Ni20Cr coating on T24 steel pipes by HVOF thermal spray for high temperature protection

C. C. Berndt advanced investigations of mechanical properties of thermal spray coatings under 4-point bending. He found that this investigation method is sensitive to the mechanical properties of thermal spray coatings.This paper contains the detailed investigation results for thermal spray coatings of zirconium dioxide under 4-point bending, i.e. tests of the specimens subjected to spraying at varying conditions and pre-test soaking with the various duration at 1100 °С.It was established how the mechanical properties of thermal spray coatings changed depending on the spraying mode and high temperature soaking. The test results show that the double heat treatment of coatings is more preferable than one-time heat treatment as it make the properties change linearly. It is more easily controllable during operation of the components with thermal spray coating.

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Advances in Corrosion-Resistant Thermal Spray Coatings for Renewable Energy Power Plants: Part II—Effect of Environment and Outlook

Journal of Thermal Spray Technology ◽

10.1007/s11666-019-00939-0 ◽

2019 ◽

Vol 28 (8) ◽

pp. 1789-1850 ◽

Cited By ~ 4

Author(s):

Esmaeil Sadeghi ◽

Nicolaie Markocsan ◽

Shrikant Joshi

Keyword(s):

High Temperature ◽

Thermal Spray ◽

Power Plants ◽

High Temperature Corrosion ◽

Thermal Spray Coatings ◽

Current Status ◽

Comprehensive Overview ◽

Biomass Waste ◽

Corrosion Resistant ◽

Spray Coatings

Abstract High-temperature corrosion of critical components such as water walls and superheater tubes in biomass/waste-fired boilers is a major challenge. A dense and defect-free thermal spray coating has been shown to be promising to achieve a high electrical/thermal efficiency in power plants. The field of thermal spraying and quality of coatings have been progressively evolving; therefore, a critical assessment of our understanding of the efficacy of coatings in increasingly aggressive operating environments of the power plants can be highly educative. The effects of composition and microstructure on high-temperature corrosion behavior of the coatings were discussed in the first part of the review. The present paper that is the second part of the review covers the emerging research field of performance assessment of thermal spray coatings in harsh corrosion-prone environments and provides a comprehensive overview of the underlying high-temperature corrosion mechanisms that lead to the damage of exposed coatings. The application of contemporary analytical methods for better understanding of the behavior of corrosion-resistant coatings is also discussed. A discussion based on an exhaustive review of the literature provides an unbiased commentary on the advanced accomplishments and some outstanding issues in the field that warrant further research. An assessment of the current status of the field, the gaps in the scientific understanding, and the research needs for the expansion of thermal spray coatings for high-temperature corrosion applications is also provided.

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Cyclone Maintenance Improvement via Special Refractory Anchor Pin Studs

ASME 2004 Power Conference ◽

10.1115/power2004-52183 ◽

2004 ◽

Author(s):

Stephen R. Swartz

Keyword(s):

Stainless Steel ◽

High Temperature ◽

Thermal Cycling ◽

Thermal Spray ◽

Effective Means ◽

Protective Layer ◽

Spray Coating ◽

Cycle Performance ◽

Alloy 625 ◽

430 Stainless Steel

Since the inception of the cyclone style boiler, industry has become accustomed to performing routine maintenance during every scheduled shutdown occurring 12 months to 18 months between cycles. These maintenance cycles are influenced by service factor, loading and the type design. The same problems exist in both the standard and super critical cyclones; severe deterioration of refractory and the anchoring pin studs. This paper focuses on one type of refractory failure mechanism caused by the anchoring pin studs. Most operators have found that the most effective means of applying refractory in this type situation is to “ram” the refractory in and around the anchoring pin studs thus creating a dense lining with maximum integrity. Coupled with proper application of anchoring pin studs and a special designed coating, typical volumetric expansion of the pin studs from corrosion attack and oxidation is eliminated thus extending the life of the refractory. This mechanism is discussed along with the results of the coating performance as it relates to extreme heat oxidation and thermal cycling in laboratory tests. A protective coating was developed using a nano-cored thermal spray wire technology that produces a uniform, adherent protective layer against high temperature corrosion and oxidation. The coating yields similar thermal conductivity as a bare stud thus experiencing excellent thermal cycle performance. This specially designed thermal spray coating is applied to standard 430 stainless steel pin studs thus providing the necessary barrier against aggressive high temperature environments while maintaining excellent heat conductivity. The coating has a high amount of tungsten (40+%) in a nickel matrix with greatly reduced oxides at the substrate and throughout the coating. With these attributes for the anchoring pin studs in mind, a newly designed stud was evaluated in heat oxidation tests up to 2000°F and thermal cycling test and compared to 430 stainless steel, chromized and Alloy 625. The new stud out-performed all others even in the as-welded condition. Further corrosion testing in ferric chloride (ASTM G48) showed them to be superior to Alloy 72 and Alloy 625 in the thermal spray and welded condition. Proper welding equipment and welding techniques are also discussed since weld continuity impacts overall performance of anchoring pin studs with refractory linings. A major test site will be examined in the spring of 2004 for it’s full effectiveness in service and will be documented in order that all data retrieved would be available to the entire industry.

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Computational Fluid Dynamics Analysis of a Wire-Feed, High-Velocity Oxygen Fuel (HVOF) Thermal Spray Torch

CrossRef Listing of Deleted DOIs ◽

10.1361/105996398770350855 ◽

1998 ◽

Vol 7 (3) ◽

pp. 374-382 ◽

Cited By ~ 19

Author(s):

A.R. Lopez ◽

B. Hassan ◽

W.L. Oberkampf ◽

R.A. Neiser ◽

T.J. Roemer

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Thermal Spray ◽

High Velocity ◽

Dynamics Analysis ◽

High Velocity Oxygen Fuel ◽

Hvof Thermal Spray ◽

Computational Fluid Dynamics Analysis ◽

Oxygen Fuel ◽

Wire Feed

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Image-Based Modeling for Assessing Thermal Conductivity of Thermal Spray Coatings at Ambient and High Temperature

Heat Transfer, Volume 2 ◽

10.1115/imece2006-15972 ◽

2006 ◽

Cited By ~ 1

Author(s):

Y. Tan ◽

A. Sharma ◽

J. P. Longtin ◽

S. Sampath ◽

H. Wang

Keyword(s):

Thermal Conductivity ◽

High Temperature ◽

Thermal Spray ◽

Process Parameters ◽

Thermal Spraying ◽

Thermal Spray Coatings ◽

Analysis Model ◽

Element Analysis ◽

Spray Coatings ◽

Coating Microstructure

Thermal spray coatings are used extensively for protection of engineering components and structures in a variety of applications. Due to the nature of thermal spraying process, the coating thermal, mechanical, and electrical properties depend strongly on the coating microstructure, which consists of many individual splats, interfaces between the splats, defects and voids. The coating microstructure, in turn, is determined by the thermal spray process parameters. In order to relate coating process parameters to the final coating performance, then, it is desirable to relate coating microstructure to coating properties. In this work, thermal conductivity is used as the physical parameter of interest. Thermal conductivity of thermal spray coatings is studied by using an image analysis-based approach of typical coating cross sections. Three coating systems, yttria stabilized zirconia (YSZ), molybdenum, and Ni-5wt.%Al are explored in this work. For each material, thermal conductivity is simulated by using a microstructure image-based finite element analysis model. The model is then applied to high temperature conditions (up to 1200 °C) with a hot stage-equipped scanning electron microscope imaging technique to assess thermal conductivity at high temperatures. The coating thermal conductivity of metallic coatings is also experimentally measured by using a high-temperature laser flash technique.

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