The Behavior of Valve Materials Utilized in Diesel Engines Under Thermal Shock Conditions (original) (raw)
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Thermal Shock Corrosion of Valve Steels Utilized in Automobile Industry
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The high-temperature corrosion behavior of four valve steels (X33CrNiMn23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8) in combustion gases of fuel oil, containing different concentrations of bio-components (5 and 10 wt%) has been studied under thermal shock conditions. It was found that the addition of bio-components decreased the corrosion resistance of steels investigated. It was also found that the X33CrNiMn23-8 steel containing the highest chromium concentration, behaved in the investigated atmospheres much better than three remaining steels due to the formation of highly protective chromia scale.
Oxidation Kinetics of Steels Utilized in the Production of Valves in Automobile Industry
High Temperature Materials and Processes, 2012
The oxidation kinetics of four Fe-Cr-Mn-Ni based steels, utilized in automobile industry, have been studied as a function of temperature (973-1273 K) and oxygen partial pressure (5-10 5 Pa). It has been shown that the rate of corrosion of these steels under isothermal conditions is determined by diffusion of reagents through the scale, which phase composition and morphology depend first of all on chromium and to some extend also on nickel and manganese contents. The highest oxidation resistance at high temperatures is observed in the case of the X33CrNiMn23-8 steel, containing highest chromium concentration, equal 23.4 wt.% and nickel equal 7.8 wt.%. The remaining three steels with virtually the same chromium content (20 wt.%), but lower than that in the first one, show comparable oxidation resistance. Small differences in the oxidation rates of these three steels may be related to different nickel and manganese contents. It has been found also that the rate of corrosion of all steels under investigation does not depend under steady state conditions on oxygen partial pressure.
2014
The corrosion resistance of widely used X50CrMnNiNbN21-9 high-alloyed austenite valve steel in three different combustion gases have been compared.The comparison was performed on the basis of results of kinetic corrosion of the tested steel in combustion gases from propane-butane, gasoline with 5 and 10% of ethanol additives (v/v) and fuel oil with 5 and 10% of FAME additives (v/v). The corrosion test was performed gravimetrically under thermal shock conditions by heating samples of the test steels from room temperature up to 1173 K in exhaust gases from a combustion engine, and holding them at this temperature for 2 hrs. and then cooling at room temperature for about 25 min. Then the same thermal shock was repeated and after every 10 to 20 such cycles the mass of the samples were measured. This experiment simulated the working conditions of a highly thermal loaded exhaust valves in spark or self-ignited combustion engines. The analysis performed shows that the corrosion resistance ...
2014
The corrosion resistance of three grades of valve steels (X33CrNiMn23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8) in combustion gases of propane-butane (LPG) under thermal shock conditions has been studied. It was stated that X33CrNiMn23-8 steel, containing highest concentration of chromium and nickel and also the lowest of manganese concentration, showed the best corrosion resistance in comparison to another tested steels. The worse corrosion resistance in combustion gases of propane-butane (LPG) was stated in reference to X50CrMnNiNbN21-9 and X53CrMnNiN20-8 valve steels containing lower chromium and nickel concentrations.
Materiali in tehnologije
The influence of a thin chromium layer (1 μm) sputter-deposited on the surfaces of four valve steels (X33CrNiMn23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8) was studied at 900°C under isothermal and thermal-shock conditions. It was determined that the oxidation resistance of coated steels is much better than that of uncoated ones. This situation is a result of the formation of highly protective Cr2O3 scales on the surfaces of coated materials. It was also demonstrated that a positive effect of a chromium addition on the oxidation resistance of the investigated steels is observed during a much longer period than the lifetime of a chromium coating.
Martensitic steel X20CrMo12.1 has been extensively used within the last few decades as a material for tubing systems and pipelines in thermal power plants (TPP). Long term behavior of this steel is very well known and understood and because of that was found to be reliable material for prolonged service at elevated temperatures. It is well known that during operation TPP components are subject to microstructural changes that inevitably reflect decrease in their mechanical properties that lead to the loss of structural integrity and serviceability of component. This paper deals with the comprehensive investigation carried out on the main steam gate valve parent material of welded joint, as a part of main steam pipeline, after 170.000 h of service (545°C and 19MPa). The obtained results showed that the microstructural degradation caused by long term operation had little effects on the hardness and strength of material, while the changes in impact toughness were observed. Comprehensive...
International Journal of Mechanical Engineering and Robotics Research
The paper aims to study the thermal stresses on an exhaust valve body with and without using the Thermal Barrier Coating technique (TBC) in the valve face region. A 2-dimensional model is created for the numerical analysis. The work is carried out with the aid of the ANSYS-APDL package. The procedure of the numerical analysis is divided into two processes. The first process is the thermal analysis to obtain the temperature values, which are set up as thermal loads for the structural analysis in the second process. The coating of the valve is carried out through three steps of analysis by selecting a single layer of TBC, a double layer of TBC, and a triple layer of TBC. Three types of TBC materials are taken in this work, which are SiO2, Al2O3, and ZrO2. The location of TBC type for the double and triple cases is taken into consideration, in the steps of analysis of double and triple design of exhaust vale coating is done by changing of the material type of TBC which it is on the upper or lower concerning the valve face. The results showed that using the SiO2 material as a TBC in the case of single, double, and triple coating of the exhaust valve face gives a low value of thermal deformations and thermal stresses. The stresses in steel alloy in cases without and with TBCs as compared to titanium valve showed a good reduction in thermal stresses for the titanium aluminide exhaust valve.
Oxidation resistance of valve steels covered with thin SiC coatings, obtained by RF CVD
Corrosion Science, 2018
Oxidation studies at 1173 K under isothermal and thermal shock conditions performed on four different valve steels (X33CrNiMn23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8) covered with a 2 μm thick SiC coating revealed that they exhibit greater corrosion resistance compared to the uncoated steels. This is due to the formation of highly protective MnCr 2 O 4 on coated samples in contrast to uncoated materials, on which Fe 3 O 4 and Fe 2 O 3 oxides with poor protective properties are detected. Studies performed in compressed natural gas also demonstrate the positive effect of SiC application. Obtained results enable tailoring a new generation of inexpensive coating for engine valve protection.
The Influence of Hybrid Coatings on Scaling-Resistant Properties of X33CrNiMn23-8 Steel
High Temperature Materials and Processes, 2007
The influence of two-layer hybrid coatings on the oxidation behavior of X33CrNiMn23-8 steel, utilized in valves of Diesel engines, have been studied as a function of temperature (873-1273 K) and oxygen pressure (1-10 5 Pa), using modern microthermogravimetric techniques. Phase composition of the oxidation products (scale) was investigated by X-ray diffraction (XRD), and the morphology and chemical composition of reaction products by electron probe micro analysis (ΕΡΜΑ) and scanning electron microscopy (SEM) with energy disperse X-ray analyzer (EDX). It has been found that uncoated material shows very good oxidation resistance under isothermal conditions, comparable with that of chromia formers, due to the formation on its surface of Cr 2 0 3 scale. However, beneath the scale, steel undergoes rapid degradation, as a result of crack formation; the deeper the penetration, the longer is the oxidation time. On the other hand, no cracks were observed in the coated steel and the oxidation rate was even slightly lower than that of uncoated material.
Fatigue Strength of X45CrSi93 stainless steel applied as internal combustion engine valves
Procedia Engineering, 2011
Stainless steels are used to intake and exhaust valves production applied as internal combustion engines. In general valves are requested to support cyclic stresses applied due to opening and closing processes during the operation. The objective of this research is to study the influence on the axial fatigue strength of the resulting microstructure after heat treatment at the martensitic X45CrSi93 steel, combined with different surface treatments as hard chrome-plating, nitride and grinding. It was verified a significant increase on the fatigue strength of the martensitic steel after nitriding, compared with results from the chrome-plating specimens. A slight increase in the tensile strength was also noticed on nitrided parts as a consequence of a resistance increase due to nitrogen and carbon solid solution.