Deactivation Effect of Tricresyl Phosphate (TCP) on Tribochemical Decomposition of Hydrocarbon Oil on a Nascent Steel Surface

Abstract

A nascent surface has high activity to catalyze the decomposition of a lubricant under boundary lubrication conditions. To reduce the decomposition of a lubricant (multialkylated cyclopentane, MAC), tricresyl phosphate (TCP) was introduced as an additive. The tribological properties and decomposition process of lubricants on the nascent surface of bearing steel 52100 were investigated by a ball-on-disk friction tester in a vacuum chamber with a quadrupole mass spectrometer (Q-MS). The addition of TCP prolonged the induction period for decomposition of the lubricant. During the friction processes, hydrogen and gaseous hydrocarbons desorbed as tribochemical reaction products. XPS analysis revealed that the tribofilm from the additive was mainly composed of iron phosphate, which decreased the probability of generating a nascent surface, resulting in the reduction of desorption rate of gaseous products. The critical load for the mechanical activation of the decomposition correspondingly doubled.

Gaseous Tribochemical Products of Hydrogenated DLC Film and Stainless Steel Pair in Air Detected by Mass Spectrometry

“…As tribochemical products, there are large molecular hydrocarbons [15] and carboxyl-containing compounds [2], etc. The large hydrocarbons decompose due to sliding and release small molecular hydrocarbons, such as methane, ethane and propane [16], which can be detected by quadrupole mass spectrometer. The formation of C-H and C-OH not only consumes most carbon radicals which interact with the counter surface strongly, but also constructs a C-H and C-OH terminated surface which interacts with the counter surface by the weak Van Der Waals' force [17] and hydrogen bonding.…”

Friction reduction of pre-phosphating nanofilm on bearing steel by tricresyl phosphate pretreatment in boundary lubrication

“…The appearance of a minor peak at bonding energy of 287 AE 0.1 eV in Figure 9(b) serves as an evidence to indicate the bonding of carbon to the oxygen in the phosphate group. 7,18 From the XPS signal of O atomic orbit, the P element bonding state with Fe element from steel matrix can be recognized. The O 1 s signals, as shown in Figure 9(c) and (d), suggest that the occurrence of many peak spectra between bonding energy ranging from 529.8 AE 0.1 eV to 534.1 eV is in fact attributed to the existence of different valences.…”

“…The relatively insignificantly small peak at 715.1 AE 0.1 eV in the spectra for TCP disk (Figure 9(f)) implies the occurrence of Fe 2þ shake-up satellite. 7 The doublet P 2 p signal (Figure 9(g)) represents the linear superpose of 2p 1/2 and 2p 3/2 orbitals mainly resulted from the splitting of degenerate orbital. The main intensity at 134 eV is identified as caused by the phosphorus in a phosphate group.…”

Boundary and Extreme Pressure Lubrication

“…In some environments, however, e.g., vacuum, the complete destruction of a molecule can take place. A residual organic molecule, i.e., iron phosphate, is chemisorbed to the nascent surface reducing the probability of a nascent surface decomposing the hydrocarbon films [153,154]. This process is an example of catalytic decomposition of organic compounds on clean metallic surfaces.…”