Advanced Heat Resistant Materials Research Articles

High-power laser irradiation for high-temperature in situ transmission electron microscopy

We developed high temperature in situ transmission electron microscopy using a high-density laser irradiation device (nominal maximum laser density ~9.4 GW/m2) and a corresponding heat shielding sample mount device. The spatial line resolution of the microscope was maintained to be 0.14 nm at ambient temperatures after the installation of the laser irradiation device. The system was applied to the investigation of high temperature structural variation in tungsten plates. When the laser power was increased up to irradiation densities of approximately 61–280 MW/m2 (laser source output: 130–590 mW) to degrade tungsten plates, the microscope was undamaged. The surface dynamics was observed in situ by lattice imaging at irradiation densities of approximately 61–75 MW/m2 (laser source output: 130–160 mW); the spatial line resolution of the microscope was maintained to be 0.23 nm at high temperatures. It was expected that high temperature observation is realized using this heating system, which can be applied to the investigation of various advanced heat-resistant materials. We found using this heating system that degradation in tungsten plates started from surfaces and progressed through the preferential generation of characteristic defects, such as atomistic and nanometer holes and rods, and their subsequent evolution in thinner regions during the heating. It was demonstrated that the holes and rod were truncated with {110} sidewalls, i.e., these surfaces were stable in tungsten at high temperatures.

Deformation behaviour in advanced heat resistant materials during slow strain rate testing at elevated temperature

In this study, slow strain rate tensile testing at elevated temperature is used to evaluate the influence of temperature and strain rate on deformation behaviour in two different austenitic alloys. One austenitic stainless steel (AISI 316L) and one nickel-base alloy (Alloy 617) have been investigated. Scanning electron microscopy related techniques as electron channelling contrast imaging and electron backscattering diffraction have been used to study the damage and fracture micromechanisms. For both alloys the dominante damage micromechanisms are slip bands and planar slip interacting with grain bounderies or precipitates causing strain concentrations. The dominante fracture micromechanism when using a slow strain rate at elevated temperature, is microcracks at grain bounderies due to grain boundery embrittlement caused by precipitates. The decrease in strain rate seems to have a small influence on dynamic strain ageing at 650°C.

Final Report of the Key Technology Development Program for a Next-Generation High-Temperature Gas Turbine

There is a strong demand for efficient and clean power-generating systems to meet recent energy-saving requirements and environmental regulations. A combined cycle power plant is one of the best solutions to the above [1]. Tohoku Electric Power Co., Inc., and Mitsubishi Heavy Industries, Ltd., have jointly developed three key technologies for a next-generation 1500°C class gas turbine. The three key technologies consist of: (1) high-temperature low-NOx combustion system. (2) row 1 turbine vane and blade with advanced cooling schemes, and (3) advanced heat-resistant materials; (2) and (3) were verified by HTDU (High Temperature Demonstration Unit). This paper describes the results of the above-mentioned six-year joint development.

Key Technology Development for a Next Generation High Temperature Gas Turbine.

Touhoku Electric Power Company and Mitsubishi Heavy Industries, Ltd. are now jointly developing key technologies of a next generation high temperature gas turbine. The gas turbine operates at a 1500°C firing temperature and a thermal efficiency of a combined cycle plant which consists of the gas turbine and a steam turbine cycle is expected over 55% (LHV). The key of the gas turbine are dry low NOx combustion system technology, an innovative blade cooling and advanced heat resistant materials. The selected technologies for the purpose are a premixed dry low NOx combustion system, a full coverage film cooling and a directional solidified blade. The program consists of two phases. The first phase is the evaluation of the candidate technologies and the second phase is the improvement of the technologies for practical application. The paper describes an outline of the joint development program.