Microstructure and Mechanical Properties of an Advanced Nickel-Based Superalloy in the as-HIP Form

This study evaluates the suitability of as-hot isostatically pressed (HIP) RR1000 for non-critical applications in aero-engine components. RR1000, an advanced powder nickel-based superalloy, was developed for disc rotor components in aero-engines. For these critical applications, the consolidated alloy powder particles are extruded to break down carbide and oxide networks, known as prior particle boundaries (PPBs), and to refine the structure into a fine grain size … Continue reading Microstructure and Mechanical Properties of an Advanced Nickel-Based Superalloy in the as-HIP Form

Crack growth in the creep-fatigue regime under constrained loading of thin sheet combustor alloys

Damage tolerant lifing methodologies are an essential requirement to support the safe and reliable operation of combustors in the modern gas turbine aero-engine. These static components experience a wide range of temperature superimposed upon a complex stress field resulting from their geometrical form. Features such as seam welds, injector ports and cooling hole arrays could potentially initiate and subsequently interact with fatigue cracks, while the … Continue reading Crack growth in the creep-fatigue regime under constrained loading of thin sheet combustor alloys

Surface topography and the impact on fatigue performance

Areal characterization was applied to plain fatigue specimens manufactured from a nickel-based superalloy, Alloy 720Li, to determine the impact of machined/finished surface topography on fatigue performance of this material. Samples were subjected to fatigue testing in the as-turned and shot peened conditions to study the interaction between residual stresses and topography in influencing the fatigue performance. The turning process was deliberately manipulated to produce three … Continue reading Surface topography and the impact on fatigue performance

Surface Roughness, Areal Topographic Measurement, and Correlation to LCF Behavior in a Nickel-Based Superalloy

Surface roughness often determines fatigue performance of advanced engineering components making definition of this parameter essential subsequent to manufacture. Traditionally, topography measurements employ an average amplitude parameter, Ra, obtained from a two-dimensional contact measurement. This parameter, however, is highly localised making it relatively unreliable. This study attempts to correlate areal (3D) topographic, measurements with the low cycle fatigue (LCF) performance defined for a nickel-based superalloy … Continue reading Surface Roughness, Areal Topographic Measurement, and Correlation to LCF Behavior in a Nickel-Based Superalloy

The effects of machined topography on fatigue life of a nickel based superalloy

The surface topography of engineering components is known to affect fatigue behaviour. However, defining topography based on the average roughness (Ra) parameter is considered to be inadequate when correlating to fatigue performance. Alternative correlations utilising areal topographic parameters would therefore be valuable. This has been addressed through areal topographic measurements and fatigue testing of an advanced nickel based superalloy, Alloy720Li. Low cycle and high cycle … Continue reading The effects of machined topography on fatigue life of a nickel based superalloy

A quantitative approach to study the effect of local texture and heterogeneous plastic strain on the deformation micromechanism in RR1000 nickel-based superalloy

In a weakly textured material with relatively pore-free and homogeneous microstructure, the local texture can influence primary crack propagation and secondary crack initiation, depending on specific microtexture cluster size. Moreover, the plastic strain assessment and strain quantity within individual grains are essential for understanding the material susceptibility to crack initiation and propagation at various loading conditions and temperature ranges. In the current study, electron backscatter … Continue reading A quantitative approach to study the effect of local texture and heterogeneous plastic strain on the deformation micromechanism in RR1000 nickel-based superalloy

Elevated Temperature Creep Deformation of a Single Crystal Superalloy through the Small Punch Creep Method

Small punch testing is now a widely recognised approach for obtaining useful mechanical property information of critical structural components, particularly in the nuclear industry. However, to date the utilisation of this method has been limited to isotropic materials such as aluminium alloys and steels.This paper will look to utilise the small punch(SP) test to assess the creep response of 〈001〉-orientated CMSX-4 at temperatures above 950°C. An orthogonal rafting … Continue reading Elevated Temperature Creep Deformation of a Single Crystal Superalloy through the Small Punch Creep Method

Creep Lifing Methodologies applied to a single crystal superalloy by use of small scale test techniques

In recent years,advances in creep data interpretation have been achieved either by modified Monkman–Grant relationships or through the more contemporary Wilshire equations, which offer the opportunity of predicting long term behaviour extrapolated from short term results. Long term lifing techniquesprove extremely useful in creep dominated applications, such as in the power generation industry and in particular nuclear where large static loads are applied, equally a reduction in … Continue reading Creep Lifing Methodologies applied to a single crystal superalloy by use of small scale test techniques

Crack Growth of a Polycrystalline Nickel Alloy under TMF Loading

Thermo-mechanical fatigue (TMF) is an important factor for consideration when designing aero engine components due to recent gas turbine development, thus understanding failure mechanisms through crack growth testing is imperative. In the current work, a TMF crack growth testing method has been developed utilising induction heating and direct current potential drop techniques for polycrystalline nickel-based superalloys, such as RR1000. Results have shown that in-phase (IP) testing produces accelerated crack growth … Continue reading Crack Growth of a Polycrystalline Nickel Alloy under TMF Loading

Development of true-stress creep model through analysis of constant-load creep data with application to finite element methods

The creep behaviour of the nickel-superalloy RR1000 is studied through a number of constant-load creep tests. It is often assumed that creep data generated by constant-load testing are unsuitable for building a generalised creep model due to the non-constant stresses incurred. Analysis of existing models shows that significant errors may occur in many approaches, which attempt to recreate the strain evolution with time. A model … Continue reading Development of true-stress creep model through analysis of constant-load creep data with application to finite element methods