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Book ChapterDOI

Laser surface modification of steel for slurry erosion resistance in power plants

TL;DR: In this article, the microstructure and slurry erosion characteristics of laser surface alloyed coatings that are used to mitigate the erosion issues of 13Cr-4Ni martensitic stainless steel are discussed.
Abstract: This chapter discusses the microstructure and slurry erosion characteristics of laser surface alloyed coatings that are used to mitigate the erosion issues of 13Cr–4Ni martensitic stainless steel. The chapter first describes the present scenario of surface modification methods, such as conventional welding, surface hardening/nitriding, external coatings, etc., which are being utilized to minimize the silt erosion problems of components in hydropower plants. The chapter also explains newer coating methods, such as laser surface alloying. It then describes the usefulness towards erosion mitigation in hydropower plant applications of laser surface alloying of 13Cr–4Ni steels with commercial coating powders such as Colmonoy 88 and Stellite 6. Erosion performances of coatings and substrates are evaluated using a slurry jet erosion test-rig with various parameters, using commercial silica sand and river sand. An evaluation of the effect of boron carbide addition on the erosion performances of laser surface alloyed coatings is given. An attempt has also been made to correlate the quantitative results (erosion performances) with qualitative results (erosion mechanisms) by extensive studies of eroded samples using scanning electron microscopy. By the end of the chapter, a correlation between measured and predicted erosion rates has been established in power-law formulation.
Citations
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Journal ArticleDOI
TL;DR: In this article, the performance of modified surfaces, which have been developed by using various surface engineering techniques to combat the slurry erosion failure in hydrodynamic turbines, is reviewed and the evaluation of enhancement in the coating characteristics (mechanical and micro-structural) as well as coating efficiency under different slurry degradation conditions are reported.

46 citations

Journal ArticleDOI
09 Sep 2022-Coatings
TL;DR: In this paper , the authors present a high-level overview of the many coating processes and design procedures employed for thermal barrier coatings to enhance the coating's surface quality, focusing on the cultivation, processing and characteristics of engineered TBCs.
Abstract: Thermal barrier coating is critical for thermal insulation technology, making the underlying base metal capable of operating at a melting temperature of 1150 °C. By increasing the temperature of incoming gases, engineers can improve the thermal and mechanical performance of gas turbine blades and the piston cylinder arrangement. Recent developments in the field of thermal barrier coatings (TBCs) have made this material suitable for use in a variety of fields, including the aerospace and diesel engine industries. Changes in the turbine blade microstructure brought on by its operating environment determine how long and reliable it will be. In addition, the effectiveness of multi-layer, composite and functionally graded coatings depends heavily on the deposition procedures used to create them. This research aims to clarify the connection between workplace conditions, coating morphology and application methods. This article presents a high-level overview of the many coating processes and design procedures employed for TBCs to enhance the coating’s surface quality. To that end, this review is primarily concerned with the cultivation, processing and characteristics of engineered TBCs that have aided in the creation of specialized coatings for use in industrial settings.

20 citations

Journal ArticleDOI
TL;DR: In this article, the nanohardness and elastic modulus of the cross section of a nitrided 13/4 Martensitic stainless steel (13/4HTT) were measured by nanoindentation test using Hysitron TI950 triboindenter.
Abstract: Low-temperature salt bath nitriding of heat treated and tempered 13/4 Martensitic stainless steel (13/4HTT) was carried at 450 °C (N450) and 500 °C (N500) for 10 h each. The nitrided samples were characterized by using x-ray diffractometer, field emission scanning electron microscope and optical microscope. The nanohardness and elastic modulus of the cross section of nitrided specimen were measured by nanoindentation test using Hysitron TI950 triboindenter. The nitrided 13/4HTT (N450 and N500) and 13/4HTT specimens were subjected to slurry erosion test in a slurry pot tester. The test was conducted for 48 h, and weight loss was measured after every 6 h. The relative speed of slurry with respect to specimen was 4.55 m/s. It was found that the weight loss due to erosion of the N450 is 83% less than that of 13/4HTT and that of N500 was 92% more than that of 13/4HTT. The erosion mechanism is correlated to the phases present in the specimens. The improvement in the slurry erosion resistance of N450 is due to presence of expanded martensite ( $$\alpha_{N}$$ -Fe). Increasing the temperature of nitriding to 500 °C led to the decrease in the slurry erosion resistance of N500 due to the formation of brittle CrN phase.

16 citations

Journal ArticleDOI
TL;DR: In this article, the evolution of the multi-scale microstructure of a (Zr,Ta)B2 solid solution was studied as a function of time and temperature, and phase stability diagrams were used to define the conditions of partial pressure within the sintering chamber that drove precipitation of nanoinclusions in the form of either metal or carbide.
Abstract: The evolution of the multi-scale microstructure of a (Zr,Ta)B2 solid solution was studied as a function of time and temperature. The ceramics were produced by hot pressing a mixture of ZrB2 with 15 vol% TaSi2 followed by annealing at 2100 °C. Formation of a super-saturated solid solution led to the precipitation of TaC nano-needles within the micron-sized boride grain matrix. Phase stability diagrams were used to define the conditions of partial pressure within the sintering chamber that drove precipitation of nano-inclusions in the form of either metal or carbide. Through this approach, other systems containing various transition metals were explored to design other formulations for in-situ nano-composites with unprecedented strength at ultra-elevated temperatures.

8 citations

Journal ArticleDOI
TL;DR: In this paper , a comparison of microhardness, fatigue and high temperature corrosion of Inconel 740H nickel alloy in its as-received state and the same material with nitrided surface layers was presented.

1 citations

References
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Book
12 Mar 2014
TL;DR: In this paper, the effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1).
Abstract: In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

1,539 citations

Book
01 Jan 2002
TL;DR: In this article, the authors present a theory of the real area of contact (ROC) between two surfaces and show that the ROC can be represented as a triangle of a triangle.
Abstract: Foreword. Preface. 1 Introduction. 1.1 De.nition and History of Tribology. 1.2 Industrial Signi.cance of Tribology. 1.3 Origins and Signi.cance of Micro/Nanotribology. 1.4 Organization of the Book. References. 2 Solid Surface Characterization. 2.1 The Nature of Surfaces. 2.2 Physico-Chemical Characteristics of Surface Layers. 2.3 Analysis of Surface Roughness. 2.4 Measurement of Surface Roughness. 2.5 Closure. References. Suggested Reading. 3 Contact between Solid Surfaces. 3.1 Introduction. 3.2 Analysis of the Contacts. 3.3 Measurement of the Real Area of Contact. 3.4 Closure. References. Suggested Reading. 4 Adhesion. 4.1 Introduction. 4.2 Solid-Solid Contact. 4.3 Liquid-Mediated Contact. 4.4 Closure. References. Suggested Reading. 5 Friction. 5.1 Introduction. 5.2 Solid-Solid Contact. 5.3 Liquid-Mediated Contact. 5.4 Friction of Materials. 5.5 Closure. References. Suggested Reading. 6 Interface Temperature of Sliding Surfaces. 6.1 Introduction. 6.2 Thermal Analysis. 6.3 Interface Temperature Measurements. 6.4 Closure. References. 7 Wear. 7.1 Introduction. 7.2 Types of Wear Mechanisms. 7.3 Types of Particles Present in Wear Debris. 7.4 Wear of Materials. 7.5 Closure. References. Suggested Reading. 8 Fluid Film Lubrication. 8.1 Introduction. 8.2 Regimes of Fluid Film Lubrication. 8.3 Viscous Flow and Reynolds Equation. 8.4 Hydrostatic Lubrication. 8.5 Hydrodynamic Lubrication. 8.6 Elastohydrodynamic Lubrication. 8.7 Closure. References. Suggested Reading. 9 Boundary Lubrication and Lubricants. 9.1 Introduction. 9.2 Boundary Lubrication. 9.3 Liquid Lubricants. 9.4 Greases. 9.5 Closure. References. Suggested Reading. 10 Micro/Nanotribology. 10.1 Introduction. 10.2 SFA Studies. 10.3 AFM/FFM. 10.4 Atomic-Scale Simulations. 10.5 Closure. References. Suggested Reading. 11 Friction and Wear Screening Test Methods. 11.1 Introduction. 11.2 Design Methodology. 11.3 Typical Test Geometries. 11.4 Closure. References. Suggested Reading. 12Tribological Components and Applications. 12.1 Introduction. 12.2 Common Tribological Components. 12.3 Microcomponents. 12.4 Material Processing. 12.5 Industrial Applications. 12.6 Closure. References. Suggested Reading. Problems. Appendix Units, Conversions, and Useful Relations. A.1 Fundamental Constants. A.2 Conversion of Units. A.3 Useful Relations. Index.

1,375 citations

Journal ArticleDOI
J.G.A. Bitter1
01 Jan 1963-Wear
TL;DR: In this article, the authors derived an expression for the energy needed to remove a unit volume of material from the body surface and described the plastic-elastic behaviour of the substance.

1,075 citations

Journal ArticleDOI
01 Jan 1972-Wear
TL;DR: In this paper, the effect of some of these variables may be predicted on simple fundamental grounds, and quantitative predictions may be made for the erosion of ductile metals by hard abrasive grains which strike at grazing angles.

430 citations

Journal ArticleDOI
TL;DR: An overview of laser-assisted forming, joining, machining and surface engineering can be found in this paper, where a review of the relevant literature is presented to highlight the recent advances and open questions.
Abstract: Light amplification by stimulated emission of radiation (laser) is a coherent and monochromatic beam of electromagnetic radiation that can propagate in a straight line with negligible divergence and occur in a wide range of wave-length, energy/power and beam-modes/configurations. As a result, lasers find wide applications in the mundane to the most sophisticated devices, in commercial to purely scientific purposes, and in life-saving as well as life-threatening causes. In the present contribution, we provide an overview of the application of lasers for material processing. The processes covered are broadly divided into four major categories; namely, laser-assisted forming, joining, machining and surface engineering. Apart from briefly introducing the fundamentals of these operations, we present an updated review of the relevant literature to highlight the recent advances and open questions. We begin our discussion with the general applications of lasers, fundamentals of laser-matter interaction and classification of laser material processing. A major part of the discussion focuses on laser surface engineering that has attracted a good deal of attention from the scientific community for its technological significance and scientific challenges. In this regard, a special mention is made about laser surface vitrification or amorphization that remains a very attractive but unaccomplished proposition.

420 citations