TY  - JOUR
AU  - Raumann, Leonard
AU  - Coenen, Jan Willem
AU  - Riesch, Johann
AU  - Mao, Yiran
AU  - Schwalenberg, Daniel
AU  - Gietl, Hanns
AU  - Linsmeier, Christian
AU  - Guillon, Olivier
TI  - Improving the W Coating Uniformity by a COMSOL Model-Based CVD Parameter Study for Denser Wf/W Composites
JO  - Metals
VL  - 11
IS  - 7
SN  - 2075-4701
CY  - Basel
PB  - MDPI
M1  - FZJ-2021-03231
SP  - 1089 -
PY  - 2021
AB  - Tungsten (W) has the unique combination of excellent thermal properties, low sputter yield, low hydrogen retention, and acceptable activation. Therefore, W is presently the main candidate for the first wall and armor material for future fusion devices. However, its intrinsic brittleness and its embrittlement during operation bears the risk of a sudden and catastrophic component failure. As a countermeasure, tungsten fiber-reinforced tungsten (Wf/W) composites exhibiting extrinsic toughening are being developed. A possible Wf/W production route is chemical vapor deposition (CVD) by reducing WF6 with H2 on heated W fabrics. The challenge here is that the growing CVD-W can seal gaseous domains leading to strength reducing pores. In previous work, CVD models for Wf/W synthesis were developed with COMSOL Multiphysics and validated experimentally. In the present article, these models were applied to conduct a parameter study to optimize the coating uniformity, the relative density, the WF6 demand, and the process time. A low temperature and a low total pressure increase the process time, but in return lead to very uniform W layers at the micro and macro scales and thus to an optimized relative density of the Wf/W composite. High H2 and low WF6 gas flow rates lead to a slightly shorter process time and an improved coating uniformity as long as WF6 is not depleted, which can be avoided by applying the presented reactor model.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000676817800001
DO  - DOI:10.3390/met11071089
UR  - https://juser.fz-juelich.de/record/894452
ER  -