The results of work are described to determine optimal materials for one of the elements of middle position lock to increase load bearing characteristics and contact resistance of the middle position lock. The results are presented of experimental check of impact of material of rod with hydraulic actuator piston on contact resistance and load capacity of the middle position lock of thrust vector control system two-channel hydraulic actuator. As replacer, the 18ХГТ steel was selected allowing (after carbonization and hardening) obtaining in surface layer of material the HRCэ 56-62 hardness with plastic core, instead of HRCэ 36-42 after hardening of applied 09Х16Н4Б steel. The comparative results were obtained in the tests of experimental sample of the lock completed with two rods with piston: the rod with piston manufactured according to DD and the experimental rod with piston that passed carbonization to the depth 0.9-1.3 mm and hardened to HRCэ 56-62. The rod’s ring groove - one of the elements of lock was subjected to carbonization and hardening. Both rods with piston were tested in the lock’s dummy in the load range: up to 1200 kgf –standard rod with piston and up to 3000 kgf – experimental rod with piston under static and cyclic loading. The test results are positive: the standard rod with piston confirmed its serviceability at the loads up to 1200 kgf inclusive; the experimental rod with piston withstood the loads up to 3000 kgf under static and cyclic loading. The evaluation of contact resistance was made by comparison of dimensions of traces left by the balls on the surface of rod’s grove under lock loading. The dimensions of traces on the experimental rod with piston under the load 3000 kgf inclusive did not exceed the dimensions of traces on the standard rod with piston, which testifies to the increase of contact resistance. We believe that the direction of search for steel brands in combination with advanced methods of thermal treatment is promising in increasing the lock’s load-bearing characteristics.
Key words: thrust vector control system, main engine, tests, rod with piston.