Analysis of the tribological behavior of diamond-like carbon coatings applied to AISI M2 high-speed steel

Abstract

Amorphous carbon coatings, known as Diamond-like Carbon (DLC), are thin coatings comprising amorphous carbon with sp² (graphite) and sp³ (diamond) bonds in varying proportions. These coatings are characterized by their high hardness and chemical inertness. Their application aims to effectively enhance the chemical, physical, and mechanical properties of conventional metals used as substrates, providing protection against abrasive and adhesive wear. The development of other DLC coatings is being studied for application under various conditions and on different non-ferrous metal alloys. This study proposes to evaluate and characterize DLC (Type A) and DLC with CrN interlayer (Type B) coatings using techniques such as Raman spectroscopy, X-ray Diffraction, Rockwell C adhesion test, and micro-abrasive wear test. Results showed that the total thickness of the Type B coating was approximately twice that of the Type A coating. Both showed a DLC layer of the a-C:H class. Comparing the crystallinity spectra, a higher level of amorphization was observed in the Type B DLC. In the adhesion test, classes HF2 and HF1, based on VDI 3198 standard, were assigned to the Type A and Type B coatings, respectively. Analyzing the cutting tools, changes in the surface texture on the rake face were observed, where the feed marks were completely covered when the Type B coating was applied. In the micro-abrasive wear test, it was found that the wear coefficients obtained with the coatings represented only 27 % of the value obtained on the high-speed steel substrate, which shows a difference of 63 % in the wear coefficient.