scholarly journals Hot Corrosion Behaviour of Detonation Gun Sprayed Stellite-6 and Stellite-21 Coating on Boiler Steel SAE 431 at 900°C

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
N. K. Mishra ◽  
A. K. Rai ◽  
S. B. Mishra ◽  
R. Kumar
Keyword(s):  
Hot Corrosion ◽  
Gas Turbines ◽  
Elevated Temperatures ◽  
Protective Coatings ◽  
Total Duration ◽  
Boiler Steel ◽  
Stellite 6 ◽  
Stellite 21 ◽  
Wide Range ◽  
Detonation Gun

Hot corrosion is the serious problem in gas turbines, superheaters, and economizers of coal-fired boilers. It occurs due to the usage of wide range of fuels such as coal, oil, and so on at the elevated temperatures. Protective coatings on boiler steels are used under such environments. In the present investigation, Stellite-6 and Stellite-21 coatings have been deposited on boiler steel SAE 431 by detonation gun method. The hot corrosion performance of Stellite-6 and Stellite-21 coated as well as uncoated SAE 431 steel has been evaluated in aggressive environment of Na2SO4-82%Fe2(SO4)3under cyclic conditions at an elevated temperature of 900°C for total duration of 50 cycles. Thermogravimetric technique was used to approximate the kinetics of hot corrosion. Stellite-6 coating imparted better hot corrosion resistance than Stellite-21 coating in the given environment. Scanning electron microscopy was used to characterize the surface of hot corrosion products.

scholarly journals Hot Corrosion Behaviour of Detonation Gun Sprayed Al2O3-40TiO2 Coating on Nickel Based Superalloys at 900°C

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
N. K. Mishra ◽  
Naveen Kumar ◽  
S. B. Mishra
Keyword(s):  
Elevated Temperature ◽  
Hot Corrosion ◽  
Elevated Temperatures ◽  
Corrosion Behaviour ◽  
Degradation Mechanism ◽  
Total Duration ◽  
Wide Range ◽  
Detonation Gun ◽  
Mechanism Of Failure ◽  
Corrosion Resistant Coatings

Hot corrosion is the major degradation mechanism of failure of boiler and gas turbine components. These failures occur because of the usage of wide range of fuels such as, coal and oil at the elevated temperatures. Nickel based superalloys having excellent mechanical strength and creep resistance at elevated temperature are used under such environment but they lack resistance to hot corrosion at high temperature. To overcome these problems hot corrosion resistant coatings are deposited on these materials. In the current investigation Al2O3-40%TiO2 powder has been deposited on Superni 718 and AE 435 superalloys by Detonation Gun method. The hot corrosion performance of Al2O3-40%TiO2 coated as well as uncoated Superni 718 and AE 435 alloys has been evaluated in aggressive environment Na2SO4-82%Fe2(SO4)3 under cyclic conditions at an elevated temperature of 900°C. The kinetics of the corrosion is approximated by weight change measurements made after each cycle for total duration of 50 cycles. Scanning electron microscopy was used to characterize the hot corrosion products. The coated samples imparted better hot corrosion resistance than the uncoated ones. The AE 435 superalloy performed better than Superni 718 for hot corrosion in a given environment.

Tool Wear Mechanisms during Machining of Alloy 625

2011 ◽  
Vol 275 ◽  
pp. 204-207 ◽  
Author(s):  
Lenka Fusova ◽  
Pawel Rokicki ◽  
Zdeněk Spotz ◽  
Karel Saksl ◽  
Carsten Siemers
Keyword(s):  
Wear Mechanisms ◽  
Gas Turbines ◽  
Metal Cutting ◽  
Elevated Temperatures ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
Production Costs ◽  
Chemical Compositions ◽  
Alloy 625 ◽  
Wide Range

Nickel-base superalloys like Alloy 625 are widely used in power generation applications due to their unique properties especially at elevated temperatures. During the related component manufacturing for gas turbines up to 50% of the material has to be removed by metal cutting operations like milling, turning or drilling. As a result of high strength and toughness the machinability of Alloy 625 is generally poor and only low cutting speeds can be used. High-speed cutting of Alloy 625 on the other hand gets more important in industry to reduce manufacturing times and thus production costs. The cutting speed represents one of the most important factors that have influences on the tool life. The aim of this study is the analyses of wear mechanisms occurring during machining of Alloy 625. Orthogonal cutting experiments have been performed and different process parameters have been varied in a wide range. New and worn tools have been investigated by stereo microscopy, optical microscopy and scanning electron microscopy. Energy-dispersive X-ray analyses were used for the investigation of chemical compositions of the tool's surface as well as the nature of reaction products formed during the cutting process. Wear mechanisms observed in the machining experiments included abrasion, fracture and tribochemical effects. Specific wear features appeared depending on the mechanical and thermal conditions generated in the wear zones.

Model Combustor to Assess the Oxidation Behavior of Ceramic Materials Under Real Engine Conditions

1999 ◽  
Author(s):  
D. Filsinger ◽  
A. Schulz ◽  
S. Wittig ◽  
C. Taut ◽  
H. Klemm ◽  
...  
Keyword(s):  
High Temperature ◽  
International Development ◽  
Gas Turbines ◽  
Gas Flow ◽  
Oxidation Behavior ◽  
Elevated Temperatures ◽  
Ceramic Materials ◽  
Test Rig ◽  
Combustion Gas ◽  
Wide Range

A further increase of thermal efficiency and a reduction of the exhaust emissions of ground based gas turbines can be achieved by introducing new high temperature resistant materials. Therfore, ceramics are under international development. They offer excellent strengths at room and elevated temperatures. For gas turbine combustor applications, however, these materials have to maintain their advantageous properties under hostile environment. For the assessment and comparison of the oxidation behavior of different nonoxide ceramic materials a test rig was developed at the Institute for Thermal Turbomachinery (ITS), University of Karlsruhe, Germany. The test rig was integrated into the high temperature/ high pressure laboratory. A ceramic model combustion chamber was designed which allowed the exposure of standard four-point flexure specimens to the hot combustion gas flow. Gas temperatures and pressures could be varied in a wide range. Additionally, the partial steam pressure could be adjusted to real combustor conditions. The present paper gives a detailed description of the test rig and presents results of 100 hours endurance tests of ceramic materials at 1400°C. The initial strengths and the strengths after oxidation tests are compared. In addition to this, photographs illustrating the changes of the material’s microstructure are presented.

scholarly journals Characterization of Cobalt-Based Stellite 6 Alloy Coating Fabricated by Laser-Engineered Net Shaping (LENS)

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7442
Author(s):  
Tomasz Durejko ◽  
Magdalena Łazińska
Keyword(s):  
Elevated Temperatures ◽  
Protective Coatings ◽  
Alloy Coating ◽  
Chemical Homogeneity ◽  
X Ray ◽  
Laser Engineered Net Shaping ◽  
Stellite 6 ◽  
Manufacturing Techniques ◽  
Net Shaping ◽  
Corrosive Environments

The results of microstructure and mechanical properties evaluation of a Stellite 6 (Co-6) alloy deposited on X22CrMoV12-1 substrate by the laser-engineered net shaping (LENSTM) technology are presented in this paper. The Stellite 6 alloy is widely used in industry due to its excellent wear resistance at elevated temperatures and corrosive environments. Specific properties of this alloy are useful in many applications, e.g., as protective coatings in steam turbine components. In this area, the main problems are related to the fabrication of coatings on complex-shaped parts, the low metallurgical quality of obtained coatings, and its insufficient adhesion to a substrate. The results of recently performed investigations proved that the LENS technology is one of the most effective manufacturing techniques of the Co-6 alloy coatings (especially deposited on complex-shaped turbine parts). The microstructural and phase analyses of obtained Stellite 6 coatings were carried out by light microscopy techniques and X-ray diffraction analysis. A chemical homogeneity of Co-6 based layers and a fluctuation of chemical composition in coating–substrate zone after the laser deposition were analyzed using an energy dispersive X-ray spectrometer coupled with scanning electron microscopy. The room temperature strength and ductility of the LENS processed layers were determined in static bending tests.

Experience With in 939 as a Hot Corrosion Resistant Turbine Vane Material

1984 ◽  
Author(s):  
Klaus Schneider ◽  
Roland Bauer ◽  
Marc Staubli ◽  
Hermann W. Grünling
Keyword(s):  
Hot Corrosion ◽  
Gas Turbines ◽  
Protective Coatings ◽  
Base Alloy ◽  
Corrosion Resistant ◽  
Term Operation ◽  
Actual Application ◽  
M Phase ◽  
Nickel Base ◽  
And Behavior

For stationary gas turbine vanes IN 939 was evaluated very thoroughly in Europe as a promising hot corrosion resistant nickel base alloy. This paper shows examples of properties and behavior of IN 939 from literature and from actual application in stationary gas turbines. After long-term operation in stationary gas turbines vanes are analysed to show the type of oxide scale formation, the hot corrosion attack and phase stability. The alloy IN 939 exhibited excellent hot corrosion resistance under severe environmental conditions comparable to that of commercial hot corrosion protective coatings. Phases are described developed after casting and during heat treatment and sensitivity towards M-phase formation is briefly discussed. Creep and fatique data of IN 939 are compared with IN 738 LC as well as the hot corrosion behavior.

Improving the hot corrosion resistance of boiler tube steels by detonation gun sprayed coatings in actual boiler of thermal power plant

2019 ◽  
Vol 66 (4) ◽  
pp. 394-402
Author(s):  
Vikramjit Singh ◽  
Khushdeep Goyal ◽  
Rakesh Goyal
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Hot Corrosion ◽  
Power Plants ◽  
Thermal Power ◽  
Boiler Steel ◽  
Content Type ◽  
Boiler Environment ◽  
Detonation Gun ◽  
Sprayed Coatings

Purpose This paper aims to investigate the hot corrosion behavior of Ni-Cr and Cr3C2-NiCr coatings, deposited on T11, P91 boiler steels by detonation gun spray coating (D-Gun) process to enhance high temperature corrosion resistance. Design/methodology/approach Hot corrosion studies were conducted in secondary super heater zone of boiler at 900 °C for 10 cycles on bare and D-Gun coated steel specimens. The microhardness and porosity values of as-sprayed coatings were measured before exposing the specimens in the boiler environment. Each cycle consisted 100 h of heating in the boiler environment followed by 20 min of cooling in air. The weight change measurements were performed after each cycle to establish the kinetics of corrosion using thermogravimetric technique. X-ray diffraction, SEM techniques were used to analyze the corroded specimens. Findings Uncoated boiler steel experienced higher weight loss. The Cr3C2-NiCr coating was found to be more protective than Ni-Cr coating. The phases revealed the formation of oxide scale on coated specimens, mainly consist of nickel and chromium, which are reported to be protective against the hot corrosion. Originality/value There is very limited reported literature on hot corrosion behavior of Ni-Cr and Cr3C2-NiCr coatings deposited on the T11 and P91 substrates by detonation gun (D-gun) spray technique. T11 and P91 alloy steels have been chosen for this study because these two alloys are used to manufacture boiler tubes used in Indian thermal power plants.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Sign in / Sign up

Export Citation Format

Share Document