Oxidative wear

Definition:

Oxidative wear is a type of wear that is caused on the surface of the material under non-lubricated conditions. The characteristic feature of these ear surfaces is the smooth surface and oxidative wear debris. The oxidative wear formation takes place when the surface at the sliding interface produces the wear debris and further on sliding due to an increase in the temperature this debris forms their respective metal oxides forming the oxidative wear. This type of wear is most found in the mechanical components working at very high-temperature conditions such as hot rolling etc [1]. The Fig-1 shows the oxidative wear on the copper surface. https://youtu.be/6NLtaBz-oCQ

Fig-1 Oxidative wear on the copper surface [2].

Mechanism of the oxidative wear:

The oxidative wear is mainly caused due to the oxidative film formation on the surface which is the basic feature of this wear. The oxidative film formation is mainly due to the change in temperature and working medium in the sliding interface of the material’s surface. The metallic surfaces react with the atmospheric gases to form the thin films on the surface however the films formed will be in nanometers thickness [3]. When the temperature on the surface of the materials increases over time, the film thickness of the oxidative wear also increases which reaches several micrometers causing oxidative wear [4]. The change in the oxidative film thickness with temperature v/s time is shown in Fig- 2. The oxidative film formation with the temperature changes is shown in the Fig-3.

Fig-2 Oxidative film thickness changes with temperature and time [1].

Fig-3 Oxidative wear at high temperatures [1].

Oxidative wear at high sliding speeds:

As the sliding speeds at the surfaces increases then the temperature on the surface increases which causes the formation of oxidative film and the process of oxidation is very rapid. After a period during the sliding, the oxide layers will start getting worn due to the fatigue on the surface [5]. At certain points, the temperature is so high giving rise to the formation of high spots which can be called oxide plateaux development. If there is mild wear, then these high spots get destroyed giving rise to the wear debris [6]. This mechanism of oxidative wear is shown in Fig- 4.

Fig-4 Oxidative wear mechanism with change in sliding speed [1].

In the case of the sliding speed which is under a steady state then the oxidative wear mechanism follows the same trend as the above and the mechanism is illustrated in Fig- 5.

Fig-5 Oxidative wear mechanism with change in steady sliding speed [1].

Oxidative wear at low sliding speeds:

At low sliding speeds, conditions such as high temperature or friction are not possible and hence do not form rapid oxidation. However, there will be the formation of the oxidative layer which creates the mild wear forming the wear debris. This debris will get compacted and forms the oxide islands which helps in reducing the friction on the surface. The top surface of these oxide islands consists of the oxide films which are a mixture of oxides and metals [7]. This mechanism is illustrated in Fig- 6.

Fig-6 Oxidative wear mechanism at low sliding speeds [1].

Wear debris formation in oxidative wear:

During the sliding, the interface of the surface experience a change in temperature that results in the formation of the oxide layer at the surface. This oxide layer formed will get disintegrated on a further increase in temperature due to sliding. There are formations of the oxide islands at the high points on the surface where the debris formation takes place. The interaction between the strained surface and the surface exposed to the oxide film upon continuous sliding will result in forming the wear particles due to adhesive contact. When the oxides in those regions get incorporated with the surface metal then it results in combinational wear particle which gets disintegrated from the surface interface due to the rolling effect. Thus, the wear debris with a combination of the metal and oxides will be formed at the interface creating further oxidation. This mechanism is explained using Fig- 7.

Fig-7 Formation of wear debris at oxidative wear [1].

Oxidative wear research:

There are studies based on many parameters affecting the oxidative wear on the surfaces, the parameters such as the sliding speed, temperature, oxide film formation, etc play an important role in this wear. Studying the characteristic of this oxidative wear is important for different materials to incorporate into different applications. Q.Y. Zhang et.al. studied the characteristics of oxidative wear and oxidative mild wear, they found that in oxidative mild wear the wear rate is substantially lower than the oxidative wear. The wear resistance also depends on the tribo-oxide films irrespective of the matrix [8].

Reference:

[1] Stachowiak, G.W. and Batchelor, A.W., 2013. Engineering tribology. Butterworth-heinemann.

[2] Kvačkaj, T., Kováčová, A., Bidulska, J., Bidulský, R. and Kočičko, R., 2015. New approach in the properties evaluation of ultrafine-grained OFHC copper. Archives of Metallurgy and Materials, 60.

[3] A.T. Fromhold, Theory of Metal Oxidation, Volume 1, Fundamentals, Elsevier, Amsterdam, 1976.

[4] F.P. Fehlner and N.F. Mott, Low Temperature Oxidation, Oxidation of Metals, Vol. 2, 1970, pp. 56-99.

[5] T.F.J. Quinn, J.L. Sullivan and D.M. Rawson, New Developments in the Oxidational Theory of the Mild Wear of Steels, Proc. Int. Conf. on Wear of Materials, Dearborn, Michigan, 16-18 April 1979, editors K.C. Ludema, W.A. Glaeser and S.K. Rhee, Publ. American Society of Mechanical Engineers, New York, 1979, pp. 1-11.

[6] A.W. Batchelor, G.W. Stachowiak and A. Cameron, The Relationship Between Oxide Films and the Wear of Steels, Wear, Vol. 113, 1986, pp. 203-223.

[7] J.E. Wilson, F.H. Stott and G.C. Wood, The Development of Wear Protective Oxides and Their Influence on Sliding Friction, Proc. Roy. Soc., London, Series A, Vol. 369, 1980, pp. 557-574.

[8] Zhang, Q.Y., Chen, K.M., Wang, L., Cui, X.H. and Wang, S.Q., 2013. Characteristics of oxidative wear and oxidative mildwear. Tribology International, 61, pp.214-223.