Tribological properties wear process

A scratch test is an alternative to the conventional wear test to evaluate the tribological properties of polymers [75,100]. This test involves a high friction induced by a hard indenter which is pressed onto the material under load during the sliding process [51,150]. Briscoe et al. have provided a useful review about the most important theoretical models that have been developed in the field of scratching [179]. 

The material must exhibit excellent tribological properties that prevent the wear and corrosion process in which the material is removed from contacting surfaces when motion is restricted to very high frequency and small-amplitude oscillations. 

In relation with the functional properties of a part, such as fatigue and static strength, or wear and corrosion resistance, are the basis for specifying the proper process and steel as illustrated in Fig. 2 (T. Bell, 2005). The functional part properties that essentially depend on the compound layer are wear resistance, tribological properties, corrosion resistance and general surface appearance. Both abrasive and adhesive wear resistance increase with hardness and with minimised porosity of the compound layer. Porosity can be positive in lubricated machinery parts as the pores act as lubricant reservoirs. The compound layer depth has to be deep enough not to be worn away. The diffusion layer (depth, hardness and residual stress) determines surface fatigue resistance and resistance to surface contact loads. 

In order to complete the investigation of the friction reduction and antiwear processes of the colloidal additives, intrinsic tribologic properties of the antiwear films are shown as an example in Figure 4.19. The antiwear film is first established in the presence of the lubricant. After 1000 cycles the test is stopped and the lubricant is removed. The sphere and the plane are separated and carefully rinsed with light petroleum in order to eliminate all lubricant traces. After evaporation of the solvent, the sphere is applied to the surface on the wear trace and the test is restarted on the dry antiwear film. The test is stopped again and a new sphere is used to test the surface outside the wear trace. 

The field of tribology has seen a number of theoretical models for various materials and interfaces [4]. Based on these models, the formulas for the calculation of both friction and wear have been derived. Unfortunately, these equations cannot be used directly by process and equipment design engineers unless the coefficient is known. Indeed, friction and wear properties of a tribological interface depend on macro-, micro-, and nanogeometry of the... 

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