RU2373520C1 - Method of evaluation of relative wear resistance of materials - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention refers to testing of materials for wear and can be implemented at assessment of wear resistance of materials of hardened layers of considerable thickness and/or high resistance to wear under influence of abrasive materials on them. A sample is made out of reference material by means of running-in of both end surfaces of material and by forming a hardened layer on one of surfaces. A prepared sample is worn out by rubbing-in along abrasive surface not exceeding thickness of hardened layer. After running-in and wear change of linear dimensions of the sample is evaluated. Further the sample is turned at 180° and reference material is worn out. Residual linear dimension of the sample is assessed and relative wear resistance is calculated.

EFFECT: enhanced efficiency of assessment of material wear resistance and upgraded accuracy of results.

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Description

The invention relates to tests of materials for wear and can be used to assess the wear resistance of materials of hardened layers (coatings) of significant thickness and / or characterized by high resistance to wear when abrasive materials act on them.

A large number of schemes, devices and methods are known that allow testing materials under abrasive conditions. An analogue of the proposed method is a test method for abrasive wear, proposed Khrushchov MM (for a more detailed description, see MM Khrushchov Patterns of abrasive wear. Sat. Wear resistance, publishing house "Science", 1975, pp. 5-28). The method consists in the fact that the test and reference samples are rubbed against a surface with abrasive particles attached to it (abrasive skin) under static load and in the absence of heating, worn samples are measured or weighed, and the results are compared.

The closest technical solution is the method (RF Patent No. 2315284. IPC G01N 19/02. Bull. No. 2 dated January 20, 2008), which consists in the formation of two identical samples from the reference material by applying a strengthened layer (coating ), running in the surface of the hardened layer (coating), wearing one of the formed samples by abrasion on the abrasive surface to a depth exceeding the thickness of the hardened layer, and evaluating its thickness using the second sample. The wear of the standard is carried out after wear of the hardened layer, linear dimensions are measured after running-in and after wear, and the wear resistance of the material of the hardened layer (coating) is judged by their ratio, calculating ε by the formula:

,

,

where S ₁ , S _MO - the friction path attributable to the wear of the hardened layer (coating) in excess of its thickness and the base material of the sample, respectively, m;

L ₀ , L ₁ , L _K , h _up - the dimensions of the sample: the original, after wear with excess coating or hardened layer (h _up ) and the final, after wear of the base material, respectively, mm.

However, this method has low productivity when testing materials of hardened layers (coatings) having high wear resistance and / or significant thickness (> 15 μm). Since in case of not exceeding the coating thickness in one test cycle, it is necessary to replace the abrasive material and continue to abrade the coating material until it is guaranteed to exceed its thickness. In this case, additional errors of the obtained results also arise due to the calculation of the friction path of the coating material as the total during wear over several test cycles.

The objective of the invention is to increase the productivity of determining the wear resistance of the material and increase the accuracy of the results obtained by their implementation.

The task of increasing productivity is solved due to the fact that the use of the proposed method for determining the relative wear resistance of the material becomes possible for testing hardened layers (coatings) of high wear resistance or significant thickness in situations where the hardened layer is not worn on a given friction path due to the rotation of the test sample 180 ° and the completion of the test of the reference material when using a previously prepared free of hardening of the end face of the sample. The task of increasing the accuracy of the obtained results is solved by eliminating the operation of determining the thickness of the hardened layer and the need to find the friction path as the sum of the paths on each of the additional test cycles required to exceed the coating thickness.

The method is implemented as follows:

- make a prototype of a reference material, in relation to which it is required to determine the relative wear resistance of the hardened layer (coating);

- break in both end surfaces of the test sample;

- form a hardened layer (coating) on one of the end surfaces of the sample;

- the working surface of the sample is subjected to running-in to achieve its tight fit to the wearing abrasive surface under conditions identical to the test conditions;

- measure the initial size of the test sample;

- a sample with a holder is mounted on a friction machine and the test hardened layer (coating) is abraded on an abrasive surface;

- fix the friction path of the previous test stage;

- measure the size of the worn sample;

- turn the sample 180 ° and wear out the base material;

- determine the final size of the sample;

- fix the path of friction attributable to wear of the base material;

- calculate the relative wear resistance according to the formula:

where S _n , S _MO is the friction path attributable to the wear of the hardened layer (coating) and the base material of the sample, respectively; L ₀ , L ₁ , L _K - sample dimensions: initial, after wear of the hardened layer and final, after wear of the reference material, respectively. The indicated designations are illustrated in the drawing.

Dependence (1) is obtained from the following reasoning. To calculate the relative wear resistance, it is necessary to correlate the volumes of worn base material and (conventionally reference) and the material of the hardened layer (coating) on equal friction paths, i.e. wear rates.

Denote the dimensional wear of the material of the hardened layer through J _n , the dimensional wear of the base material through J _MO . For them you can write:

We express the wear rate of the sample, correlating it with the corresponding wear rate of the hardened layer (coating), and define ε _yn as the quotient of their division:

where S _n , S _MO is the friction path attributable to the wear of part of the hardened layer (coating) and the base material of the sample, respectively.

After transformations and simplifications, taking into account (2), dependence (3) will take the form (1).

An example of a specific implementation of the method

The material of the reference sample is steel 45. The surface roughness is not higher than 1.2 microns in Ra. The end face of the test sample was subjected to sulfocyanination treatment at a temperature of 570 ° C for 1 hour. The hardened layer was run-in, the completion of the run-in was evaluated visually on an MBS-I optical microscope (× 50) by the equal surface gloss when traces of pretreatment disappeared. After sulfocyanination and repeated running-in of the modified surface, the initial size of the sample was measured L ₀ = 17.010 mm.

The sample was tested on a friction machine SRV-III according to the disk scheme (with abrasive skin) - finger. The rotation speed of the disk is 60 rpm, the radial feed per revolution is 1 mm. The static load is 3 N. After abrasion of part of the coating on the friction path S _n = 1 m, the linear dimension L ₁ = 16,995 mm was measured. All measurements of the linear dimensions of the samples were carried out with an accuracy of 1 μm using a vertical length gauge. Then the test was continued on the control part of the test sample after turning the latter through 180 ° in the holder, followed by the measurement of L _K = 16.879 after passing the friction path S _MO = 1 m

Substitute the found values in (1) and determine ε _{unitary enterprise} :

.

.

The wear resistance of the hardened layer formed during sulfocyanination treatment exceeds the wear resistance of steel 45 by 7.7 times.

Claims (1)

The method for determining the relative wear resistance of the material of the hardened layer, which consists in the fact that a hardened layer is formed on the working surface of the sample from the reference material, the surface is worked out and worn out by abrasion on the abrasive surface, the linear dimensions of the sample are measured before and after the tests, characterized in that they use one a sample with two run-in end surfaces, test for wear of the material of the hardened layer by an amount less than its thickness, and after turning 180 ° wear the reference material and the wear resistance of the hardened layer is judged by the ratio of changes in the linear dimensions of the sample after running-in and after wear according to the formula

where S _n , S _mo - the friction path attributable to the wear of the hardened layer and the base material of the sample, respectively; L ₀ , L ₁ , L _K - sample dimensions:
initial, after wear of the hardened layer and final after wear of the reference material, respectively.