Improving the W Coating Uniformity by a COMSOL Model-Based CVD Parameter Study for Denser Wf/W Composites

Improving the W Coating Uniformity by a COMSOL Model-Based CVD Parameter Study for Denser Wf/W Composites

Blog Article

Tungsten (W) has the unique combination of excellent thermal properties, low sputter yield, low hydrogen retention, PLUS EPA 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 International 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.