A high power laser facility to conduct annealing tests at high temperature

Abstract

The knowledge of materials properties and their behavior at high temperatures is of crucial importance in many fields. For instance annealing phenomena occuring during the thermomechanical processing of materials, such as recrystallization, have long been recognized as being both of scientific interest and technological importance. Different methods are currently used to study annealing phenomena and submit metals to heat loads. In this work, we present the design and the development of a laser-based facility for annealing tests. This experimental setup enables studies at the laboratory scale with great flexibility to submit samples to various spatial and temporal heating profiles. Due to the possibility to have optical access to the sample, laser heating can be combined to several non-contact diagnostics such as infrared imaging to control and analyse the temperature gradients. As case study, we present a set of experiments performed to study the recrystallization kinetics of tungsten. We demonstrate that samples can be heated linearly with heating rate up to ∼2000 K/s, at temperatures above 2000K, for seconds or hours, with typical errors in the temperature measurement of around 1% that depend mainly on the determination of sample emissivity. Such studies are of crucial interest in the framework of nuclear fusion, since the ITER nuclear reactor will operate with a full-W divertor.

Recrystallization at high temperature of two tungsten materials complying with the ITER specifications

“…To heat the samples at high temperatures with minimal thermal transient, a laser heating approach is used. The experiment is based on the ChauCoLase facility (Chauffage Contrôlé par laser, lasercontrolled heating in english) which is described in details in [13]. In the present work, samples are annealed at temperature called Ta for duration called ta.…”

“…1). The temperature distribution in the sample has been estimated with Finite Elements Methods simulations [13]. During steady state loading, the temperature gradient across the material at Ta=1727 °C is below 20 °C and 30°C for batch A and batch B, respectively.…”

“…During steady state loading, the temperature gradient across the material at Ta=1727 °C is below 20 °C and 30°C for batch A and batch B, respectively. At Ta=1427°C it is below 10 °C and 11°C for batch A and batch B respectively Temperature deviations in the sample during the heating and cooling sequence were estimated to be below 2% compared to set Ta [13]. The experimental chamber is configured as shown in Fig.…”

“…This is the case for conventional facilities, for which heating speed is 5 °C/min. For these reasons, a new test bed was developed using a laser heating system [13]. The sample could be heated with a speed of 200 °C/s in low vacuum environment (10 -2 mbar).…”

An Attempt to Assess Recovery/Recrystallization Kinetics in Tungsten at High Temperature Using Statistical Nanoindentation Analysis

“…The recrystallization temperature of pure tungsten for 3600 s annealing has been reported to be in the range 1100-1500 • C [2,4,5]. It is necessary to measure the recrystallization kinetics in a temperature range closer to thermonuclear fusion applications though, which can only be done using a specific annealing set-up [6,7]. Nevertheless, this type of device can only process one sample at a time.…”