Research on Ceramic Coating Seal Valve Applied Technology
Sun Xinxin
CNKI
ABSTRACT
The spherical cone sealing structure is widely used in aerospace and chemical in- dustry,research and improvement on its sealing performance have certain applying worth in engineering. This structure in filling tube connector is the crucial component for injecting propellant. The connector presently used is typically made of 1Cr18Ni9Ti, and it has undergone pickling processes to increase the surface finish and the anti-oxidant capacity;however, it has not been subjected to special heat treatment. The majority of it used at present are designed for single use; as such, they are unable to meet the possibility of the propellant being damaged several times. If the filling tube connector does not comply with the strict tightening torque standards, its sealing performance will reduce after reuse. Further, as the connector is both made of stainless steel, when being used in space, the contact surface is prone to cold welding, which leads to sealing failure.
To solve the above problem, experiments were conducted to study the sealing performance of the filling tube connector, such as applying ceramic coating, heat treatment,and tightening torque management, and the best method is determined in the process. The stress distribution of contact surface is simulated by the FEM software ANSYS. Besides this,an electron microscope was used to observe the spherical surface of a leaky filling tube connector to get the failure mechanism.
Through the experimental study, we have found the best form of a filling tube connector, which is a model with titanium nitride coating connection and a plug that has undergone heat treatment. This form, applied with tightening torque management, has the best sealing performance. The results of finite element simulation indicates that the maximum stress decreases with the increasing thickness of coating, and the minimum occurs when the elastic modulus of the matrix is similar to that of the coating. The results of the electron microscope analysis shows that the failure of the original and heat treatment filling tube connector is mainly due to debris abrasion and adhesion abrasion, and that of connector with coating occurs primarily due to the brittle spalling and furrows on the coating.
Key words: Seal; coating; heat treatment; tightening torque management
|
