Prediction of long-term creep rupture data for 18Cr–12Ni–Mo steel

The existing length of the materials development cycle is currently far too long. Validation of a new methodology to reduce this time requires evidence of its applicability to a wide range of materials. This study focuses on 18Cr–12Ni–Mo steel because of its importance to future power generation. The methodology is shown to accurately predict the strengths of numerous batches of this material obtained from different … Continue reading Prediction of long-term creep rupture data for 18Cr–12Ni–Mo steel

Obtaining confidence limits for safe creep life in the presence of multi batch hierarchical databases: An application to 18Cr-12Ni-Mo steel

The creep and creep rupture properties of 18Cr–12Ni–Mo steel tubes have been analysed using the Wilshire equations. The observed behaviour patterns are then briefly discussed in terms of the dislocation processes governing creep strain accumulation. A suitable statistical framework for analysing both the single and multi batch data available on this material is then specified. It is shown that ignoring the hierarchical nature present in … Continue reading Obtaining confidence limits for safe creep life in the presence of multi batch hierarchical databases: An application to 18Cr-12Ni-Mo steel

A frailty model for the analysis and prediction of creep and creep fracture: with application to high temperature plant life assessment using 1Cr–1Mo–0.25V

This paper develops a modification of the shared frailty model that allows for the distribution of the response and the random effects to be determined by the data (from within the exponential family of distributions). A simulated maximum likelihood and a computationally simpler simulated linear least squares approach to estimating this model are also presented. These generalizations are important for modelling high-temperature deformation because they … Continue reading A frailty model for the analysis and prediction of creep and creep fracture: with application to high temperature plant life assessment using 1Cr–1Mo–0.25V

A multi-level model for the analysis and prediction of creep and creep fracture of 2.25Cr–1Mo steel tubes

The creep and creep rupture properties of 2.25Cr–1Mo steel tubes have been analysed using the Wilshire equations. The observed behaviour patterns are then discussed in terms of the dislocation processes governing creep strain accumulation. A suitable statistical framework for analysing both the single and multi batch data available on this material is then specified. It is shown that ignoring the hierarchical nature present in many … Continue reading A multi-level model for the analysis and prediction of creep and creep fracture of 2.25Cr–1Mo steel tubes

A Novel Approach to the Prediction of Long-Term Creep Fracture, with Application to 18Cr-12Ni-Mo Steel (Bar, Plate, and Tube)

Designers of new power-generation plants are looking to make use of new and existing high-strength austenitic steels so that these plants can operate with much higher steam and, therefore, metal temperatures. However, this article shows that the Wilshire–Scharning methodology is incapable of producing accurate long-term-life predictions of these materials from short-term data. This article puts forward a modification of this approach that should enable existing … Continue reading A Novel Approach to the Prediction of Long-Term Creep Fracture, with Application to 18Cr-12Ni-Mo Steel (Bar, Plate, and Tube)

A generalisation of the Wilshire–Scharning methodology to creep life prediction with application to 1Cr–1Mo–0.25 V rotor steel

Wilshire–Scharning have recently developed a new methodology that has been demonstrated to deliver accurate longer term creep life predictions, and so offers the prospect of cost-effective acquisition of long-term creep design data. This methodology differs from existing approaches to creep life prediction by normalising the applied stress through the appropriate tensile strength. This article develops a generalisation of this Wilshire–Scharning model that has the potential … Continue reading A generalisation of the Wilshire–Scharning methodology to creep life prediction with application to 1Cr–1Mo–0.25 V rotor steel

Alpha-Case Kinetics and Surface Crack Growth in the High-Temperature Alloy TIMETAL 834 Under Creep Conditions

Investigations of Timetal 834 crept specimens showed that a uniform alpha-case layer was developed at the surfaces of all specimens tested in air at 823 K to 923 K (550 °C to 650 °C). The formation of this alpha-case was a result of the inward diffusion of oxygen, which is an alpha stabilizer, and other elements promoting the transformation of the beta matrix into an alpha phase and, thus, … Continue reading Alpha-Case Kinetics and Surface Crack Growth in the High-Temperature Alloy TIMETAL 834 Under Creep Conditions