**1. Introduction**

Metal-matrix composites (MMCs) have higher stiffness and mechanical strength than alloys, however they have lower ductility and fracture toughness [1]. In microstructure of MMCs if a bond between particulate reinforcement and matrix has been constituted, then the composite exhibits an ability to withstand high tensile and compressive stresses. Continuous fibers, short or chopped fibers, whiskers and particulates have been used as reinforcement materials in MMCs. Discontinuous reinforcement phase composites are common due to availability, low cost, independence of mechanical properties from particulate orientation [2] and production via a vide range of manufacturing routes [3-6].

Wear is described as the removal of material from a surface in relative motion by mechanical or chemical processes [7]. The wear of the materials can be formed due to adhesion, abrasion, surface fatigue or tribochemical reaction [8,9]. The removal of material from the surface by hard particles (three-body abrasion) or by a rough counter face (twobody abrasion) is generally termed as abrasive wear. The wear resistance of a material is related to its microstructure, and the changes in microstructure may take place during the wear process [10,11] Developments of lightweight and energy-saving materials have become more numerous in the past few years in many different fields [12-16]. Recent studies [17-25] indicated that a significant improvement in the tribological properties of Fe alloys can be attained by the addition of hard carbides. Metallurgical processing, such as casting and powder metallurgy (P/M) techniques, has been successfully employed to produce antiabrasion Fe-based composites consisting of hard carbide particles [17-25]. The strength of the as-cast composites is usually less than that of the P/M composites, and it is also possible that some large casting defects exist in the cast. These problems can largely be overcome in the P/M route. Additional advantages of the P/M process are that a high dislocation density can be introduced into the matrix, recrystalization can be prevented by carbide reinforcements, and in their structure their subgrain size is small.

© 2013 Yılmaz et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Yılmaz et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Most studies [17-21] indicated that the wear resistance of MMCSs manufactured by the P/M and/or casting techniques increased with increasing volume fraction of reinforcement particulates. The wear resistance of the composite decreased with increasing reinforcement above a certain level. Jha *et al*. [26] indicated that the wear rates increased with increasing reinforcement volume fraction in the P/M sintered soft matrix alloys.

Effect of FeCr Intermetallic on Wear Resistance of Fe-Based Composites 5

Ar Ar Ar

Degassing Liquid phase sintering As solutionized

Element amount (wt %)

**Table 1.** The chemical compositions of the Fe/Cr particulates

900 1200 1100

**Table 2.** Processing schedules of the powder metallurgy Fe composites.

Sintering Sintering Solutionizing

**3. Results and discussions** 

**Figure 1.** Optical micrographs of the sample S1

**3.1. Microsturucture** 

 Cr Fe Si C P S Fe/Cr 64 26,30 1,80 6,84 0,02 0,038

Treatment Temperature (0C) Time (h) Atmosphere Remarks

1 2 2

The microstructures of the composites with FeCr reinforcement were investigated and optical micrograph of the sample S1 is given in Figure 1. It was seen that, the microstructure of the FeCr reinforced MMCSs consist of ferrite matrix with dispersed FeCr particulates. The addition of graphite to the composite with FeCr particulates formed different phases (Figure

2-Table 3). Depending on graphite amount, pearlite phase started to form around graphite particles, and increasing the amount of graphite increased the ratio of pearlite phase and M3C carbides. Graphite grains were formed in the pearlite structure in samples with 1wt% graphite supplement. On the other hand, by increasing graphite content to 2wt%, ledeburitic structure has been formed in grain boundaries besides formation of M3C carbides at grain boundaries and toward center of grains (Figure 3). The microstructures of the samples having soft copper supplement in the range 0.5-2 wt% with graphite (0.5wt%) and FeCr (5wt%) particulates were found near to each other, but their microstructures was different than the samples having a structure without copper supplement (Figure 4-5 and Table 4.).

In this study, the Fe base P/M composites are reinforced with FeCr carbide complexes, soft graphite, and Cu particles to improve wear resistance benefiting from the advantage of both the energy absorption properties of the soft matrix phases and the wear resistance of the hard carbide phases. With this aim, we investigated the microstructures, wear properties and some mechanical properties (surface hardness, tensile strength and toughness of Fe base MMCSs) by using scanning electron microscopy (SEM), surface hardness (HB), tensile testing, Charpy V-notch impact and abrasive wear tests.
