Methods of data analysis for the ball cratering test on TiN and DLC coated steel

Abstract

Titanium nitride (TiN) coatings are widely used in machining because of its mechanical characteristics which modify the surface of the substrate increasing the capacity of load support and reduction of friction, while a coating as diamond-like carbon (DLC), which also has interesting mechanical properties, needs better attention. In this sense, the development of new coatings such as DLC is as important as wear analysis techniques. This work discusses the methods available to assess abrasive wear of coatings. For this, it has been used the data of the crater volume formed in ball cratering test and compared the difference between the specific wear coefficients of substrate and coating (ks and kc). These coefficients depend of the methods used for data analyses, thus, it has been used four equations to calculate ks and kc. Moreover, profilometry (pf) has been used to calculate the volumes, and thus ks and kc. Also, the roughness of the coatings, the thickness, the images corresponding to the crater formed, the coefficient of friction, the data obtained in wear tests due to the volume removed and, in the end, a comparison between ks and kc by different methods of data analyzes are presented.

Study on the Tribological Behavior of Wear and Friction Coefficient on AISI M35 High-Speed Steel with and without DLC Coating

“…A 71% reduction was obtained on the DLC-coated surface (k = 5.27E-14±6.55E-15 m 3 /N.m) in relation to the AISI M35 substrate (k = 1.83E-13±3.25E-14 m 3 /N.m). The graphical analysis reinforces the previous discussion about wear caps, showing that the coating application can provide improvements in tribological properties, in this case, resistance to abrasive wear 1,21,65 . also mentioned expressive differences in wear reduction when applying the DLC.…”

“…From pre-tests performed, it was observed the satisfactory formation of the wear caps under constant parametric conditions of normal load in the value of 0.403 N, rotation of the ball at 1000 rpm in a contact time of 5 minutes. These values are similar to those used by 21 (normal load) 37 , (rotation) and 36 (test time). The generated craters were analyzed and measured using SEM and, finally, the average wear coefficient k (m 3 /N.m) of each material studied was calculated according to Archard's Equation 1:…”

“…Both optical and scanning electron microscopy were used to measure the diameters of the wear caps produced on the surfaces. As in other studies, measurement uncertainties are often mentioned in the analysis of the results, as the craters produced do not always have a circumference shape, in top view, the edges are not well defined 21 . It is also worth mentioning that microscopy is a fundamental technique for the "wear impression" analysis generated on the surface, because the craters identification is due to the difference in tone of the SEM image as a function of the differences in electron penetration depth.…”

“…Therefore, it was not possible to say whether the increase in roughness after the deposition of the film (Figure 6b and Table 4) provided benefits or harms. As an example 21 , compared the resistance to micro-abrasive wear between titanium nitride (TiN) and DLC coatings deposited on AISI M2 steel. The roughness measured by AFM was 90 nm and 62 nm, respectively.…”

“…Several tribological tests are available according to the expected characterization objectives, which generally require low cost of experimental apparatus and the possibility of using small-scale samples 21 . The micro-abrasion wear test is one example, in which it is possible to measure the thickness and abrasive wear resistance of bulk materials as well as coatings 22 .…”