Dr ing. Hieronim Piotr Janecki 

      

TU Radom      Chrobrego 27     26 - 600 Radom  - Polen

Leiter des Labors für Computerunterstutzung in Chemie

Seit 1976  aktiv im Bereich     Reibung Schmierung und Verschleiß  


M.Janecka H.P.Janecki

TU Radom, Malczewskiego 22, 26-600 Radom Poland; janeckin@wp.pl 

Tribologically investigated surfaces in the presence of ferrocene sulphur derivatives.

Abstract Ferrocene and their derivatives – a typical organometallic "sandwich" - is very popular and finds broad application in both purely theoretical chemistry and in applied science and technology. This paper describes theoretical and practical aspects of ferrocene sulphur derivatives and their application in tribological systems. The behaviour of ferrocene is described in the theoretical part. In the practical part some aspects of the tribological action of ferrocene derivatives are described. The data obtained from practical investigations and surface analysis shows interesting interaction between ferrocene derivatives and surfaces.

Keywords: ferrocene derivatives, surface analysis, tribochemistry.

Introduction

The results of the latest investigation of materials of specific future usage, as well as a need for limiting energy losses caused by friction and wear affect the present progress in machine building. In 1966, it was estimated that approximately 30% of raw materials used in the process was being lost due to wear . The loss of materials and energy may be considerably limited when materials and lubricants in friction are appropriately chosen. Attempts to achieve the best effect made it possible to find many, but not all, solutions of the problem. The mechanical, physical and especially chemical processes which take place in a friction pair have not been fully examined and comprehensively described yet. New research concerning kinetics, friction and wear mechanisms affects durability of the surfaces of machine elements. Therefore, it is important to precisely examine the mechanisms which govern the behavior of lubricants and additives in boundary friction conditions. The object of our research is to present relationships between interactions of various chemical media in friction processes in order to characterise those processes. It is known that lubricant oils without additives are insufficient because they do not minimalise friction and wear of working elements .

The objective of the paper

The main aim of this paper is the discussion of synthesis, physical and chemical properties, and possibilities of application of ferrocene derivatives in the field of tribology, particularly in tribochemistry

Ferrocene Derivatives in Tribology

The fields in which ferrocene derivatives may be applied are as follows:

polymerisation catalysts, inhibitors of photolytic ageing of polymers, microanalytical reagents, biochemical reagents, improvers of base oils and synthetic oils [1 – 3].

Ferrocene derivatives have relatively active or labile C-O and C-S bonds. This property is interesting from the point of view of the studied effectiveness of tribological interaction of additives. The aromatic character of molecules and possibility of numerous changes in their different structures make it possible to carry out valuable and effective experiments.

Tribological Properties of Ferrocene Derivatives

The following 1,1'dialkyl-2thia[3]ferrocenophane 1SJ -4SJ have been chosen for the study, The Ferrrocene FcH means Fe(C5H5)2 see Table 1

TABLE ! The molecular structure of tested 1,1'dialkyl-2thia[3]ferrocenophane

 

 

 

1S

2S

3S

4S

In order to find the most appropriate operating conditions, the effect of concentration on the wear scar diameter was investigated on the basis of ferrocene = FcH see Fig. 1 and 3SJ. Using four-ball test (fBA) lubricating oil solution containing ferrocene (FcH) does not decrease wear while the-3SJ-1,1' diethyl2-thia [3]ferroceno- phane evidently reduces wear at the concentration higher than 0.025 mol/dm3. The working conditions were as follows:  

· ball diameter - ½” (produced according to PN-75/M-86452)

· ball material - £H-15 steel

· hardness - 62-65 HRC

· rotational speed - 1650 rpm

· sliding velocity - 0.0565 m/s

· load - 60 – 8000 N

· temperature - 293K

· friction time - 10 s

The results of ferrocene, ferrocene derivatives and di-benzyldisulphide investigations are presented in Fig. 1.

Figure 1

Concentration of additives solution c= 0.025 mol/dm3 in white oil.

The lowest wear is observed for the solution with additive 3SJ-1,1' diethyl2-thia[3]ferrocenophane, the order of increased wear is as follows:

3SJ > dBdS >2SJ>4SJ>1SJ > FcH

In the case of the investigated solutions of various additive concentrations of the compound 3SJ (see Table 1), various wear scars were registered in friction tests. The most interesting wear surface is presented in Fig.2. The SEM image reveals a wear scar as well as a transfer of material after the tribological test. The reaction layers were observed as a bright surface containing tribochemical reaction products. The frictional surface was etched by electrons in the area seen as darker surface, which does not contain tribochemical reaction sulphur products (see Fig. 2).

Figure 2

 

 

 

 

 

 

 

 

SEM image of wear scar. Reaction layer example; fBA test, load 2000N, steel £H-15, solution of 3SJ c=0.025 mol/dm3 in white oil.

Conclusion

Ferrocene derivatives modify tribological properties of lubricants. Significant relations between the molecular structure and antifrictional properties were observed. 1,1’-dialkyl 2-thia[3] ferrocenophanes show positive antifrictional action in a wide range of loads and temperatures. Introducing ferrocene derivatives into base oils makes it possible to use the derivatives at higher loads. This improvement strongly depends on the structure of the compounds being used.

1. Patent USA 4 946 609 (Veba Oel BRD) Moröl für Dieselmotoren „Anwendung von verschiedenen Eisenvermindungen (Ferrocenderivate und organische Eisensalze)”,

2. H.Janecki, M.Dominiak: "Anwendung von Radionuklidmethoden bei der Untersuchung des RSV Verhaltens Ausgewählter Ferrocenderivate" II Int. Tagung Reibung, Schmierung und Verschleiß Schloß Reinhartsbrunn 1983,

3. Janecki, M.Janecka, "Investigations of ferrocene sulphur derivatives in tribological systems", Proceedings of II International Conference Tribochemistry, Janowice 97,15 - September, p 59-66,

4. H.P.Janecki: „Ferrocene Sulphides and Boundary Lubrication” Tribologia 3/99,(165), p. 365-376,


2

 H.P. Janecki, M. Janecka

TU Radom, Malczewskiego 22, 26-600 Radom Poland; janeckin@wp.pl 
 

The basic states of surfaces and tribologically investigatet surfaces

Abstract It seems that during the last 10 to 15 years research institutions have increasingly focused their attention on synthetic and natural vegetable oils. The two groups of liquid lubricants occupy more and more space in scientific publications. Most of the publications dealing with organometallic additives discuss metal dialkyldithiophosphates. The exceptions are organometallic tin and iron compounds used in laboratory and model investigations as friction modifiers and kinematic pair surface modifiers.

The effect of lubrication on wear

Senatorski's studies have shown that there is an important influence of oil viscosity on wear rate in the conditions of analysis of wear resistance of carburized, nitrided and chromium-plated layers. The results of the investigations mentioned above generally indicated a dependence of wear rates of diffusion layers on the viscosity of the oil in which the layers were tested. One should also keep in mind adsorption – the first initial stage of lubricant - surface interaction which often determines both the type and course of friction and the character of wear changes. Both the above considerations and mathematical models are created with the aim of underlining the effect of lubricant – friction pair surface interaction on the performance of friction pairs during operation.

Testing Conditions

The tests were performed using Tribometer ZA-2. specifically for the study of additives and lubricants. Additionally, a friction pair of similar dimensions made of bearing bronze B1010 was designed. The lubricating agent was a solution of 1,1'-diethyl-2-thia[3]ferrocenophane sulphide (3SJ) of 0.025 mole/dm3 concentration in paraffin oil. The 3SJ sulphide exhibited the highest reactivity towards the surface tested. After the tests had been completed, the surfaces of the balls were analysed using an optical microscope. A wear scar of a*b 2.57 * 2.38 mm with wear volume VV = 0.7 * 10-3mm3 was recorded for a steel 100Cr6 kinematic pair at the load of 31 N.

The initial traces of reaction layers formed were observed in the polarized light under a microscope at the load of 50 N. Selected measurement results obtained for a solution of 3SJ sulphide have been given in Table 1.

Table 1 Selected results of wear measurements carried out using Tribometer ZA-2

Table 1

Load [N]

Wear V *10-3

[mm3]

m (time

1s)

m (time

3s)

10

0.24

0.2

0.07

30

0.7

0.20

0.127

50

1.3

0.19

0.128

70

2.20

0.183

0.123

90

2.40

0.177

0.122

110

2.60

0.186

0.127

Keeping in mind the division of friction conditions depending on the friction coefficient determined [1], it becomes clear that the experiments were carried out under boundary friction conditions. The formation of reaction layers and their influence on friction coefficient reduction were observed throughout the investigations. The third column in Table 2, which illustrates a change in friction coefficient within the first second of tribometer ZA-2 operation, seems to be interesting in the light of theoretical considerations.It should be noted that starting from a load of 50 N the system moves within the first second of operation beyond the boundary friction area towards dry friction *> 0.15, but within the third second it returns to the boundary friction area. And so we are back with the motto of this project "the first seconds and minutes of the friction pair's motion are the most important ones". Figs 1 – 2 show pictures of the surfaces examined, Fig. 2 gives analysis results. Reaction layers can be clearly seen non-uniformly arranged on the surfaces of the balls tested.

Figure 1 Wear scar SEM image after ZA-2 test, N = 50N, m = 0.096, t=3min

Wear scar SEM image after ZA-2 test, N = 50N, m = 0.096, t=3min, wear scar centre

A skillful design of a system that will work properly since the startup guarantees continued, successful failure-free operation. To satisfy this condition it is important at the friction pair design stage to choose appropriate materials treating lubricant as a component of the same importance as the materials selected for the kinematic pairs being designed. Currently available results of investigations of sulphur ferrocene derivatives indicate a possibility to generate mixed organic-inorganic layers on friction surfaces. Fig. 2 shows an enlarged image of a wear scar with traces of reaction products on the surface.

Figure 2 Enlarged SEM image of wear scar after ZA-2 test, N = 50N, m = 0.096, t=3min, reaction products are visible along friction path, Results of steel 100Cr6 surface analysis obtained using an EDS analyser right side.

It is assumed that a kinematic pair should be matched properly to ensure failure-free mating of its elements for as long as possible. EDS studies were carried out to analyse SEM recorded reaction layers being generated on the surface of a kinematic pair. The results are shown in Fig. 2. It is difficult to model and analyse interactions of ferrocene iron and ferrocene sulphur with a steel friction surface. It is not possible to distinguish analysed signals coming from alloy iron from those coming from ferrocene iron without using the tracer method. The work [1]shows results of Auger spectroscopy analysis of the surface of a steel ball tested by means of tribometer ZA-2. The steel surface analysis results do not contribute any essential new information that would help to develop a model. However, very large changes in the chemical composition of the steel surface analysed were found. The changes appeared when the sample surface was being etched with argon ions for 2 minutes. In comparison with the chemical composition of steel as given by Polish Standard, increased chromium and carbon contents were found after the signal coming from oxygen had faded. The model surface was changed to record the presence and to analyse the reaction products being generated on the surface in the presence of ferrocene derivatives. Bronze B1010 and copper surfaces were chosen for further investigations of ferrocene sulphides under boundary lubrication conditions.

Conclusion

The results of model friction and thermal tests lead to the conclusion that in the conditions studied there was a reaction between the sulphide tested and the surface. If there had been unreacted sulphide (C5H4)2Fe(CHC2H5)2S 1,1'diethyl-2-thia[3]ferrocenophane left on the surface, the share of sulphur and iron would have been 10.66% and 18.66%, respectively

TABLE 2 Percent share of sulphur and iron in 3SJ sulphide and on the surface

In compound

On surface

C%S

C%Fe

C%S

C%Fe

10.66

18.66

9.21

0.38%

because C%S = 9.21% < 10.66% and C%Fe = 0.38% < 18.66%. It can be concluded that a reaction layer containing less sulphur and iron than the 3SJ compound forms on the surface of the plate tested. The compounds of interest – sulphur derivatives of ferrocene – interact with the surface of the tested metal samples at a certain defined depth. The reaction layer is non-measurable if its thickness is too small. The reaction layers generated on bronze B1010 and copper surfaces by a static thermal method exhibit poor adhesion to the surface and can readily be removed with polar solvents.

Reference

1. H.P.Janecki "The ferrocene derivatives and their tribological properties” Thesis Warsaw 1989

 

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Impact factor of the journals related to tribology 

Journal/Year 2000 1999 1997 1994
Tribology Letters 1.816      
Wear 0.698 0.838 0.686  0.580
Journal of Tribology 0.643 0.751 0.408 0.427
Tribology International 0.555 0.572 0.450 0.239 
P I Mechanical Engineering Journal 0.506      
Tribology transactions 0.406 0.509 0.522  0.369 
Lubrication Engineering 0.279 0.398 0.377   0.269
Journal of Japanese Society of Tribology   0.036   0.018
Industrial Lubrication Tribology 0.020      


 

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