CREATION OF WEARPROOF SURFACES OF FRICTION PAIRS WORKING IN THE CONDITIONS OF LIQUID AND BORDER GREASING

Abstract

The paper describes the developed technology of the creation of wear-resistant surfaces of friction pairs, which have oil pockets for the holding of lubricants, which are situated between rollers, formed on flat surfaces with the help of a fast-rotating disk. The treatment of friction surface is performed by the disk of the thickness of 6 – 15 mm with reinforced working surface of solid VK-8 alloy. The disk rotates with the surface velocity of 50 – 150 m/c, it is pressed with the pressure of 1.2 – 40.0 MPa. It also shifts along the treated surface with the velocity of 3 – 30 mm/c. In the local treatment zone the metal of the processed surface, which has a ferrite-pearlite structure, is heated up to the temperature of 1100 – 1200 °С and transfers into an austenitic condition. Then the disk is moving beyond the treatment zone, the heated layer is chilled sharply by means of heat transfer into the mass of the detail. The structural transformation of austenite into martensite happens with the change of crystal lattice from the face-centered cubical lattice into a body-centered tetragonal one with the increase of the volume of heated metal. The increased volume, limited with the metal from three sides of the detail, is pressed above the treated surface up to the height of 0.3 – 1.5 mm and forms a buckled roller of martensite behind the moving disk. Here one can observe compressing stress and the degree of deformation up to 240 %. The rollers are formed along the whole surface from the edge to the edge in the direction, which is perpendicular to the motion of the workpiece during the operation process. Inclined (wedge-like) working surfaces of rollers provide the hydrodynamic supporting forces at sliding velocity of friction surfaces, which is more than 2 – 3 m/c (liquid lubrication), but supporting surfaces of rollers are made of a very hard material, allowing keeping wear-resistance in the conditions of boundary lubrication at slow sliding velocities of friction surfaces (less than 2 m/c).