxidation, and plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. The objective of this research is to understand the fine particle interactions with typical turbine blade ceramic coatings at the microstructure level. Finite-element based microstructure modeling and analysis has been performed to investigate particle-surface interactions, and restitution characteristics. Experimentally, a set of tailored thermal barrier coatings and surface treatments were down-selected through hot burner rig tests and then applied to first stage nozzle vanes of the gas generator turbine of a typical rotorcraft gas turbine engine. Laser Doppler velocity measurements were performed during hot burner rig testing to determine sand particle incoming velocities and their rebound characteristics upon impact on coated material targets. Further, engine sand ingestion tests were carried out to test the CMAS tolerance of the coated nozzle vanes. The findings from this on-going collaborative research to develop the next-gen sand tolerant coatings for turbine blades are presented in this paper.


2021 ◽  
pp. 1-11
Author(s):  
Jacob Elms ◽  
Alison Pawley ◽  
Nicholas Bojdo ◽  
Merren Jones ◽  
Rory J. Clarkson

Abstract The ingestion of multi-mineral dusts by gas turbine engines during routine operations is a significant problem for engine manufacturers because of the damage caused to engine components and their protective thermal barrier coatings. A complete understanding of the reactions forming these deposits is limited by a lack of knowledge of compositions of ingested dusts and unknown engine conditions. Past engine tests have used standardised test dusts that do not resemble the composition of the background dust in the operating regions. A new evaporite-rich test dust was developed and used in a full engine ingestion test, designed to simulate operation in regions with evaporite-rich geology, such as Doha or Dubai. Analysis of the engine deposits showed that mineral fractionation was present in the cooler, upstream sections of the engine. In the hotter, downstream sections, deposits contained new, high temperature phases formed by reaction of minerals in the test dust. The mineral assemblages in these deposits are similar to those found from previous analysis of service returns. Segregation of anhydrite from other high temperature phases in a deposit sample taken from a High Pressure Turbine blade suggests a relationship between temperature and sulfur content. This study highlights the potential for manipulating deposit chemistry to mitigate the damage caused in the downstream sections of gas turbine engines. The results of this study also suggest that the concentration of ingested dust in the inlet air may not be a significant contributing factor to deposit chemistry.


Author(s):  
Jacob Elms ◽  
Alison Pawley ◽  
Nicholas Bojdo ◽  
Merren Jones ◽  
Rory Clarkson

Abstract The ingestion of multi-mineral dusts by gas turbine engines during routine operations is a significant problem for engine manufacturers because of the damage caused to engine components and their protective thermal barrier coatings. A complete understanding of the reactions forming these deposits is limited by a lack of knowledge of compositions of ingested dusts and unknown engine conditions. Test bed engines can be dosed with dusts of known composition under controlled operating conditions, but past engine tests have used standardised test dusts that do not resemble the composition of the background dust in the operating regions. A new evaporiterich test dust was developed and used in a full engine ingestion test, designed to simulate operation in regions with evaporiterich geology, such as Doha or Dubai. Analysis of the engine deposits showed that mineral fractionation was present in the cooler, upstream sections of the engine. In the hotter, downstream sections, deposits contained new, high temperature phases formed by reaction of minerals in the test dust. The mineral assemblages in these deposits are similar to those found from previous analysis of service returns. Segregation of anhydrite from other high temperature phases in a deposit sample taken from a High Pressure Turbine blade suggests a relationship between temperature and sulfur content. This study highlights the potential for manipulating deposit chemistry to mitigate the damage caused in the downstream sections of gas turbine engines. The results of this study also suggest that the concentration of ingested dust in the inlet air may not be a significant contributing factor to deposit chemistry.


Author(s):  
Edward M. House

Four Textron Lycoming TF40B marine gas turbine engines are used to power the U.S. Navy’s Landing Craft Air Cushion (LCAC) vehicle. This is the first hovercraft of this configuration to be put in service for the Navy as a landing craft. The TF40B has experienced compressor blade pitting, carbon erosion of the first turbine blade and hot corrosion of the hot section. Many of these problems were reduced by changing the maintenance and operation of the LCAC. A Component Improvement Program (CIP) is currently investigating compressor and hot section coatings better suited for operation in a harsh marine environment. This program will also improve the performance of some engine components such as the bleed manifold and bearing seals.


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