Abstract:

Objective In order to improve the friction and wear properties, prolong the service life of the steel collar and increase the efficiency of the steel collar in ring spinning machines, the friction and wear mechanism of diamond-like coating (DLC) on spinning steel collar at high temperature was studied, and the friction and wear resistance caused by the structure change of diamond-like coating was analyzed. In the actual running state, the force of diamond-like coating applied on the steel collar was analyzed, and the performance of diamond-like coating was studied through the maximum force value and the maximum deformation.

Method Cr-doped DLC coating was prepared by low temperature physical vapor deposition (PVD) coating technology on the surface of 20# steel. The surface morphology of DLC coating was studied using scanning electron microscope. The structure composition of DLC coating was analyzed by X-ray diffraction, energy spectrum and Raman spectrometer. Nanoindentation tester was a dopted to test the mechanical properties of the coating. High temperature friction and wear testing machine was a dopted to test the friction performance of the coating at different temperatures (25, 100, 200, 300 ℃), and the influence of the force on the friction process of the steel collar was analyzed by simulation.

Results From the friction test at different temperatures, the average friction factor of 20# and 20#-DLC samples were found to firstly increase and then decrease as temperature increased. At 300 ℃, 20# generated oxides, with a large amount of oxides formed an adhesion layer. The average friction coefficient was reduced to 0.54. The graphitization of 20#-DLC samples occurred at 200 ℃ and 300 ℃, forming a transfer layer dominated by carbon elements, and the transfer film replaced the attachment layer. The friction changed from coating to attachment layer to coating to transfer layer, and the average friction coefficient at the two interfaces was decreased to 0.145 and 0.107, respectively. DLC coating not only showed excellent anti-friction effect, but also reduced the stress and deformation in the process of friction. Through simulation analysis, the maximum stress value and maximum deformation of the steel collar after deposition of DLC coating were 4.20×10⁸ MPa and 1.47×10^-2 mm, respectively in actual operation.

Conclusion The DLC coating doped with Cr element was prepared on the substrate by low temperature PVD coating technology. The elastic modulus and hardness were 205.8 and 23.66 GPa, respectively. The coating surface showed honeycomb structure and amorphous structure. The average friction factors of 20# steel sample at 25, 100, 200 and 300 ℃ are 0.05, 0.62, 0.64 and 0.54, respectively. The average friction factors of 20#-DLC samples at 25, 100, 200 and 300 ℃ are 0.053, 0.213, 0.145 and 0.107, respectively. Under the same temperature conditions, the friction factor curve of 20#-DLC sample is significantly lower than that of 20# sample, and the DLC coating forms a transfer layer dominated by carbon elements at 200 ℃ and 300 ℃, which reduces the friction factor. DLC coating has excellent anti-friction properties and is suitable for textile steel collar working at high temperature. In the process of friction and wear, the two types of steel collar (20# and DLC-20#) showed different degrees of stress concentration and deformation at the lower right corner of the runway under the action of external forces. The maximum stress value and deformation amount of 20#-DLC are 4.20×10⁸ Pa and 9.69×10^-3 mm, respectively. The deformation of DLC coating absorbs part of the energy brought by the stress, which reduces the maximum stress value and deformation amount of the steel collar matrix.

Key words: steel collar, diamond-like coating, impact performance, transfer layer, friction property