Scanning Auger Microprobe Analysis Research Articles

Structure and surface of TiNi human implants

The surface and the “bulk” structure of TiNi implants were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS), and scanning Auger microprobe analysis (AES). TiNi implants were compared with otherwise identically prepared non-implanted specimens, and sputter-cleaned and reoxidized samples. Non-implanted and implanted samples had essentially the same surface topography and microstructure. Ti, O, and C were the dominant elements detected on the surface. Trace amounts (∼1 at%) of Ni and Ca, N, Si, B, and S were also detected. Ti was present as TiO 2 on the surface, while nickel was present in metallic form. A significant difference in Ni peak intensity was observed when retrieved or non-implanted control samples (a very low nickel content) were compared with sputter-cleaned and reoxidized samples (well-detected nickel). It is evident that the method of passivation is crucial for nickel loosening. No major changes occurred in the TiNi samples bulk structure or in the surface oxide during the implantation periods investigated.

Neutron irradiation and intergranular fracture in vanadium-20 wt% titanium alloys undoped and doped with phosphorus and sulfur

The mechanical properties and grain boundary composition affected by neutron irradiation (9.8 × 10 24 n/m 2: E > 0.1 MeV at 438°C) in undoped, P-doped and S-doped V-20wt% Ti alloys all containing residual C and O have been studied using a small punch testing method and scanning Auger microprobe analysis. Neutron irradiation facilitated heterogeneous formation of intergranular microcracks, not leading to specimen failure, in all undoped and some-S-doped specimens. An irradiated undoped alloy indicated ductility loss to a smaller extent than expected from the easy microcracking due to a mixture of intergranular and transgranular macrocracking. The irradiation effect on the ductility varied in the S-doped alloy, while the irradiation exerted a beneficial effect on low temperature ductility in P-doped alloys. Intergranular S segregation in the undoped alloy and S desegregation in the S-doped alloy occurred during the irradiation. Unirradiated and irradiated P-doped alloys exhibited negligible S segregation and much smaller P segregation than the S segregation in the undoped and S-doped alloys. The grain boundary content of C affecting the ductility was remarkably reduced in the irradiated P-doped alloy and S-doped specimens with ductility loss. The ductility loss and improvement observed in the irradiated alloys are interpreted in light of the variations in segregation and precipitated impurities together with hardening behavior.

High temperature environmental attack and mechanical degradation of coatings in gas turbine blades

This paper examines how in-service and thermal environmental attack influence the mechanical properties (22–950°C) of CoNiCrAlY coatings over René 80 substrates in gas turbine blades using a small punch (SP) testing technique in conjunction with scanning Auger microprobe analysis. SP tests have clearly demonstrated strong dependence of mechanical degradation of near surface coatings on the elevated temperature environmental condition. The room temperature (RT) ductility in blade coatings decreased with increasing operating time under combined fuels of kerosene and liquefied natural gas (LNG) despite softening in used coatings. All the coatings depicted lower ductility at 825°C in air than at RT but not in vacuum so that the oxidizing environment would produce deleterious effects. In-service operation under the combined fuels led to a two-fold increase in the ductile—brittle transition temperature (DBTT) over coatings observed under mainly LNG because of more extensive oxidation and grain boundary sulfidation. However, the DBTT of coating did not change during thermal ageing at 870°C in air that produced only oxidation. These findings imply that the grain boundary sulfidation would exert a stronger embrittling effect on the CoNiCiAlY coatings than the oxidation.

Examination of In-Service Coating Degradation in Gas Turbine Blades Using a Small Punch Testing Method

AbstractThis paper describes examination of in-service coating degradation in land based gasturbine blades by means of a small punch testing (SP) method and scanning Auger microprobe(SAM). SP tests on coated specimens with unpolished surfaces indicated large variations ofthe mechanical properties because of the surface roughness and curvature in gas turbine blades, SP tests on polished specimens better characterized the mechanical degradation of bladecoatings. The coated specimens greatly softened and the room temperature ductility of thecoatings and substrates tended to decrease with increasing operation time. The ductile-brittletransition temperature of the coatings shifted to higher temperatures during the bladeoperation. From SAM analyses on fracture surfaces of unused and used blades, it has beenshown that oxidation and sulfidation near the coating surface, which control the fractureproperties, result from high temperature environmental attack.

Degradation Characteristics of Intermetallic Coating on Nickel Base Superalloy Substrate in Gas Ttairbine Blade

Abstract In-service degradation of the mechanical properties (295-1223 K) and microstructure/chemistry in gas turbine blades made of CoNiCrAlY coatings and Rene 80 substrates has been studied by means of a small punch (SP) testing technique and scanning Auger microprobe (SAM). In SP tests, brittle coating cracks continuously and discretely propagated along the radial and tangential directions at 295 K and elevated temperatures, respectively. The ductility of the coating and substrate at 295 K was lowered during long time operation of the blades. The ductile-brittle transition temperature of used coatings was increased by 90 K, compared with that of unused ones while that of the substrate remained unchanged. From SAM analyses of the unused and used blades, it was found that oxidation and S segregation near the coating surface region profoundly occur in-service. The relationship between the mechanical property degradation and microstructural/chemical evolution near the coating surface is presented which serves as a data base for determining the remaining life of gas turbine blades.

Synchrotron radiation photoemission and scanning Auger microprobe study of hydrated silica

Synchrotron radiation photoemission and scanning Auger microprobe analysis are used to study the surface chemical composition of hydrated silica. Si-OH species produced a high-binding energy peak in photoemission spectra when Si2p electrons possess the same attenuation length of SiLVV electrons. Conversely, no spectral change is observed in SiLVV, OKVV, and SiKLL regions relative to the case of anhydrous silica. The presence of silanol species is evidenced by the I OKVV/ I SiLVV intensity ratio which is meaningfully higher in hydrated silica than in anhydrous silica, and this ratio varies laterally up to nearly 50% as a function of position on the surface. On the contrary, the I OKVV/ I SiKLL is virtually equal to the value of anhydrous silica, and shows no appreciable lateral dishomogeneity. The diagnostical capabilities of photoemission and Auger techniques in detecting chemical changes in silica are discussed on the grounds of: (i) the chemical shift, (ii) the experimental band width and, (iii) the electron attenuation length associated with a particular spectral transition.

Observations of segregation and grain-boundary faceting by tellurium and oxygen in iron

Tellurium is known to be a highly surface-active impurity in iron and to cause severe intergranular embrittlement and grain-boundary faceting. In this regard it behavior of Te-doped iron using high-resolution scanning Auger microprobe analysis of specimens given a variety of heat treatments and fractured in UHV stet, so that a comparison could be made of the two systems. In general, it was found that the appearance of the faceted grain boundaries is similar, but significant differences exist with regard to the temperature dependence. A new and quite unexpected finding was that oxygen can substitute for tellurium on a faceted grain boundary in iron. The implications of this are discussed.

A Scanning Auger Microprobe analysis of the oxidation of a Zr 2Ni alloy

A Scanning Auger Microprobe (SAM) was used to investigate the chemical structure of oxides formed on Zr 2Ni and ZrNi. The information was used to explain the catastrophic oxidation behaviour of a Zr 2Ni alloy containing small ZrNi precipitates and, in general, indicated the important role that second-phase particles occupy in phenomena such as corrosion.

The effect of hydrogen on the strength and ductility of V-15at.%Cr-5at.%Ti

Abstract The effect of hydrogen in solid solution on the strength and ductility of a V-15at.%Cr-5at.%Ti alloy was investigated from 78 to 450 K. The non-hydrogenated alloy exhibited a ductile-to-brittle transition at a low temperature (210 K) which scanning Auger microprobe analyses indicated was due to segregation of sulfur and titanium to the grain boundaries. The addition of only 0.1 at.% H raised the ductile-to-brittle transition temperature above room temperature. Hydrogen produced little, if any, strengthening in this alloy. A comparison of hydrogen effects on ductility and strengthening between this alloy and V-20at.%Ti and V-20at.%Cr is presented.

Characterization of CdTe polycrystalline films by x-ray photoelectron and Auger spectroscopies

Using x-ray photoelectron spectroscopy (XPS) and scanning Auger microprobe (SAM) techniques we have studied the stoichiometry and contamination of CdTe polycrystalline films grown by the hot wall close-spaced vapor transport technique. XPS and SAM analyses show that the density of impurities in the bulk of the films is <1018 cm−3. Cross sections of the CdTe films perpendicular to the surface–glass interface were exposed by cleaving in vacuum. SAM measurements on these surfaces show that small concentrations of C impurities appear on some regions and some others present only Cd and Te. Thus, we intend to show that films produced with this technique are reasonably free of bulk contamination.

Reactive Ion Etching of Aluminum/Silicon in BBr3 / Cl2 and BCl3 / Cl2 Mixtures

Boron tribromide mixed with chlorine, , a novel gas mixture for dry etching of Al and Al alloys, has been studied in a hexagonal cathode reactive ion etching system. Etch rates, selectivities, profiles, and linewidth loss were determined as a function of feed gas composition, dc self‐bias, and reactor load in a Box‐Behnken experimental design. Response surface analysis indicates a window exists in the experimental parameter space where significant improvements in selectivity can be achieved without sacrificing anisotropic profiles. For example, anisotropic etching can be achieved with mixtures while maintaining and Al/photoresist etch rate ratios of 33:1 and 15:1, respectively. The achievable selectivities in a conventional mixture of were 13:1 and 2.5:1 for comparable anisotropic etching. Optical emission and mass spectrometry measurements were used to aid in an investigation of the kinetics of etching of Al and films. Scanning Auger microprobe analysis was performed on the postetched substrates. A kinetic model is proposed to account for variations between and RIE etching of Al and Al alloys.

Growth Kinetics of Palladium Silicides Formed by Rapid Thermal Annealing

Palladium silicide is formed through contact reaction of an electron‐deposited Pd thin film and single‐crystal <100> Si substrate by rapid thermal annealing (RTA). The sample temperatures are carefully measured by both optical pyrometer and thermocouples. The annealed samples are analyzed by four‐point probe measurements, x‐ray diffraction (XRD), scanning electron microscopy (SEM), and scanning Auger microprobe analysis (SAM). is the first and only phase detected in the temperature range 310°–460°C. The temperature at which starts to form is 320°C, and the activation energy for the diffusion‐controlled silicide growth is found to be . These results show that the growth mechanism of is the same in both rapid thermal annealing and conventional furnace annealing.

Gettering of Carbon and Oxygen in Silicon Processing

The control of carbon and oxygen is of great importance in today's silicon materials and device processing, and it will become a critical parameter in the immediate future for VLSI device processing. Although considerable technology and some understanding are available today in the control of oxygen in silicon materials through processing, there is little technology and even less understanding of carbon control in silicon wafer processing. We have determined, for high carbon content silicon, that carbon can be gettered to damage sites such as dislocations, stacking faults, and/or wafer surfaces, thus creating a carbon‐denuded zone in epitaxial silicon, as well as in bulk Czochralski silicon substrates. The gettering effects of carbon have been investigated using controlled time, temperature, and ambient gas thermal anneals. The characterization of these materials was carried out using chemical etches, Fourier transform infrared spectroscopy, and scanning Auger microprobe analysis.

The effect of electrolyte composition on the cathodic reduction of CuFeS 2

The electrochemical reduction of CuFeS 2 mineral electrodes has been investigated by performing cathodic polarization curves, constant potential experiments, and cyclic polarization curves in various electrolytes. The effects of H 2SO 4, Fe 2+ and Cu 2+ concentrations have been examined as well as the effects of various dissolved gases, air, O 2, H 2S and N 2. Decreasing H 2SO 4 only shifts the curve to more negative potentials but initial concentrations of 0.36 M Fe 2+ cause up to a ten-fold enhancement in the observed current. The presence of oxygen or Cu 2+ also leads to an increase in the reduction current but in either case further increases in current are observed when Fe 2+ is added to the electrolyte. Chalcocite (Cu 2S) or djurleite (Cu 1.96S) have been identified as products of reaction, although it is possible that a thin layer of a different copper-iron sulfide may form as an intermediate based on the color changes which appear after cathodic excursions. In addition, scanning Auger microprobe analyses of these surfaces show an increasing Cu:Fe ratio as the time at potential is increased. The results also indicate that the solid product layer is porous. A mechanism which accounts for the observed current increase in the presence of Fe 2+ is proposed which involves a redox reaction between dissolved Fe 2+ and cupric ion in the copper sulfide product layer.

Effect of nitrogen on the crystal texture and microstructure of sputtered Ni-Fe films

This work reports the effect of nitrogen in the sputtering gas on the crystal texture and microstructure of 1 μ thick 81/19 Ni–Fe films sputter deposited on silica glass and silicon. X-ray diffraction, transmission electron microscopy, and scanning auger microprobe analysis have been used to characterize films’ properties. The films show (111) and (002) crystals orientations. Upon increasing the nitrogen content of the sputtering gas, the amount of (111) crystal texture decreases; whereas the amount of (002) crystal texture shows a maxima at about 0.1% nitrogen. The microstructural analysis of films shows that the presence of nitrogen in the sputtering gas promotes fine grain size. The mechanism of crystal texture development with an increase in the amount of nitrogen in the sputtering gas is discussed.

Film growth characterization of an underlayer for perpendicular magnetic recording

This investigation involves a study of the dependence of the crystal texture of sputtered Ni-Fe films on film thickness and the oxygen content of the sputtering gas. X-ray diffraction, analytical transmission electron microscopy, and scanning auger microprobe analysis have been employed to characterize the films. The

Effects of Chromium Additions and Flux Type on the Structure and Properties of HSLA Steel Submerged Arc Weld Metal

The effects of chromium additions on the microstructures and properties of submerged arc welded HSLA steels were examined using two different fluxes: a basic agglomerated flux and a recently developed flux designed to deposit titanium and boron.Instrumented impact tests were done on pre-fatigued Charpy specimens. These indicated that the titanium-boron flux was very beneficial to toughness, compared to the conventional flux. Metallographic examination showed that the major reasons for this were: (1) attainment of a 100 % acicular ferrite microstructure; (2) avoidance of the embrittlement of austenite grain boundaries which was found in all of the welds made using the conventional flux; (3) an increase in the upper shelf energy despite similar oxygen contents and (for a given Cr level) similar tensile properties and microhardness. Scanning Auger microprobe analysis showed segregation of P, C, N, Mo and Cr to brittle grain boundaries.Chromium additions were generally detrimental to toughness in both weld series. This decrease in toughness corresponded to a general increase in hardenability, indicated by microhardness and ultimate tensile strength, and by a deterioration of the microstructures, namely, increases in the fractions of martensite-austenite (M-A) and bainite phases.

Effects of Chromium Additions and Flux Type on the Structure and Properties of HSLA Steel Submerged Arc Weld Metal

The effects of chromium additions on the microstructures and properties of submerged arc welded HSLA steels were examined using two different fluxes: a basic agglomerated flux and a recently developed flux designed to deposit titanium and boron.Instrumented impact tests were done on pre-fatigued Charpy specimens. These indicated that the titanium-boron flux was very beneficial to toughness, compared to the conventional flux. Metallographic examination showed that the major reasons for this were: (1) attainment of a 100 % acicular ferrite microstructure; (2) avoidance of the embrittlement of austenite grain boundaries which was found in all of the welds made using the conventional flux; (3) an increase in the upper shelf energy despite similar oxygen contents and (for a given Cr level) similar tensile properties and microhardness. Scanning Auger microprobe analysis showed segregation of P, C, N, Mo and Cr to brittle grain boundaries.Chromium additions were generally detrimental to toughness in both weld series. This decrease in toughness corresponded to a general increase in hardenability, indicated by microhardness and ultimate tensile strength, and by a deterioration of the microstructures, namely, increases in the fractions of martensite-austenite (M-A) and bainite phases.

Anisotropie embrittlement in high-hardness ESR 4340 steel forgings

ESR 4340 steel forgings tempered to a hardness of HRC 55 exhibit a severe loss of tensile ductility in the short transverse direction which is strain-rate and humidity dependent. The anisotropy is also reflected in blunt-notch Charpy impact energy, but is absent in the sharp-crack fracture toughness. Brittle behavior is associated with regions of smooth intergranular fracture which are aligned with microstructural banding. Scanning Auger microprobe analysis indicates some intergranular segregation of phosphorus and sulfur in these regions. The anisotropic embrittlement is attributed to an interaction of nonequilibrium segregation on solidification with local equilibrium segregation at grain boundaries during austenitizing. This produces defective regions of enhanced intergranular impurity segregation which are oriented during forging. The regions are prone to brittle fracture under impact conditions and abnormal sensitivity to environmental attack during low strain-rate deformation. A relatively sparse distribution of these defects (∼10cm−3) accounts for the discrepancy between smooth bar and blunt-notch testsvs sharp-crack tests. Isotropie properties are restored by homogenization treatment. For application of these steels at extreme hardness levels, homogenization treatment is essential.

The effect of additives on the eutectoid transformation of ductile iron

The eutectoid transformation of austenite in cast iron is known to proceed by both the meta-stable γ → α + Fe3C reaction common in Fe-C alloys of near eutectoid composition, and by the direct γ → α + Graphite reaction, with the graphite phase functioning as a car-bon sink. In addition, the meta-stable cementite constituent of the pearlite can dissolve near the graphite phase (Fe3C → α + Graphite), producing free ferrite. Isothermal trans-formation studies on a typical ductile iron (nodular cast iron) confirmed that all of these reaction mechanisms are normally operative. The addition of 1.3 pct Mn was found to substantially retard all stages of the transformation by retarding the onset of the eutectoid transformation, decreasing the diffusivity of carbon in ferrite, and stabilizing the cemen-tite. Minor additions of Sb (0.08 pct) or Sn (0.12 pct) were found to inhibit the γ →α + Graphite reaction path, as well as the Fe3C → α + Graphite dissolution step, but did not significantly affect the meta-stable γ → α + Fe3C reaction. Scanning Auger microprobe analysis indicated that Sn and Sb adsorb at the nodule/metal interphase boundaries during solidification. This adsorbed layer acts as a barrier to the carbon flow necessary for the direct γ → α + Graphite and Fe3C → α + Graphite reactions. With the graphite phase dis-abled as a sink for the excess carbon, the metal transforms like a nongraphitic steel. The effects of Mn, Sn, and Sb on the eutectoid transformation of ductile iron were shown to be consistent with their behavior in malleable iron.