TY - THES

T1 - Experimental wear evaluation of a diamond-like carbon coated pin and a steel roller using a modified component test

AU - Scharf, Raphael

N1 - embargoed until 13-09-2027

PY - 2022

Y1 - 2022

N2 - An increasing lifetime of different machine elements would save several gigatons of resources all over the world. Therefore, wear protection becomes more and more important. The time of functionality can be extended and it is not necessary to use new resources for replacing these parts. To improve the wear resistance, materials are coated with thin hard coatings, like diamond-like carbon (DLC). DLC is a hard coating, which consists of sp3 (diamond) and sp2 (graphite) bondings. Beside wear protection the reduction of friction is an omnipresent topic of research. To reduce the friction in engine components, oil additives, especially friction modifiers (FMs), are used. One common FM is molybdenum dithiocarbamate (MoDTC). Unfortunately, an increasing Mo content in an oil leads to a worse wear resistance of DLC, due to the formation of molybdenum carbides and oxides. Within this thesis, a test rig for the contact between a rotating steel roller and a stationary fixed pin, which is coated with DLC, was developed. The test rig was installed on the rotation module of a SRV5 tribometer. Load step tests and constant load tests were conducted. To lubricate the contact, an adjustable hose pump was used. Two different oils were used for the tests, one with a significantly higher level of Mo. Both oils have the same SAE grade, 10W-30. The performed test using an oil with a significantly higher level of Mo showed a clear visible wear pattern and a maximum wear depth of 1.3 µm. On the surface of the test with the low Mo containing oil, nearly no wear pattern was visible. Only a few minor scratches with a maximum depth of 1 µm could be detected. If these results are compared to the literature, similar results for ball on disc tests, that were already released, can be observed for the component tests, that were conducted for this master thesis under similar conditions (temperature, speed and lubrication) as in the engine. Depending on the test duration, the contact surface of the DLC pin was either polished or polished followed by delamination. This wear mechanism also was observed in the literature for pin on plate tests. Within this work it was possible to show that component tests, which are more comparable to the real application, are similar to already published model tests. Nevertheless, further tests are necessary to confirm these findings and the reproducibility of the tests.

AB - An increasing lifetime of different machine elements would save several gigatons of resources all over the world. Therefore, wear protection becomes more and more important. The time of functionality can be extended and it is not necessary to use new resources for replacing these parts. To improve the wear resistance, materials are coated with thin hard coatings, like diamond-like carbon (DLC). DLC is a hard coating, which consists of sp3 (diamond) and sp2 (graphite) bondings. Beside wear protection the reduction of friction is an omnipresent topic of research. To reduce the friction in engine components, oil additives, especially friction modifiers (FMs), are used. One common FM is molybdenum dithiocarbamate (MoDTC). Unfortunately, an increasing Mo content in an oil leads to a worse wear resistance of DLC, due to the formation of molybdenum carbides and oxides. Within this thesis, a test rig for the contact between a rotating steel roller and a stationary fixed pin, which is coated with DLC, was developed. The test rig was installed on the rotation module of a SRV5 tribometer. Load step tests and constant load tests were conducted. To lubricate the contact, an adjustable hose pump was used. Two different oils were used for the tests, one with a significantly higher level of Mo. Both oils have the same SAE grade, 10W-30. The performed test using an oil with a significantly higher level of Mo showed a clear visible wear pattern and a maximum wear depth of 1.3 µm. On the surface of the test with the low Mo containing oil, nearly no wear pattern was visible. Only a few minor scratches with a maximum depth of 1 µm could be detected. If these results are compared to the literature, similar results for ball on disc tests, that were already released, can be observed for the component tests, that were conducted for this master thesis under similar conditions (temperature, speed and lubrication) as in the engine. Depending on the test duration, the contact surface of the DLC pin was either polished or polished followed by delamination. This wear mechanism also was observed in the literature for pin on plate tests. Within this work it was possible to show that component tests, which are more comparable to the real application, are similar to already published model tests. Nevertheless, further tests are necessary to confirm these findings and the reproducibility of the tests.

KW - Diamonond-like carbon

KW - DLC

KW - MoDTC

KW - Stift-Rolle-Kontakt

KW - Diamonond-like carbon

KW - DLC

KW - MoDTC

KW - Pin-roller

M3 - Master's Thesis

ER -