The Strengthen Of The Stainless Steel Thread Surface In The Vavle

Valve is widely used in the power system of the launch vehicle. It is a keypart to realize the function of the switching on and off, direction changing andadjustment. For the launch vehicle, the performance of the valve is directlyinfluenced by thread pairs. As the adjustment and execution part, the wearresistance is a crucial index. Austenitic stainless steel is commonly used in thevalve of the launch vehicle. But the hardness and wear resistance of austeniticstainless steel is not enough to meet the process require. Improving the wearresistance of thread pairs is consequently necessary.The process of plasma-based low-energy nitrogen ion implantation is usedin the surface modification of1Cr18Ni9Ti Austenitic stainless steel and2Cr13Martensitic stainless steel.An experiment under the ball-disc dry friction condition was done toresearch the wear resistance of2Cr13Martensitic stainless steel. The resultshows that the friction coefficient of2Cr13Martensitic stainless steel isdecreased. The depth and the width of scar is shallower and narrower, separately.The wear resistance is significantly improved.The comparing experiment is done to research the thread pairs made of thetwo kinds of stainless steels mentioned above. The data show that the10μmdepth from surface to the modification layer, the micro hardness of the valvethread pairs using modification1Cr18Ni9Ti Austenitic stainless steel and2Cr13Martensitic stainless steel is10-16GPa HV0.25Nand8-12GPa HV0.25N.Comparing to the original material, the hardness is increased5-8times and2.6-4times.Finally, the typical valve thread pairs are used in the dry friction test,fatigue life test and corrosion test. The results showed that the modificationlayer of the thread pairs is basically the same as standard sample results. Thewear resistance and stress relaxation properties have a very good performance.The corrosion resistance is better, which meet the carrier mission environmentand conditions.