Effect of Applied Load and Surface Roughness on the Tribological Properties of Ni-Based Superalloys Versus Ta2AlC/Ag or Cr2AlC/Ag Composites

Abstract

The novel Ta 2 AlC-20 vol.% Ag (TaAg) and Cr 2 AlC-20 vol.% Ag (CrAg) composites were tribologically tested versus a Ni-based superalloy Inc718 (SA) by dry sliding at a sliding speed of 1 m/s at room temperature in air at loads from 3 N to 18 N. The TaAg composites were also tested at 8 and 18 N at 550°C, and at a 3 N load against the SA with different surface roughnesses at 26°C and 550°C. At room temperatures, the coefficients of friction, l's, decreased from *0.8-0.9 to *0.3-0.4 for both the TaAg and CrAg composites as the applied normal force increased from 3 N to 8 N. Further increases in load to 18 N did not change the l's. The specific wear rates, sWR, increased with increased loads for the TaAg composite; they remained almost unchanged for the CrAg composite. This behavior was attributed to the formation of glaze tribofilms-similar to ones observed previously in these tribocouples at elevated temperatures and 3 N-promoted by the increased loads. Preconditioning of the SA surface by sliding against the TaAg composite at 550°C and 8 N resulted in l's of \0.2 and sWR \ 10 -6 mm 3 /N-m in subsequent room temperature sliding at 3 N. Somewhat higher, but stable room temperature l's of *0.3 and sWR of *3 9 10 -5 mm 3 /N-m were observed when the TaAg composites were slid versus a sandblasted SA surface at 500°C and 3 N. It follows that in situ preconditioning of the tribo-surfaces is a powerful tool for improving the properties of the MAX/Ag-SA tribocouples. The relationship between sliding conditions, chemistries of tribofilms, and their properties are discussed.

The correlation between structure, multifunctional properties and application of PVD MAX phase coatings. Part I. Texture and room temperature properties

“…Attempts have been made to develop wear-resistant composites by incorporating hard particles such as SiC [348], Al 2 O 3 [349,350] or Ag [19,[351][352][353] into the MAX phase matrix. This approach was found to be effective in reducing the wear rate.…”

Processing of MAX phases: From synthesis to applications

“…An exhaustive review was published by Gupta et al, 26 who also performed several investigations. 107,108,109,110 In general at room temperature, the wear rate (WR) was relatively high and almost linearly dependent to sliding distance, meanwhile the initial µ was low (< 0.2) but increased rapidly to larger values (>0.4). Certainly, the tribological response depends on several factors of the microstructure (grain size, purity, porosity, etc), the counter-body (metal, ceramic, hardness, etc), and the testing conditions (temperature, atmosphere, velocities, pressure, lubrication, etc).…”

“…However, the results reported later in polycrystalline samples have less attractive values. An exhaustive review was published by Gupta et al, 26 who also performed several investigations 107,108,109,110 . In general at room temperature, the wear rate (WR) was relatively high and almost linearly dependent to sliding distance, meanwhile the initial µ was low (< 0.2) but increased rapidly to larger values (>0.4).…”

Synthesis of high purity Cr2AlC nanolamellas with improved tribological properties for oil-based additives

“…In addition, it was found that Cr 2 AlC has an excellent tribological property, especially at elevated temperatures. [28][29][30] The relatively low coefficient and wear rate are attributed to the amorphous or nanocrystalline tribolms form on both contact surfaces. However, to the best of our knowledge, little work focused on the tribological properties of Cr 2 AlC as lubrication additive.…”