CS261694B1 - A method of treating surface and subsurface layers of rolling contact surfaces - Google Patents

Abstract

The essence of the method of treating rolling contact surfaces is that the active parts of bearing steel or steel grade 12, 17 and 19 annealed, optionally treated with an antireflox layer, are polished to roughness Ra = 0.4 to 0 after laser beam turbidity. , 2 μΐη, whereby the hard abrasion resistant layers of TiN, TiC, Ti (CN) are formed, eventually by the method of reactive ion plating.

Description

BACKGROUND OF THE INVENTION The present invention relates to a method of treating surface and subsurface layers in contact surfaces of a rolling by laser beam heat treatment and a reactive ion plating method.

For some cases in the rolling process it is necessary to provide bearings with a long lifetime (eg bearings in drilling rigs). From this point of view, the subsurface area and surface where damage occurs most often appear to be important to increase contact fatigue resistance.

Simplified Hertz relations are used to calculate the main characteristics of the contact beams during rolling, based on which the maximum normal stress (6 max), the maximum unidirectional shear stress (τ max) and the maximum change in alternating shear stress (Δτ max) can be determined. shear stress is located at a certain depth below the surface.

Most experts agree that shear stresses are dangerous for fractures or cracks, and that the zone below the surface in which the fatigue micro-cracks are formed is from 0.003 to> 0.145 mm depending on the size of the load. Pitting is caused by breaking the surface to the points of subsurface cracks that are closest to the surface.

In addition, the following forms of damage occur most frequently on the surface itself:

(a) wear

b) seizure (material deposition)

(c) permanent impressions

(e) overheating

(f) peeled

More methods and technologies of rolling contact surface treatment are now known. The best known are surface hardening, cementation and induction hardening. The disadvantage of these methods is:

- Uneven heating · - Collapse and ovality - Hardly reproducible results in operation - High local stress concentration with acute risk of cracking - High sensitivity to changes in external conditions (heating, cooling).

The aforementioned drawbacks are solved by the method of treatment of the rolling contact surfaces according to the invention, which is based on the fact that the rolling surface of the bearing steel materials of steels of classes 12, 17 and 19 opaque coated with antireflective coating is irradiated with a laser beam ° to 95 °, at an area power density in the range of 10 ³ to 10 ^B Wcm a ² and an energy density in the range of 10 10 ⁶ to 150.10 ^e MJm ^-2 , with a trace of overlap between 0.1 and 0.4 mm; and the surface thus treated is then polished to a surface roughness Ra of 0.4 to 0.2 µm, after which the surface thus prepared is treated with a plasma formed by vapors of titanium and reactive gas (most often nitrogen, ethene or ethine, or a mixture thereof) ), eventually by vapors W, at the destroyed pressure from the interval 10 ^-3 to 10 ^ a.

This method can be advantageously applied to the raceways of roller bearings, which are used in extremely stressed bearings and in bearings whose dismantling is time-consuming and labor intensive. Although the method is expensive to invest, the resultant effect is balanced by the long life of the bearing.

The invention is illustrated by the example below.

Example:

On contact surfaces of rolling in the initial state - bearing steel, respectively. tr. 12, 17 and 19, annealed or softened, an anti-reflective layer is applied. The contact surfaces become turbid by moving the sample, respectively. by moving the laser beam of the continuous CO2 laser with the following laser parameters: laser power 1 kW, focusing mirror, beam moving across the contact flat to the width of the surface over the entire contact time, at 90 ° + 5 ° beam incident angle, , 2 mm, at a speed of 1 µL / min. The surface is completed by polishing - superfinishing.

Hard and abrasion resistant layers, such as TiN, are formed on the surface prepared in this way, the technological preparation of which is as follows:

After cleaning the component, which is at a negative potential of up to 5 kV in glaring argon at a pressure of 2 Pa for at least 30 minutes, the titanium is evaporated to the vacuum chamber by means of an electron beam source at a power of 2 kW. At the same time, nitrogen is introduced into the vacuum chamber at a pressure of 0.1 Pa, which is split in the chamber to form a TiN layer whose thickness should not be greater than 3.0 μτα.

The present invention can be used mainly in the field of rolling bearings in extremely stressed bearings. In other fields, parts with very high stresses on the contact surfaces occur in rolling processes.

Claims (1)

SUBJECT Method of treatment of surface and subsurface layers of contact surfaces of rolling parts of bearing steel materials, steels of classes 12, 17, 19 annealed or refined by laser irradiation and subsequent ion-cladding characterized in that the surface with antireflective coating is irradiated by a laser beam at an incidence angle in the range of 85 ° to 95 °, at an area power density in the range of 10 ³ to 10 ⁶ Wcnr ^2, and OF THE INVENTION energy density in the range 10.10 ⁶ to 150.. 10 ^B MJm ² , where the trace of the beam overlaps in the range 0.1 to 0.4 mm and the surface treated in this way is then polished to a surface roughness Ra = 0.4 to 0.2 μΐη, after which the surface prepared in this way is applied plasma consisting of vapors of titanium and reactive gas, most often nitrogen, ethene or ethine, or a mixture thereof, or vapors W, under reduced pressure, in the range 10 ³ to 10 ¹ Pa.