scholarly journals STATE IN THE FIELD OF HEAT-RESISTANT COATINGS FOR HEAT-PROOF NICKEL ALLOYS AND STEELS

2019 ◽  
Vol 16 (33) ◽  
pp. 561-572
Author(s):  
V. S. TERENTIEVA ◽  
A. N. ASTAPOV ◽  
L. N. RABINSKIY

Currently, in many industries, special attention is paid to increasing the reliability and economy of the products. Solving problems requires the use of materials that can work in difficult conditions, which determines the relevance of the problem stated in the article. The purpose of the article was to conduct a critical analysis of coatings developed in Russia that are diverse in composition, technological and operational properties, from the standpoint of the possibility of using them to provide a reliable material protection system under conditions that cause high-temperature gas corrosion and surface layer erosion. The main methods of materials protection were considered in the work: thermal spraying, plasma spraying, electron beam, plasma electric arc cathode spraying, vacuum deposition, chemical-thermal treatment, diffusion coating based on aluminum. Among the more effective methods, the method of self-propagating high-temperature synthesis, the method of high-energy plasma chemistry, the methods of physical deposition in vacuum are noted. The types of coatings were also highlighted and their short characteristics were given. Particular attention was paid to heat-resistant coatings based on refractory enamels since their advantages include low cost and the possibility of applying them directly to parts. A number of technical solutions have been identified that protect the alloys from high-temperature gas corrosion and erosion under long-term operation in aircraft products at high temperatures. The results of the article may be useful for further research since individual developments are uninformative from the standpoint of solving specific problems and require expensive bench testing of the claimed technical result.

2018 ◽  
pp. 4-13
Author(s):  
Сергей Игоревич Планковский ◽  
Евгений Сергеевич Палазюк ◽  
Вадим Олегович Гарин ◽  
Юрий Вениаминович Дьяченко

One of the most important parts of gas turbine engines (GTE) are turbine blades, because from their operational characteristics depend the maximum gas temperature in a turbine, its reliability and service life, specific power and economy of an engine. Different mechanical damages, cracks, traces of general corrosion, changing their working section, are unacceptable on blades. Analysis of main causes of the parts destruction in GTE flow section shows that in most cases formation of shearing distortions and cracks occurs on blades edges in the surface layer of material. The main reason for appearance of these defects are sulphide-oxide and high-temperature gas corrosion. The basic development tendencies of blades reliability increasing show, that together with the development of new heat-resistant alloys another possible way to prevent the destruction of blade material is increasing of blade manufacturing quality. The final shape of turbine blades is often achieved by machining, which leads to formation of burrs on the edges. Thermal pulse deburring has a large number of technological advantages and is the most promising method for finishing treatment of the surfaces and edges of GTE blades. However, despite the numerous positive examples of the application of laser treatment of blade surfaces in order to increase the corrosion resistance, the mechanism of phase and structural transformations, occurring in the surface layers of heat-resistant steels and alloys of different compositions, is still not fully understood. To estimate the effect of thermal pulse deburring of gas turbine blades on their operational characteristics, accelerated tests of blade specimens on the tendency to high-temperature gas corrosion have been carried out. The tests consist of sequential chemical etching in electrolyte, electrochemical treatment and high-temperature treatment in aggressive gases. These tests allow to obtain the same corrosion layer on blades surfaces, like after real operation. Also influence of laser deburring on corrosion resistance was estimated in parallel. The experimental study was carried out on the example of treatment of GTE nozzle blades made from a heat-resistant alloy on a nickel basis ZhS26-VI. Specimens were obtained by cutting two new blades into small parts by hydroabrasive cutting method to ensure that there is no thermal impact on the material being processed and no burn-out of the alloying elements. Obtained specimens of GTE blades after the cutting have been undergone by additional machining to obtain burrs at the edges, which were removed by thermal pulse and laser deburring methods. Investigation of the surface layer state of specimens after accelerated tests for high-temperature gas corrosion has been carried out by means of microscopic analysis. For this purpose, microslices of specimens have been prepared. Using a comparative analysis of the corrosion layer thickness after the tests, it was shown that there is no influence of thermal pulse and laser deburring methods on the tendency to high-temperature gas corrosion.


2016 ◽  
Author(s):  
Mitchell Shinn ◽  
Karthik Nithyanandam ◽  
Amey Barde ◽  
Richard Wirz

Currently, concentrated solar power (CSP) plants utilize thermal energy storage (TES) in order to store excess energy so that it can later be dispatched during periods of intermittency or during times of high energy demand. Elemental sulfur is a promising candidate storage fluid for high temperature TES systems due to its high thermal mass, moderate vapor pressure, high thermal stability, and low cost. The objective of this paper is to investigate the behavior of encapsulated sulfur in a shell and tube configuration. An experimentally validated, transient, two-dimensional numerical model of the shell and tube TES system is presented. Initial results from both experimental and numerical analysis show high heat transfer performance of sulfur. The numerical model is then used to analyze the dynamic response of the elemental sulfur based TES system for multiple charging and discharging cycles. A sensitivity analysis is performed to analyze the effect of geometry (system length), cutoff temperature, and heat transfer fluid on the overall utilization of energy stored within this system. Overall, this paper demonstrates a systematic parametric study of a novel low cost, high performance TES system based on elemental sulfur as the storage fluid that can be utilized for different high temperature applications.


2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Michał Dudek ◽  
Zygmunt Kolenda ◽  
Marek Jaszczur ◽  
Wojciech Stanek

Nuclear energy is one of the possibilities ensuring energy security, environmental protection, and high energy efficiency. Among many newest solutions, special attention is paid to the medium size high-temperature gas-cooled reactors (HTGR) with wide possible applications in electric energy production and district heating systems. Actual progress can be observed in the literature and especially in new projects. The maximum outlet temperature of helium as the reactor cooling gas is about 1000 °C which results in the relatively low energy efficiency of the cycle not greater than 40–45% in comparison to 55–60% of modern conventional power plants fueled by natural gas or coal. A significant increase of energy efficiency of HTGR cycles can be achieved with the increase of helium temperature from the nuclear reactor using additional coolant heating even up to 1600 °C in heat exchanger/gas burner located before gas turbine. In this paper, new solution with additional coolant heating is presented. Thermodynamic analysis of the proposed solution with a comparison to the classical HTGR cycle will be presented showing a significant increase of energy efficiency up to about 66%.


2010 ◽  
Vol 638-642 ◽  
pp. 991-996 ◽  
Author(s):  
Claudio Testani ◽  
F. Ferraro

Titanium-alloy matrix composites (TMC) are nowadays one of the material class with the highest specific resistance from room temperature up to 800° C. Centro Sviluppo Materiali SpA (CSM) efforts have been focused on the developing of an innovative solution to reduce the process costs. The new approach consists in an experimental “diffusion bonding” plant for co-rolling at high temperature sheets of titanium alloy and silicon carbide monofilaments fabrics. The result is a process cost reduction of about 40% respect to HIP process. The experimental pilot plant has been proposed for patent with n° 2006A000261 on may 2006. This paper describes the pilot plant and the process results. The metallographic examination on products shows full bonded samples (100 mm wide and 1500 mm long) obtained in a work field that is at least 100 times faster than that of HIP. High temperature tensile tests have been carried on Roll Diffusion Bonded specimens and the results are reported in comparison with those obtained by Isostatic Pressing (HIP) and Thermal- Spraying (TS) processes on the same composite.


2010 ◽  
Author(s):  
Walter Nunez Garcia ◽  
Ricardo Solares ◽  
Jairo Alonso Leal Jauregui ◽  
Jorge E. Duarte ◽  
Alejandro Chacon ◽  
...  

Author(s):  
M V Temlyantsev ◽  
E A Pinaev ◽  
V B Deev ◽  
E N Temlyantseva ◽  
N I Kuvshinnikova

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