New Abrasive Coatings: Abraded Volume Measurements in Ceramic Ball Production

Abstract

Technological progress in hybrid bearings developed high wear and abrasion resistant materials for rolling elements. The manufacturing process of bearing balls presents new challenges, as nowadays, it requires time-consuming and costly processes. In this frame, the bearing manufacturing industry is demanding improvements in materials, geometry, and processes. This work aims to investigate new abrasive coatings for grinding wheels for Si3N4 ball manufacturing. Tribological pin on disk tests are performed on samples of grinding materials (disk) versus a Si3N4 ball (pin). Two samples of specimens coated with an electrodeposited diamond and diamond-reinforced metal matrix composite are examined to measure the abrasion rate and the wear resistance of Silicon Nitride Si3N4 balls, considering the influence of sliding speed and the effect of coating deposition on diamond particle density and granulometry. The measurements estimated the specific wear coefficient k, the height wear surface h, and the wear rate u of the Si3N4 balls. The results pointed out that by increasing the sliding speed, the abraded volume increases for both the coatings. The parameters affecting the abrasion effectiveness of both the coatings are the surface roughness, the abrasive particle dimension, and the sliding speed.

Abrasion Power of Ti and Ni Diamond-Coated Coatings Deposited by Cold Spray

“…In [26], the test preload was lower (1 N vs. 5 N) and this wear effect on the disks was less evident. In [26], the average dimension of the particles was less than the half of the present ones.…”

“…The results of abrasion on the processed balls are reported in Figure 8 and Figure 9. In Figure 8, the ball volume loss Vb (mm 3 ), the wear rate u (μm/h), and the wear coefficient k are calculated as described in [26] and then reported, while in Figure 9, the roughness parameters measured on the abrasion surface of the balls are reported. It can be observed that, with increasing linear speed, the quality of abraded balls worsens when processed with Ni-Dia surfaces, while in the case of Ti-Dia surfaces, the effect of linear speed seems to improve the quality of the abraded surfaces.…”

“…Ti-Dia coatings tends to wear more than Ni diamond coatings. Unlike [26], the final roughness measurements were run after air cleaning of the disks, that is, after removal of powder debris. The final roughness can be attributed to displacing the metal coating from the diamond particles to the surrounding roughness valleys by means of a plastic deformation process.…”

“…The normal preload F N was the same for all tests, 5N, and the radius of contact between the pin and the rotation axis R t was varied (7,11, and 14 mm), while the rotational speed n was the same for all specimens at 20 rpm. A similar procedure was set up and then applied in [26], where a diamondreinforced metal matrix composite was cold-sprayed on an aluminum substrate and a synthetic diamond coating with a maximum particle size of 30 µm was electrodeposited on a cast iron substrate. The experimental campaign was carried out and the data were processed according to Archard's equations and following the procedure reported in [26].…”

“…A similar procedure was set up and then applied in [26], where a diamondreinforced metal matrix composite was cold-sprayed on an aluminum substrate and a synthetic diamond coating with a maximum particle size of 30 µm was electrodeposited on a cast iron substrate. The experimental campaign was carried out and the data were processed according to Archard's equations and following the procedure reported in [26]. In particular, the roughness was measured on the abrasive disks, and on the abraded pins (the balls) the abraded volume of the ball (volume loss) V b (mm 3 ) was measured.…”