STRENGTHENING OF INTERNAL SURFACES OF HOLES WITH RELATIVELY SMALL DIAMETERS

Abstract

Increasing the wear resistance of the internal surfaces of small holes, which include holes with a ratio of the internal diameter to the length (depth) of the hole exceeding the value of four for through holes and two for blind holes, is of important national economic importance. Almost all kinematic friction pairs with translational motion in machine building (internal surfaces of pneumatic and hydraulic cylinders, surfaces of material cylinders of thermoplastic automatic machines, surfaces of plunger pumps of fuel equipment of engines, barrels of mortars, guns, etc.) belong to this category of holes. One of the effective ways to increase the wear resistance of such holes is hydrogen-free glow discharge nitriding (BAT). However, glow discharge nitriding with constant current supply does not ensure uniform treatment of the internal surface over the entire depth, and with significant length-to-diameter ratios, the internal surface of the hole remote from the ends is practically not nitrided. Therefore, the technology of the hydrogen-free nitriding process in a glow discharge (GBN) with cyclically switched power supply (CSPS) has been developed.

The main regularities and conditions of nitriding in a glow discharge of relatively small diameter holes are established. The possibility of the main processes of nitriding of such holes under different types of gas discharge is analyzed. Recommendations are offered regarding the parameters of the energy discharge in the gas to ensure the efficiency of the process of modifying the internal surfaces of relatively small diameter holes. The main regularities that characterize the technological features of nitriding of the internal surface of holes are given.