Wear surface damage of a Stainless Steel EN 3358 aeronautical component subjected to sliding (original) (raw)
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Wear surface damage of a Stainless Steel EN 3358 aeronautical component subject.PDF
The present paper describes the failure analysis of an aircraft component subjected to several episodes of in service failure, resulted in loss of the aircraft safety. Modern aircrafts are provided with mechanical systems which have the task to open not pressurized hatches during landing. The components of such systems are subject to considerable mechanical stresses in harsh environment (presence of moisture and pollutants, significant and sudden temperature variations). The system is constituted by a sliding piston, a related nipple and by a locking system consisting of 4 steel spheres which are forced into a countersink machined on the piston when the hatches is open. The whole system is activated by a preloaded spring. The machined parts, nipple and piston, are made of EN3358 steel (X3CrNiMo13-8-2), a precipitation hardening stainless steel with very low content of carbon often used in the aerospace. The samples provided by the manufacturer present different types of damage all referable to phenomena relative to the sliding of the piston inside the nipple. The present paper describes the different damage observed and the microstructure of the material, then are reported the results obtained from the characterization of the material of the samples by means of optical and electronic microscopy, carried out to define the mechanisms involved in the system seizure. In order to define the primary cause of failure and to propose solutions to be adopted, also analyzing the criticality of using this PH stainless steel for this application, the results of different tests were compared with system design and working data.
Failure Analysis of Two Stainless Steel Based Components Used in an Oil Refinery
Journal of Failure Analysis and Prevention, 2008
The petroleum industry has changed significantly over the past decades. For example, in Brazil, oil extraction under very deep sea water is growing very quickly. As a consequence, materials and components used for such applications must have properties required to withstand adverse conditions and ensure satisfactory performance and reliability in service. Nonetheless, components that normally fulfill these standard requirements can fail under severe service conditions such as high pressure and temperatures and high concentrations of H2S and CO2, Among the factors that can cause the premature failure in metallic components are the use of inadequate materials, the presence of defects that appeared during the production, and errors of project, assembly, or maintenance. Failure analysis allows the identification of causes and thus contributes to improvements in the operation and performance of similar equipment. In this work, light optical microscopy and scanning electron microscopy (SEM) were used to analyze the microstructure and fracture surface of two centrifugal pump shafts that failed during use in a Brazilian petroleum refinery. The results showed that one shaft, made of duplex stainless steel, failed by fatigue fracture, and the other, made of 316 austenitic stainless steel, experienced a similar fracture, which was promoted by the presence of nonmetallic inclusion particles.
Damage Evolution in Thermomechanical Loading of Stainless Steel
Procedia Structural Integrity, 2016
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Wear, 2015
Fretting is of a serious concern in many industrial components, specifically, in nuclear industry for the safe and reliable operation of various component and/or system. Under fretting condition small amplitude oscillations induce surface degradation in the form of surface cracks and/or surface wear. Comprehensive experimental studies have been carried out simulating different fretting regimes under ambient and vacuum (10 À 9 MPa) conditions and, temperature up to 400 1C. Studies have been carried out with stainless steel spheres on stainless steel flats, and stainless steel spheres against chromium carbide, with 25% nickel chrome binder coatings. Mechanical responses are correlated with the damage observed. It has been observed that adhesion plays a vital role in material degradation process, and its effectiveness depends on mechanical variables such as normal load, interfacial tangential displacement, characteristics of the contacting bodies and most importantly on the environment conditions. Material degradation mechanism for ductile materials involved severe plastic deformation, which results in the initiation or nucleation of cracks. Ratcheting has been observed as the governing damage mode for crack nucleation under cyclic tangential loading condition. Further, propagation of the cracks has been observed under fatigue and their orientation has been observed to be governed by the contact conditions prevailing at the contact interface. Coated surfaces show damage in the form of brittle fracture and spalling of the coatings. Existence of stick slip has been observed under high normal load and low displacement amplitude. It has also been observed that adhesion at the contact interface and instantaneous cohesive strength of the contacting bodies dictates the occurrence of material transfer. The paper discusses the mechanics and mechanisms involved in fretting damage under controlled environment conditions.
Lubricated seizure of stainless steel observed by X-ray imaging
Wear, 2000
Lubricated sliding and seizure of stainless steel is of considerable interest in light of the better properties as it provides improved corrosion resistance, compared to conventional steels. The effect of stainless steel on oil stability during sliding is of importance as it contributes to the wear behaviour of the system. We have used an X-ray microscope for in situ observation of frictional seizure, wear and interfacial features during the testing of stainless steel specimens sliding against Al 6061 disk. This technique enables the observation of interfacial features at the hidden surfaces. Seizure tests were conducted at sliding speeds of 2, 4 and 5 m/s under lubricated conditions with plain mineral oil. The images obtained during the tests indicated a possible degradation of the lubricating oil, resulting in darkening at isolated locations as sliding continued. An increase in the shear rate (sliding speed) resulted in faster degradation of the oil and hence greater susceptibility to early seizure.
EXPERIMENTAL INVESTIGATIONS OF SURFACE WEAR BY DRY SLIDING AND INDUCED DAMAGE OF MEDIUM CARBON STEEL
Diagnostyka, 2021
This study concerns the wear behaviour of metal couples used in industry, particularly in mechanical sliding systems (numerically controlled machine tools). In general, the nature of the materials of the parts of these systems which are in contact and move relatively, are medium carbon steels, thanks to their good mechanical and tribological properties. The present work aims to study, the dry sliding wear of the contact surface of the pin (machine slide) against the contact surface of a disc (machine groove) and the damage induced on the worn track. The pin is AISI 1038 and AISI 1045 steel, the disc is AISI 1055 steel. The tribological tests were carried out on a pin-disc tribometer, in an atmospheric environment. The wear of the pins being evaluated by weighing and studied according to the hardness of the pin with the variation of the normal load applied. The discussion of the results is based on SEM observations and EDS analyzes of worn surfaces and interfacial phenomena produced by dynamic contact. The results obtained indicated the influence of the applied load and the hardness on the wear of the pin and therefore on the tribological behaviour of the worn surfaces.
Failure Investigation: in Flight Loss of a Main Landing Gear Door of a Transport Aircraft
Procedia Structural Integrity, 2017
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
A CRITICAL REVIEW ON DIFFERENT TYPES OF WEAR OF MATERIALS
Many mechanical equipments are subjected to sliding contact in real time applications. Pumps, valves, belt drives, bearings, machinery guide ways, piston- cylinder arrangements etc. are the few important sliding components which are continuously subjected to sliding wear. Much mechanical equipment’s failure occurred due to wear related problems. Therefore, understanding of different wear mechanism is important to design the mechanical components. In this paper, various wear mechanisms have been discussed with the help previous published research works and text books.
In nuclear power plants, tubes and guides of the rod cluster control assemblies undergo impacts at low contact pressures, which lead to a specific wear of the contact surfaces. The aim of this paper is to propose a first explanation of this particular wear with the help of finite element simulations and experimental observations. In a first part, we present some experimental observations, obtained using a tribometer specially designed for this application by AREVA NP, which allows to reproduce the wear scars in the same environment and with equivalent loading conditions. In a second part, we detail the numerical model. More specifically, we consider that the impact-sliding process can be modelled by a scratching process of a double-layered material (stainless steel recovered by a friction film) with a rigid spherical asperity. The mechanical behaviour of these materials comes from instrumented nanoidentation tests and the geometric parameters are deduced from experimental observations. From both the numerical results and the experimental observations, a wear mechanism is then proposed. Finally, we conclude on the capability of finite element analysis to improve the understanding of specific wear phenomena when it is combined to experimental results.
Evaluation of the material’s damage in gas turbine rotors by instrumented spher.PDF
Experimental indentations are carried out on items of two different materials, taken in several location of various components from high pressure gas turbine rotor which have seen an extensive service. The components object of investigation consisted in 1 st and 2 nd high pressure turbine wheels made in nickel-base superalloy (Inconel 718), the spacer ring (Inconel 718) and the compressor shaft made in CrMoV low alloy steel (ASTM A471 type10). Aim of the work is to set up the capability of the instrumented spherical indentation testing system to evaluate variations in the material properties due to damage, resulting from temperature field and stresses acting on components during service. To perform this task load-indentation depth curves will be acquired in various zones of the above mentioned components. The analysis of the results has allowed to identify an energy parameter which shows a linear evolution with the mean temperature acting on the components.