D.J. Child

Loughborough University | Lough · Loughborough Materials Characterisation Centre

Two new alloy compositions for possible disk rotor applications have been examined. Both were intended to have higher γ′ content than the existing alloy, RR1000, and be produced using powder metallurgy and isothermal forging to enable forgings to show a consistent coarse grain microstructure. Small pancake forgings of the new alloys and RR1000 were...

Two new alloy compositions for possible disk rotor applications have been examined. Both were intended to have higher γ′ content than the existing alloy, RR1000, and be produced using powder metallurgyPowder metallurgy and isothermal forging to enable forgings to show a consistent coarse grain microstructure. Small pancake forgings of the new alloy...

This work investigates coarsening behavior of strengthening precipitates (g') in coarse-grained RR1000 after isothermal exposure for various times (50 to 500 hours) at 700°C and 750°C. The impact of these isothermal treatments is then studied by carrying out dwell (1 hour) fatigue crack growth tests at 700°C in air. Such dwell periods can increase...

The influence of sulfur contamination on the corrosion-fatigue behavior of a polycrystalline superalloy used in aero-engines is considered. Samples tested under a variety of environmental conditions (including exposures to air, SOx gas, and salt) are characterized through a suite of high-resolution characterization methods, including transmission e...

The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 an...

Samples of RR1000 with differing grain size and surface finish have been exposed to air at different pressures. Specimens were exposed for 4000 h at 650°C with some exposed to atmospheric pressure air and some exposed to air at 40 bar pressure. Samples exposed to elevated pressure formed a surface layer of NiCr2O4 whereas that formed on samples tes...

Shot peening (SP) has been widely used to improve fatigue performance by inducing compressive residual stresses and strain hardening in materials. However, the beneficial effect of shot peening may partially disappear under high temperature operating conditions of aero-engine components. In the current study, the microstructure and material propert...

Currently there is doubt surrounding the suitability of chemically-induced stress independent pre-conditioning of specimens to simulate turbine corrosion prior to fatigue testing. The thick oxide scales developed using such techniques can lead to net section loss and typically a lack of grain boundary sulphide attack seen in components that experie...

Operation of gas turbines at high temperatures can lead to corrosion of turbine materials. A programme was designed to understand the corrosion-fatigue behaviour of two grain size variants of RR1000 under cyclic loading at elevated. Tests were conducted on cylindrical specimens under a range of loading conditions. Results indicated that salted spec...

Cylindrical bars of the advanced nickel based superalloy RR1000 were subjected to swaging to induce approximately 30% cold work. Grain size analysis demonstrated a distinct modification to the microstructure whilst electron back scattered diffraction (EBSD) measurements confirmed the evolution of a relatively strong <111> texture parallel with the...

A prototype next-generation superalloy containing 1 at.% Mn was oxidised in air at 800 °C for 100 h, and compared with a commercial Ni-based superalloy. The oxide scale consisted of a multi-phase layered structure measured by Atom Probe Tomography as uppermost NiCr 2 Mn 2 O 4 , followed by an inhomogeneous mix of Cr 2 O 3 , spinel MnCr 2 O 4 and ru...

The low cycle fatigue performance of the nickel based superalloy RR1000 was investigated under a variety of load waveforms at high temperature, employing a double edge notch geometry under load control. Experiments on a plain cylindrical specimen design under strain control were later performed to simulate the constrained conditions at the root of...

The effects of prior oxidation on the room temperature fatigue life of coarse-grained Ni-based superalloy, RR1000, have been investigated. High cycle fatigue tests were conducted, on both machined and pre-oxidised testpieces, at room temperature at an R ratio of 0.1. The oxidation damage was produced by pre-exposures at 700 °C for either 100 or 200...

The effect of shot-peening on the oxidation in air of the Ni-based superalloy RR1000 has been investigated over the temperature range 700-800°C. The surface oxide in both peened and un-peened conditions consisted of isolated grains of rutile on the outermost surface beneath which was a protective Ti-doped chromia scale. Internal oxidation of alumin...

The effect of prior oxidation on the room temperature fatigue life of coarse grained Ni based superalloy, RR1000 has been performed at an R ratio of 0·1 with two pre-oxidation times: 100 and 2000 h at 700°C. These pre-exposures produce extensive oxidation damage. The room temperature high cycle fatigue life of the pre-oxidised specimens has been co...

Isothermal oxidation of the Ni based superalloy, RR1000, has been performed at 700, 750 and 800°C for exposure periods up to 2000 h. A chromia external oxide scale with an outer layer of rutile was formed together with extensive internal oxidation of aluminium, both intragranularly and intergranularly. The internal oxidation was associated with a d...

The current demands of the aviation industry for increased gas-turbine efficiency necessitate higher turbine entry temperatures, requiring that alloys exhibit superior oxidation resistance. The synergistic effects of oxidation and mechanical stresses pose a complex issue. The purpose of the current research was to examine the effects of stress on t...

Minimum dwell fatigue testing of nickel based superalloy FG RR1000 at 650 °C has led to significant reductions in fatigue life. The reduction in fatigue life under minimum dwell fatigue has been caused by relatively early and multiple crack initiation events from a highly oxidised surface. The depth of oxidation damage, in the present circumstances...

Sustained deflected crack growth is a concern as we need to understand both the factors which cause it and when it may happen in a component to ensure we have appropriate lifing strategies in place. This behaviour has been reported in a number of fine-grained Ni-based turbine disc alloys at intermediate temperatures (200-600C°). Such fracture surfa...

Multiple three-dimensional reconstructions of a γ/γ' phase structure in Alloy 720Li have been carried out by employing a serial milling technique with simultaneous electron backscatter diffraction (EBSD) and energy dispersive x-ray (EDX) analysis data collection. Combining EBSD data with EDX is critical in obtaining maps to distinguish between the...

An electron backscatter diffraction (EBSD)-based tool is described to assess the depth of strain-hardening effects of shot-peening treatments applied to the Ni-based superalloy, Udimet© alloy 720Li. The method consists of a statistical analysis of a number of data points from each grain scanned based on the grain orientation spread and their relati...

of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

An overview of the field of electrically conductive polymers is presented. The synthesis of conducting polymers is discussed with detailed sections describing polyacetylenes, polyphenylenes, polyheterocycles, poly(arylene vinylenes), and polyanilines. The preparations of conducting polymer blends, composites, and colloids are described. The concept...

Polypyrrole (PPy)-coated textile fabrics were prepared with varying surface resistivities and were studied for their gas sensing capabilities by monitoring conductivity changes. Approximately an order of magnitude reversible change in conductivity was observed when these fabrics were sequentially exposed to NH3 and HCl gases. While the change in co...

Polypyrrole can be chemically synthesized in the presence of textiles to yield a conducting textile material where the polypyrrole forms a coherent layer on the textile substrate. The surface resistance of the textile can be controlled by altering the thickness of the polypyrrole coating. The incorporation of aromatic dopants, such as anthraquninon...

The effects of backbone and pendant side-chain structure on the electronic and electrochemical properties of a series of poly[1,4-bis(2-heterocycle)-p-phenylenes] have been studied using a combination of optical spectroscopic, electrochemical, and EPR techniques. The selection of the heterocycle (thiophene or furan) and the nature of the pendant gr...

Spreading, isotherms and polymerization of 2-pentadecylaniline at a planar aqueous electrolyte-organic interface were examined by monitoring the interfacial pressure employing the Wilhelmy-plate method. These results indicate the presence of monomer confined to the interface. Application of a voltage across the interface using stainless steel elect...

In this study, a water-soluble, electroactive, and electrically conductive, sulfonatoalkoxy-substituted poly(p-phenylene), poly[2, 5-bis(3-sulfonatopropoxy)-1,4-pheylene-alt-1,4-phenylene] (PPP-ORSO3), has been synthesized by the homogeneous Suzuki coupling method. The terminal sulfonate functionality induces water solubility to the rigid-rod backb...

The chemical polymerization of pyrrole in the presence of textile substrates results in the formation of electrically conducting, polypyrrole coated fabrics. Applications of these materials include microwave attenuation, static charge dissipation, and EMI shielding. The degradation kinetics of the electrical conductivity of these materials has been...

A series of 1,4-bis(2-furanyl)benzenes, substituted at the 2 and 5 positions of the benzene ring with methyl, methoxy, and heptoxy groups, has been synthesized and electropolymerized. Spin density calculations of monomer radical cations show relatively high spin densities on the external alpha positions of the furan rings. These polymers exhibit co...

A series of polyphenylene derivative polymers with a variety of heterocyclic units along the main chain, and various pendant groups, have been synthesized and their optoelectrochemical properties examined. Polyphenylenes containing electronically isolated emitter centers have optical absorption and luminescence characteristics which are a function...

Poly(di-2-thienylphenylene) (2a), poly(di-2-thienyl-2,5-dimethylphenylene) (2b), and poly-(di-2-thienyl-2,5-dimethoxyphenylene (2c) have been prepared to examine the effect of substitution on polymer structure and ultimately their physical, optical, electrical, and electrochemical properties. The polymers contain no configurational isomerism due to...

A series of polymers containing alternating biheterocycle and p-phenylene repeat units has been synthesized and studied. When the heterocyclic unit is thiophene, the materials demonstrate electrochemical properties similar to those found for polythiophenes and retain the synthetic flexibility for substitution found in phenylene compounds. The monom...

In situ electron paramagnetic resonance (EPR)/electrochemistry methods have been used to elucidate the potential dependence of the presence of polaron and bipolaron charge carriers in poly(di-2-thienyl-2,5-diheptoxyphenylene).

A series of aromatic polymers and copolymers have been investigated that contain a combination of 2,5-thienylene and 1,4-phenylene linkages. l,4-Bis-(2-thienyl)phenylene monomers have been prepared with a variety of substituents on the 2,5-phenylene positions. Subsequent oxidative polymerization of these monomers, both chemically and electrochemica...

A superconducting magnetic energy storage apparatus comprising a cylindrical superconducting coil; a cylindrical coil containment vessel enclosing the coil and adapted to hold a liquid, such as liquefied helium; and a cylindrical vacuum vessel enclosing the coil containment vessel and located in a restraining structure having inner and outer circum...

DOI:https://doi.org/10.1103/PhysRevSeriesI.19.117