Physical and Chemical Geotechnologies

Purpose

It has been investigated the influence of multi-layered vacuum-arc nanostructure coating Ti - Mo - N on wear resistance of piston rings. The influence of vacuum-arc coating parameters on nanohardness has been set.

Methodology

The material on the multi-layered coating was applied by means of vacuum-arc method was the grey cast-iron widely used in different branches of engineering. Multi-layered two-phase nanostructural coatings TiN - MoN were precipitated in the vacuum-arc plant "Булат-6". Nanoindentation was conducted by means of a pyramid of Berkovich at loading 0,5 H with loading and unloading executed automatically. Metallography researches were conducted by means of electronic microscope, study of the structural state of coverages was performed on a scanning microscope. The quantity of residual stresses in near-surface layers was determined on the plant ДРОН-2 by means of procedure of multiplied inclined shootings in radiation of copper anode with graphite monochromator. The tests for wear resistance were performed on the plant CMЦ-2.

Findings

Received dependences testify that nanohardness and given Young's modulus are of maximal in surface layers. The analysis of deflected mode has demonstrated that the highest value of compression (2.2 %) corresponds to the depth ~ 10nm. And maximal value of nanohardness takes place on the depth ~10 nm. The reason of residual stresses is an impact of ionic bombardment.

Research of the structural state of coatings showed that at the layer thickness about 2 nм there is no interface border and that’s why a spectrum is revealed on diffractive spectrums that is typical for monophasic state and material is hardened not much. The hardness increases at occurrence of the second phase. Thus, as follows from the results of studying the coatings by means of the scanning microscope, the cells on the coating surface are expressed in relief, that can be explained by means of the processes of their dispersion by the ions of molybdenum and titan during precipitation

In case of studying the layers of thickness  10 nm it is observed the forming of two-phase structural state. The interfaces occupy a large specific volume, that is accompanied by the increasing of compressive stresses. It must result in hardening, The research of layers of thickness  20 nm showed more washed out interface

Summary

Linear wear of cast-iron sprayed with coating Ti–Mo–N decreases in 8 times. Nanohardness increases on proximately 40 % in the same conditions of spraying at continuous rotation with the increasing of amount of layers from 1800 to 2700. Nanohardness increases on proximately on 25% at increasing of vacuum for all identical parameters of spraying the coating. The vacuum-arc precipitation performed at impulse voltage on a base Unu, equal to 2000 provides the increasing of nanohardness on 30 % as compare to without impulse one at all other equal conditions for conducting the experiment. They contain the researches? With were conducted within the project GP -516, 18/04/2016.

Keywords: vacuum-arc coating, nanohardness, wear resistance, piston rings

References

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