Load wear index

At the end of each interval the average scar diameter is recorded. Two values are generally reported— load wear index (formerly mean Hertz load) and weld point. 

From this test, antiwear and extreme-pressure data were determined, such as welding load, load wear index and wear scar diameter under a load of 40 decanewtons (daN), 60 daN and 80 daN, respectively. First, evaluations were performed on the three original nonmodified hard-core RMs, then evaluations were performed on the sulfur-functionalized ones. Four-ball test data (results only for one concentration 10 wt% additive) are summarized in Table 3.9 (Delfort et al., 1995 and 1999) for ... 

Modified hard-core RMs by phosphosulfurized compound. Improved extreme-pressure and antiwear properties have also been obtained with the introduction of some chemical species, such as sulfur, phosphorus or boron derivatives, into the colloidal core (Delfort et al., 1998 Inoue, 1993 Inoue and Nose, 1987). Welding loads, load wear index and wear scar diameter at 5 wt% of a CaC03 core surrounded by a calcium alkylaryl-sulfonate surfactant shell, and modified by phosphosulfurized calcium carbonate core were evaluated for calcium dialkyl dithiophosphate (CaDTP) and calcium trithiophosphate (CaTTP) with the four-ball extreme-pressure test (ASTM D2783 standard method). Both modified products exhibit improved extreme-pressure performances (welding load and load wear index), while their antiwear properties (wear scar diameter) compared to those of the original micellar substrate remain at least at the same level. 

Welding loads and load wear index at 5 wt% concentration (as the extreme pressure performances) are improved compared to those of the original non-phosphosulfurized substrate (Delfort et al., 1998). The welding load (daN), wear load index (daN) and wear scar diameters (mm) under a load 60 daN behavior are... 

Medium Welding load (daN) Load wear index (daN) Wear scar diameter (mm)... 

Test which is used to determine the relative wear-ball preventing properties of lubricants under boundary test lubrication conditions. Two values are reported - load wear index and weld point from two procedures EP test ASTM D 2596 and wear test ASTM D2266. There are four steel /2-inch balls. Three of the balls are held together in a cup filled with lubricant while the fourth ball is rotated against them. Resistance to motion. 

When tested in the four-ball machine, solutions of sulfur in petroleum oils of moderate viscosity or in white oil raise the critical load for the onset of severe, destructive wear, which is designated as "antiseizure" action in the technological idiom of the four-ball test. Davey [54] found a significant increase in the critical initial seizure load from 834 N (85 kg) for a petroleum base oil to 1275 N (130 kg) for elemental sulfur dissolved in the oil. Sakurai and Sato [55] observed a 3.2-fold increase in the load-wear index (mean Hertz load) for a 0.5 weight-percent solution of elemental sulfur relative to that of the uncompounded white oil. The load-wear index is a specialized result of the four-ball test that can be taken as indicative of the average antiseizure behavior of the lubricant. Mould, Silver and Syrett [56] reported a load-wear index ratio of 3.08 for 0.48% sulfur in white oil relative to that of the solvent oil, and also an increase in the initial seizure load from 441 N to 637 N (45 kg to 65 kg) and in the 2.5-second seizure-delay load from 490 N to 833 N (50 kg to 90 kg). 

TWI = Taber Wear Index. CS-10 abraser wheels, 100 gram load, determined as average weight loss per 1000 cycles for total test of 6000 cycles. 

Forbes and Silver [40] published data directly comparing the alkyl ester tri-n-butyl phosphate and the aryl ester tricresyl phosphate. Table 11-13 shows the details of this comparison as well as wear data for the acid ester di-n-butyl phosphate. The wear/load index and the initial seizure load show substantially no discrimination between tributyl phosphate and tricresyl phosphate and very little advantage of the compounded oil over the base oil. The low-load wear test distinctly shows better performance with tricresyl phosphate. The data for di-n-butyl phosphate are at variance with the hypothesis that hydrolytic degradation to the acid ester is the first step in the antiwear action of neutral phosphate esters. On the other hand, Bieber, Klaus and Tewksbury [41] separated acidic constituents from commercial tricresyl phosphate by preparative chromatography, and on blending these constituents back into the original tricresyl phosphate at various concentrations they observed enhancement of antiwear action in the four-ball test, as shown in Fig. 11-7. It should be noted that Bieber et at. worked with only 0.051% phosphorus in the lubricant, which may explain the sensitivity they observed to acid impurities. 

Systematic data on the relation between chemical structure or reactivity of chlorine compounds and lubricant additive performance are sparse. Table 11-11 gives some four-ball test data obtained by Mould, Silver and Syrett [35], with the additives listed in order of increasing effectiveness in terms of the wear/load index. The results show numerous departures from expectations based on chemical structure. For example, there is practically as much difference between the wear/load indices for the two primary chlorides, n-hexadecyl (16.2 kg) and n-hexyl (30.4 kg), as for n-hexyl chloride and t-butyl chloride (46.1 kg). A large difference would be expected on the basis of chemical reactivity between the additive effectiveness of primary and tertiary alkyl chlorides, but only a small difference for the two primary aliphatic chlorides. The overall trends are what would be expected in general, primary and aromatic chlorides are less efficacious than secondary chlorides, which in turn... 

The work of Forbes and Battersby [46] is an integrated study of the relations among the chemical structures of the dialkyl phosphites, their adsorption on and reaction with iron, and their behavior in four-ball bench testing of lubricant additive effectiveness. The four-ball data in Table 11-17 for solutions of additive in white oil show that both the wear/load index (mean Hertz load) and the initial seizure load are critically responsive to concentration, with a strong effect when the concentration increases from 0.01 to 0.04 molal (0.031% to 0.124% P). The initial seizure load is an uncomplicated criterion with a straightforward interpretation, whereas the wear/load index is contrived, both in concept and performance. The low-load 50 minute wear data show inconsistencies in the influence of additives that have not been explained. 

The influence of the metal ion is seen in Fig. 11-12, which shows low-load four-ball wear data by Allum and Forbes [58]. The results fall into three broad groups low wear levels associated with the ions Zn, Cd" , Ni, Fe " and Ag" " intermediate wear with Pb" , Sn" , and Sb" " " high wear with Bi . Where direct comparison for the effect of alkyl groups are available, they show the ester of the secondary alcohol 4-methylpentanol-2 has a stronger antiwear function than the ester of n-hexanol, except for the nickel salts. No consistent trend on which to base an acceptable explanation for the additive action of these phos-phorodithioates was observed in the data for the wear/load index (mean Hertz load). 

Figure 11-14. Cooperative additive action of t-octyl chloride and di-t-octyl disulfide. Four-ball test 10 seconds at 1750 rpm. Additives in white oil and wear/load index A. 9.1% Di-t-octyl disulfide, 2.08% S 48.0 kg. B. 8.52% t-Octyl chloride, 2.05% Cl 51.9 kg. C. 4.55% Di-t-octyl disulfide + 4.53% t-octyl chloride, 1.06% S, 1.00% Cl 81.0 kg. D. 9.1% Di-t-octyl disulfide + 8.52% t-octyl chloride, 2.1% S, 2.0% Cl 112.1 kg. Data by A. Dorinson [38].

Additive (conc.S or Cl) (a) Wear/load index, kg Intitial seizure load, kg... 

FIGURE 8.9 Wear resistance index versus carbon black loading and surface area (from Sone, 1999). 

Auxiliaries are similar to those used for - lubricants and are added to protect the metal surface from damage, such as extreme pressure additives (EP) for heavy loads and fatty acid derivatives for lighter loads (anti-wear additives). Fatty acid salts and sulfonates are corrosion inhibitors, while sulfonates and amines act as dispersants to prevent deposits. Viscosity index improvers based on polymethacrylates of - fatty alcohols reduce the temperature sensitivity of viscosity and lower the pour point. 

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