**5. Evolution of the solutions to triboelectrochemical problems**

The choice of metals and their alloys seems to be more relevant for designing materials over plastics, foams, polymers, and natural materials if the intended application requires a limiting risk factor of deformation and flexibility, hence interest on their application to load-bearing structures. Alternatively, the development of novel metallic-glass-matrix composite materials has open up the opportunity for alloy design and innovations in new bulk metallic glass (BMG) materials to withstand deformation and flexibility that cannot be achieved by traditional metals, or casual BMGs making them attractive for various tribological systems (e.g., journal bearings), and mechanical engineering applications.

**7. Material properties, which influence surface interactions in a** 

all wear mechanisms should be referenced to the ASM standards [57, 58].

are all-technical and do not represent wear mechanisms in a scientific manner.

rates change promptly (10−15 up to 10−1 mm<sup>3</sup>

materials to be used in a wide range of operating conditions.

Fundamentally, tribocorrosion depends on the dominating deterioration mechanism of interacting surfaces in chemical environment and under relative motion conditions [10, 55]: *viz.*

Modern research has established a consensus on four main forms of wear, namely, chemical wear (i.e., corrosion and corrosive wear), adhesive wear, abrasive wear or surface fatigue wear [56]. Each process of wear obeys its own laws and, to confuse things, repeatedly one of the modes of wear acts in such a way as to affect the others, hence of the complexity of wear. Typically, there is a combination of wear mechanisms in a mechanochemical dynamic contact. In that respect, the classification of wear mechanisms remains a matter of debate among the scientific community of researchers and authors. Albeit, the terminology used by Burwell in 1957 [56] to describe wear is simple and rational, that of seeking out the primary cause of each form of wear. To avoid any further issue regarding the nomenclature in this field study,

Other forms of wear can be found in the literature depending upon the contact configuration (e.g. unidirectional and reciprocal sliding and/or rolling, rolling with slip, etc.). Wear in these contact geometries is reported to as erosion wear, fretting wear, sliding or rolling wear, impact or slurry wear, etc. This is one of the approaches that judges wear by the consequences of the conditions of a tribological contact *vis-a-vis* its environment (e.g., reactivity of tribosurfaces with the environment, the contact system configuration, etc.). Such wear descriptions

According to the recent critical review on the quantification of wear made by Meng and Ludema [55], several models have been proposed to explain various phenomena of wear. The authors have clearly enumerated 182 equations with 625 variables for explaining wear processes. This clearly shows that wear is not a material property, but rather a material system response. Wear can change drastically even as a result of a relatively small change in dynamical, environmental or material parameters forming the tribosystem. Indeed, wear

the materials are exposed to (tribological system, corrosive medium, loading contact parameters, etc.) and the choice of these materials [26, 59–61]. The combination of these two main factors, namely the operating conditions and the choice of materials, are the primary keys for monitoring the wear of materials (modes and rates) exposed to normal working conditions. Optimal solutions have been recommended as a means of meeting these requirements, are the wear maps that predict both modes and rates of wear of materials [8, 62]. A wear map or chart can be considered as one of the best descriptions of tribological/tribocorrosion conditions and as useful strategy in the design of mechanical systems (tribosystems) and for the selection of

The wear volume loss measured during or after the end of an operating tribological test provides useful information in characterizing wear. Generally, there are three typical types of

.N−1.m−1) depending upon the conditions in which

Metallic Glasses for Triboelectrochemistry Systems http://dx.doi.org/10.5772/intechopen.78233 95

**triboelectrochemical contact**

wear, corrosion, and their mutual interaction (synergism).

The ultimate resolution combining selection and material design is a consensus between economical parameters and technical qualification. Generally, this requires three essential steps, namely:


This third step in the choice of a material emphasizes the problem of economic compromise. It is thus brought to compare investment costs (resistant but expensive material) and operating costs (costs of failures, replacements, and stops they may cause). The relative weight of these two types of cost has slowly changed. The current trend is often to prefer high but predictable investment costs and to minimize operating costs when these are too difficult to predict. In addition, in a competitive economy, short-term cash optimization is increasingly being replaced by optimizing long-term profitability. In turn, this may well favor investment, especially in metallic glass alloys whose resistance to mechanical and chemical constraints (i.e., to tribocorrosion) is optimal.

In what follows, we will particularly focus on the second step above, namely the behavioral of BMG materials with regard to their wear and corrosion testing, and in particular to their mutual coupling effect (tribocorrosion).
