Manufacturing Of CFETR Blanket First Wall W/Steel Mockup Using Hot Isostatic Pressing

The Water-Cooled blanket of CFETR(Chinese Fusion Engineering Test Reactor)consists of plasma facing material(W armor)and structural material(Ferristic/Martenstic steel).The severe environment in fusion reactor requires defect-free joint by metallurgical bonding.In order to solve this technical issue,manufacturing process of high-performance W and steel bonding joint by Hot Isostatic Pressing(HIP)was studied using simulation and experimental methods in this paper.Firstly,the distribution of residual stress in joint was calculated by ANSYS finite element method on W/steel joint containing different interlayers manufactured by HIP.The result shows that residual stress is affected by yield strength and thermal expansion coefficient(CTE)of interlayer materials.When residual stress is large enough,the metal with smaller yield strength tends to deform firstly.Interlayer with smaller yield stress can reduce the residual stress of W/steel joint effectively.Secondly,ANSYS finite element method was used to analyze the temperature field distribution of first wall small module containing an interlayer under thermal irradiation condition.With the thickness increase of interlayers,the maximum temperature of W and interlayer metal grow slowly and linearly,while temperature change of steel is smaller.When the thickness of Ti,Ni and Cu interlayer is less than 2 mm,temperatures of first wall are within the available temperature range of materials under thermal irradiation condition.On the basis of theoretical analysis,microstructure and property of W/interlayer/steel HIP joint with different interlayers were studied.The result shows that welded joint with higher mechanical strength can be obtained at higher temperature in the specific temperature range.Most of W/interlayer/steel welded joints are broken in brittle manner.Joints without brittle reaction products have higher bonding strength,and even fail in plastic form.High deuterium pressure(0.1 MPa)can lead to hydrogen embrittlement of the Ti interlayer of W/Ti/steel joint.In the future,it is necessary to study whether W/interlayer/steel joints are suitable for the hydrogen isotope environment in fusion reactor by using hydrogen isotope exposure method to prevent hydrogen inducing craking in metals.At last,microstructure and property of the steel during HIP process were studied.The optimum heat treatment process can restore property of steel The process is applied to heat treatment of W/interlayer/steel.Results show that after removing the canister,W/interlayer/steel joints are easy to crack in normalizing process,micro structure of steel in uncracked joints can restore to close to base metal level,but mechanical strength of W/interlayer/steel joint will be affected.By comparing the data from simulation and experiments,the following conclusion can be obtained:Cu and Ni bilayer metals will be preferred as the interlayer materials to weld W/steel in terms of interface reaction product,thermal stress release or final failure manner,if Cu and Ni are allowed to be used for future fusion reactor material.