The modeling of thermal residual stresses generated in TaC/stellite and TiC/stellite composite surface layers produced by the oscillating electron beam remelting on low alloys steel is presented. The homogenization method is applied to analyze the real composite microstructures by utilizing the digital image-based (DIB) geometric modeling technique. Two scales of elastic stress analysis are studied: macroscopic one referring to the global structure of composite layer produced over the substrate of low alloy steel and microscopic, comprising the selected unit cell of composite microstructure.The results of the analysis show the microscopic stress to be few times higher than the macroscopic one with stress level much above the elastic limit of matrix material, which implies the development of plastic field around the inclusions. The ceramic inclusions within the unit cell are found to be under high compressive stresses. Also, the composite surface layer stays in compression, mainly by the influence of the stress component parallel to the layer/ substrate interface. The effect of hardphase volume fraction is examined and it is found that for a small volume fractions the macro and micro stress does not differ substantially between composites with TaC and TiC hardphases despite their mismatch in thermophysical properties. Also, the stress modeling is presented for the composite containing other inclusions and the problem of the selection between 2D and 3D model for the stress analysis is discussed. IntroductionThere are several industry fields like aircraft, electrical, nuclear or building where metal matrix composites (MMC) are preferably used for engineering applications reducing the use of traditional materials. High strength of MMC together with high stiffness and high thermal stability at elevated temperatures makes them very attractive for engineering structures.One of the fields where application of MMC can be beneficial are composite surface layers produced over a substrate of conventional material. The role of a surface layer is to secure the surface of material against the action of external factors like corrosion as well as mechanical factors (intensive wear, cycling loading) resulting in the excessive wear of material during service life (Rohatgi et al. (1994)). An example of application of composite surface layers is for many machine parts and tools (e.g. drilling and boring tools) which are often subject to extreme working conditions. Although the commonly used materials for such applications are characterized by high strength, wear and corrosion resistance, yet there is still need to improve the service condition for this kind of layers because of the increase of working temperatures and loads. The metal matrix composite may be suitable for this purpose as their unique properties can sustain these demanding service conditions. By embedding hard ceramics in the form of fibers, whiskers or particulates into the metal matrix, we can expect the hard inclusions to carry on the main load resulting from the in...
The paper describes the microstructure of welded joints produced by the plasma+MAG (Metal Active Gas) method of S700MC high yield strength steel (700 MPa). Welded joints of thermomechanical steel have been made with different values of heat input. The results of metallographic research of welded joints, microstructure of the weld and heat affected zone, hardness distribution and impact toughness are presented. The heat affected zone consists of two sub-zones with different grain size and lowered hardness. The tensile test show that strength of welded joints was slightly reduced and the bending test revealed no crack formation in the weld. The impact toughness of measured welded samples with V-notch in HAZ (heat affected zone) reached high values that are higher comparing to samples with notch placed in the weld area. The investigation results show that the use of plasma concentrated heat source together with MAG welding arc does not significantly change the structure and deteriorate properties of welded S700MC thermomechanically treated high strength steel. The hybrid plasma+MAG welding method has a potential to become a beneficial alternative to other welding processes due to its high efficiency, reduced amount of weld metal content or limited requirements for a preparation of edges of welded joints.
The paper presents the results of research on the production by means of arc spraying of composite coatings from the Fe-Al system with participation of in-situ intermetallic phases. The arc spraying process was carried out by simultaneously melting two different electrode wires, aluminum and steel. The aim of the research is to create protective coatings with a composite structure with a significant participation of FexAly as an intermetallic phases reinforcement. The synthesis of intermetallic phases takes place during the (in-situ) spraying process. Currently most coatings involving intermetallic phases are manufactured by different thermal spraying methods using coating materials in the form of prefabricated powders containing intermetallic phases. The obtained results showed the local occurrence of intermetallic phases from the Fe-Al system, and the dominant components of the structure have two phases, aluminum solid solutions in iron and iron in aluminum. The participation of intermetallic phases in the coating is relatively low, but its effect on the properties of the coating material is significant.
The paper presents the initial investigation results on producing surface protective coatings made of Fe–Al intermetallic compounds on steel substrates. The Fe–Al coating is obtained in a two-step process. First, the steel substrate is thermally sprayed with pure aluminium having a thickness of about 0.3° mm. In this way both components (Fe, Al) are prepared for subsequent melting and synthesis. In the final step, the aluminium coating is remelted together with the surface of the steel substrate by the CO2 laser beam. The resulting molten pool consists of aluminium and iron in equal parts, allowing it to form a Fe–Al intermetallic compound during the in-situ process of remelting. The formation of Fe–Al intermetallic compound has been verified by the microhardness and X-ray diffraction measurements of the analysed coatings. The developed method is a cheap alternative compared with other surface modification processes utilizing commercially prepared intermetallic coating materials. In addition, the remelting process substantially increases the strength of the coating bond, which has a magnitude close to that observed for hard-facing processes.
There is described a method of modeling by the finite element method the residual stresses induced during thermal deposition of coatings. The simulation was performed in two stages. The first dynamic stage simulated the impacts of the individual particles of the coating material onto the substrate, and the next static stage included a non-linear thermo-mechanical analysis intended for simulating the process of layer-by-layer deposition of the coating, with a specified thickness, and then cooling the entire system to the ambient temperature. In the computations, the samples were assumed to be cylindrical in shape and composed of an Al2O3 substrate and a titanium coating (with three different thicknesses) deposited using the detonation method. The correctness of the numerical model was verified experimentally by measuring the deflections of a real Ti coating/Al2O3 substrate sample with the Ti coating detonation-sprayed on the ceramic substrate, after cooling it to the ambient temperature. The experimental results appeared to be in good agreement with those obtained by the numerical computations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.