Browsing by Author "Irisarri, A. M."
Now showing 1 - 20 of 31
Results Per Page
Sort Options
Item Creep failure mechanisms of a Ti-6Al-4V thick plate(2001-11) Seco, F. J.; Irisarri, A. M.; Tecnalia Research & InnovationThe creep failure operating mechanisms of a 17-mm thick plate of a Ti-6Al-4V alloy in various heat treating conditions have been investigated. Specimens in the as-received, mill-annealed, condition (50 min maintenance at 720°C and air cooled as the final step of the thermomechanical process) showed the lowest creep resistance and their metallographic analysis revealed that the temperature-activated dislocation climb was the mechanism responsible for the failure and that observed holes were generated by plastic deformation, rather than by creep cavitation. Conversely, maximum times to failure were recorded in beta-annealed specimens (1030°C for 30 min, air cooled and aged for 2 h at 730°C). The fracture surfaces of these broken specimens exhibited an intergranular morphology that was attributed to grain boundary sliding along the former beta grains. Finally, alpha-beta field-annealed samples (940°C 4 h, and furnace cooled at 700°C) possessed intermediate lives between those of mill-annealed and beta-annealed specimens and the failure operating mechanism was diffusional creep by the nucleation and coalescence of the creep cavities generated at the alpha-beta interfaces and the triple points.Item Efecto de la microestructura sobre las propiedades mecanicas y la topografia de la fractura en una aleacion Ti-6Al-4V(1988-11) Azkarate, I.; Gil-Negrete, A.; Irisarri, A. M.; Tecnalia Research & Innovation; Centros PRE-FUSION TECNALIA - (FORMER)The effect of the change in microstructure produced by means of different heat treatments on mechanical properties and fracture topography of a Ti-6Al-4V alloy has been studied. It has been demonstrated that an acicular microstructure produces a loss of ductility independently of its morphology. However, this morology has a strong influence on toughness. The coarse acicular microstructure obtained by air cooling from the β phase shows the highest toughness. However, the fine needles of α′ martensite produced by water quenching from the β phase have the lowest values. The different fracture mechanisms and the crack growth path tortuosity justify this change in behaviour.Item Effect of microstructure on fatigue behaviour of cast Al-7Si-Mg alloy(2001) Atxaga, G.; Pelayo, A.; Irisarri, A. M.; EXTREMAT; Tecnalia Research & InnovationThe fatigue behaviour of a cast Al-7Si-Mg alloy, conforming to A356, has been studied. Specimens of this material were tested in both the as cast condition and a solution treated and aged condition. It was observed that the size, number, and position of casting defects influenced the fatigue life very strongly. This marked effect nearly hides that of the heat treatment. Nevertheless, if the analysis is carried out considering only results obtained from sound specimens it is revealed that the heat treatment causes an improvement in the fatigue resistance of the alloy.Item Effect of microstructure on fracture toughness of Ti-6Al-6V-2Sn alloy(1989) Plaza, L. M.; Azkarate, I.; Gil-Negrete, A.; Irisarri, A. M.; Tecnalia Research & Innovation; Centros PRE-FUSION TECNALIA - (FORMER)The important effects of heat treatment on microstructure, mechanical properties and fractographic facets of a Ti-6A1-6v-2Sn alloy are presented, Beta phase annealing leads to a decrease in the ductility of the alloy independently of the morphology of the acicular microstructure produced. The alpha-beta annealed samples exhibit a higher toughness compared with the original mill annealed condition, reaching, after 4 hours at 900°C a similar level to beta heat treated and air cooled specimens. The very slight decrease in ductility of these samples makes this treatment very promising.Item Effect of the testing temperature on the fracture toughness of a duplex stainless steel(1991-07) Erauzkin, E.; Irisarri, A. M.; Tecnalia Research & InnovationItem Electron beam welded high thickness Ti6Al4V plates using filler metal of similar and different composition to the base plate(2001-06-15) Barreda, J. L.; Santamaría, F.; Azpiroz, X.; Irisarri, A. M.; Varona, J. M.; EXTREMAT; Tecnalia Research & InnovationCompositional changes of the welds carried out by the electron beam welding process have been investigated in the present work. Addition of a filler metal in the weld fusion zone has been used to solve some problems by improving the behaviour of the joint by minimising either the porosity, the notching or the cracking susceptibility of the joint (Sanderson et al., Met. Constr. Br. Weld. J. (1972); Atsuta et al. 3er CISFFEL, Lion, Francia, September 1983; Nazarenko and Kaidalov, Technological procedures of electron beam welding and repair; Murphy and Turner, Weld. J. (1976)). Filler metal can also be used to weld high thickness plates by low-power electron beam welders (Ruge and Oestmann et al., Decker. Electron and Laser Beam Welding, 11W, 1976). The main purpose of this work is to investigate the behaviour of a 17 mm Ti6Al4V weld by the electron beam welding process with a filler metal of similar and dissimilar composition to the base plate. In the present work the initial results of 17 mm thickness Ti6Al4V plates welded with a 3kWEB welder and a filler metal of titanium alloy of the same and different composition to the base metal are presented.Item Estado actual de la tecnologia de solidificacion rapida. I Parte Caracteristicas de los productos y procesos de fabricacion(1989-01) Gutierrez, M.; Irisarri, A. M.; Froes, F. H.; Tecnalia Research & InnovationInterest towards Rapid Solidification (RS) of products has greatly increased during past years. Main reasons are both good properties obtained by means of high cooling rates and the development of new materials which cannot be produced by any conventional method. This report first describes the structural characteristics of metals obtained through rapid cooling and the present manufacturing processes. The second part analyzes applications of both crystalline and amorphous materials achieved by RS. At the same time, applications of products obtained directly from RS processes without further steps are also reviewed.Item Estado actual de la tecnologia de solidificacion rapida. II Parte. Materiales cristalinos y amorfos. Aplicaciones(1989-03) Gutierrez, M.; Irisarri, A. M.; Froes, F. H.; Tecnalia Research & InnovationIn Part I of this work, reference was made to the three main rapid solidification processes and to their effects on the metals obtained. Such effects are mainly structure refinement and homogeneity, an increment of solid solubility limits, absence of segregation, and a possibility of formation of new crystalline or amorphous phases. This Part 2 describes applications of these alloys considered either as intemediate products that must be further processed or as final products which need not be subjected to any compacting intermediate process.Item Failure analysis of a set of compressor blades(2008-09) Silveira, E.; Atxaga, G.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationThis paper analyses the root causes of the failure of a set of blades belonging to the high pressure compressor of an aircraft engine. All these blades were manufactured using a 718 nickel base alloy. The performed study consisted in a fractographic analysis by scanning electron microscopy and a microstructural study using both scanning and optical microscopy. Phases which were present in the fracture surfaces were identified by means of X-ray energy dispersive spectrometry. As a result of this labour the failure was attributed to the impact of sand and stones; that is the so-called foreign object damage mechanism.Item Failure analysis of a set of stainless steel disc springs(2006-03) Atxaga, G.; Pelayo, A.; Irisarri, A. M.; EXTREMAT; Tecnalia Research & InnovationThis paper analyses the failure of a set of disc springs, broken in service in a seawater environment and at high temperature. These components were manufactured using a 17-7 PH, UNS S17700 precipitation hardening stainless steel. The morphology of the cracks was intergranular and it was attributed to hydrogen embrittlement due to the hydrogen that entered into the steel during the acid pickling. This hypothesis was confirmed by baking the samples to remove this hydrogen. This action increased significantly the ductility of the steel and modified the morphology of the fractures.Item Failure analysis of an open die forging drop hammer(2009-07) Irisarri, A. M.; Pelayo, A.; Tecnalia Research & InnovationThis paper analyses the failure of a large open die forging drop hammer. The analysis had to be semi-destructive as it was wanted to repair the equipment and to return it into service. A visual examination was performed at the forging shop and fatigue initiated at two internal defects blamed for the failure. A small sample was extracted from the fracture surface. Unfortunately, due to the desire of recovering the drop hammer this sample did not belong to those zones which were identified to be the origins of the failure but to the zone of progression of the crack by fatigue close to the overload final failure. Fractographic analysis by scanning electron microscopy revealed the presence of some ductile dimples pointing to an acceleration of the cracking process at this stage.Item Failure analysis of the end of a shaft of an engine(2010-06) Atxaga, G.; Irisarri, A. M.; EXTREMAT; Tecnalia Research & InnovationThe aim of this paper is to analyse the root causes of the premature failure of the end of the shaft of an engine, which was theoretically manufactured using a C45 steel. This shaft presented a keyway which was damaged and repaired by welding, machining a new one in another zone of its periphery. Neither the carbon content nor the mechanical properties of the steel agreed with those specified in the purchase order, having strength significantly lower than the envisaged one. Examination of the fracture surface revealed that the origin of the failure was sited in one corner y of the first keyway which was incorrectly repaired. From this origin, cracking progressed by fatigue until the area which remained joined was not enough for bearing the applied loading, inducing the failure. The marked damage suffered by the fracture surface precluded evaluating the existing ratio between fatigue crack growth and final fracture and determining if the stress level was high. Observation of the metallographic samples confirmed the deficient union between the key used for repairing the previous damage and the shaft promoting a faster cracking. Consequently, the failure of the shaft was attributed to the sum of various factors (lack of strength, incorrect design and execution of the repair) which have promoted the failure.Item Failure analysis of two sets of aircraft blades(2008) Silveira, E.; Atxaga, G.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationThis paper analyses the failure of two blades, coming from different aircraft engines. The first one corresponds to the high pressure compressor manufactured in a 718 nickel base superalloy. The failure analysis carried out on this blade points towards foreign object damage (FOD). The second set belongs to the high pressure turbine of another engine. Scanning electron microscopy attributes the first fail to the premature failure by a thermo-mechanical fatigue mechanism of one blade with an inadequate microstructure. The remaining blades of this set, which possess a correct microstructure, failed due to the impacts of the debris generated by the fracture of the first one.Item Failure analysis of two sets of aircraft blades(2010-04) Silveira, E.; Atxaga, G.; Irisarri, A. M.; Caracterización y Validación. Materiales; EXTREMAT; Tecnalia Research & InnovationThis paper describes the methodology employed for the failure analysis of aircraft blades and its application to two premature failed sets. The first one corresponds to the high pressure compressor manufactured in a 718 nickel base superalloy. The failure analysis carried out on this blade points towards foreign object damage (FOD). The second set belongs to the high pressure turbine of another engine. Scanning electron microscopy attributes the first fail to the premature failure by a thermo-mechanical fatigue mechanism of one blade with an inadequate microstructure. The remaining blades of this set, which possess a correct microstructure, failed due to the impacts of the debris generated by the fracture of the first one.Item Fragilizacion por hidrogeno de tubos de acero API 5LX-52 y X-60(1988-09) Azkarate, I.; Erauzkin, E.; Pelayo, A.; Irisarri, A. M.; Tecnalia Research & InnovationThe behavior of API 5LX-52 and X-60 pipe line steels was studied under two hydrogen embrittlement conditions, these were hydrogen embrittlement itself and hydrogen assisted stress cracking. Determination of the Embrittlement Index was performed to study the first case and no sensitivity to this phenomena was found in either material. Nevertheless, an important loss of ductility was shown by both steels in the second case. This was studied by means of the slow strain rate technique with different hydrogen evolutions (produced by different cathodic potentials) at the specimen surface during the test.Item Improvement of the corrosion behaviour of construction steels(1998) Penalba, F.; Azkarate, I.; Irisarri, A. M.; Izaga, J.; del Barrio, A.; Tecnalia Research & Innovation; MATERIALES PARA CONDICIONES EXTREMASThe improvement of the corrosion behaviour of construction steels has been analyzed. This study followed two different lines. Firstly, the corrosion behaviour of steel directly exposed, unpainted, to the atmosphere is discussed. Weathering steels produced by the introduction of slight modifications in chemical composition and the use of alternating wetting and drying cycles exhibit a corrosion resistance that is up to eight times better than that of plain carbon steels. Moreover, the mechanical strength of these steels is higher, allowing a significant weight saving. Secondly, the protection of the steel by means of paints is considered. The use of metallic and organic coatings to protect the steel from the corrosive environment is discussed. The combination of both metallic and organic coatings that is very often used in order to provide a long term corrosion protection for steel used in building purposes has been studied by outer exposure of the samples to a marine environment. Best results were obtained by using a strontium chromate primer. A very marked influence of the inclination of these samples on the corrosion performance was observed. Those samples which have a lower inclination are corroded more easily probably due to the more difficult drainage of the rain compared to those with a higher slope, allowing its corrosive attack for a longer time.Item Improvement of Ti6Al4V fracture toughness by sub-transus heat treatment(1990-09) Plaza, L. M.; Irisarri, A. M.; Gil-Negrete, A.; Tecnalia Research & Innovation; Centros PRE-FUSION TECNALIA - (FORMER)Item Influence of microstructure on fracture toughness and corrosion embrittlement of a duplex stainless steel(1996) Irisarri, A. M.; Erauzkin, E.; Tecnalia Research & InnovationThe influence of microstructural changes induced by means of different heat treatments on fracture toughness and sulphide stress corrosion cracking in a duplex stainless steel has been studied. Heat treatment at 825°C induced the precipitation of sigma phase after a period as short as 5 minutes. The effect of this sigma phase on fracture and corrosion behaviour is dramatic. As much as 95% of the initial toughness was lost after a period of maintenance of only 2 hours and the sulphide stress corrosion test specimens failed after a very short time. Specimens treated at 675°C for a short time exhibited a microstructure constituted by carbides but no sign of any intermetallic compound was observed. These carbides induced a loss of toughness less marked than that found in 825°C samples and the corrosion specimens passed the tests. More prolonged exposures induced the presence of intermetallic phases leading to a further decrease in toughness and the failure of the corrosion specimens. SEM examination helps to explain this behaviour.Item Influence of the filler metal on the mechanical properties of Ti-6Al-4V electron beam weldments(2010-07-23) Barreda, J. L.; Azpiroz, X.; Irisarri, A. M.; EXTREMAT; Tecnalia Research & InnovationThe influence of various filler metals on the mechanical properties of 17 mm thick Ti-6Al-4V electron beam welded joints has been analysed. Autogeneous welded joints exhibit higher toughness when compared to the parent plate but this improvement was less marked than that observed in plasma arc welded joints. To achieve better toughness, without suffering unacceptable losses of strength, different morphologies of commercially pure titanium filler metals have been employed. Using 0.50 mm thick sheet as filler metal leaded to maximum toughness but as counterpart a significant decrease in strength was observed. To obtain high toughness while maintaining a high strength level 0.25 mm sheet and 1 mm diameter filler metals are recommended. Fractographic examination of the failed specimens helped to explain the fracture behaviour of the different welded joints.Item Influence of the filler metal on the properties of Ti-6Al-4V electron beam weldments. Part I: Welding procedures and microstructural characterization(2009-11-05) Irisarri, A. M.; Barreda, J. L.; Azpiroz, X.; Tecnalia Research & Innovation; EXTREMATThe use of different procedures for electron beam welding of 17 mm thick Ti-6Al-4V plate and the difficulties found in this process are analysed. When this alloy was welded autogeneously the presence of significant amounts of α martensite was observed, recommending looking for another solution. In the early trials a V joint design was used but distortions and defects were detected in the welds when multi-pass procedures were considered. Consequently, for the remaining weldments K or I joint configurations were selected. Initially, Ti-6Al-4V wire was preferred in order to match mechanical properties with base material but no significant improvement was found leading to consideration of using a less alloyed filler metal. Different commercially pure titanium filler metals have been employed to optimise the performance of the fusion zone of electron beam weldments. In a second paper [1] the influence of the welding procedure on the mechanical properties of the various joints will be discussed.