Wear-resistant additives structure

In addition to specific properties of interest for a particular application of a material, its elasticity, compressive and tensile strength, deformability, hardness, wear-resistance, brittleness and cleavability also determine whether an application is possible. No matter how good the electric, magnetic, chemical or other properties are, a material is of no use if it does not fulfill mechanical requirements. These depend to a large extent on the structure and on the kind of chemical bonding. Mechanical properties usually are anisotropic, i.e. they depend on the direction of the applied force. 

Alloyed Iron. Tin-alloyed flake and nodular cast irons are widely used throughout the world. Estimated 1980 consumption was ca 1,200 t. As little as 0.1% tin when added to flake and spheroidal graphite cast irons in the pouring ladle gives the iron a structure that is completely pearlitic. Tin-inoculated iron has a uniformity of hardness, improved machinability, wear resistance, and better retention of shape on heating. Where pearlitic and heat-resistant cast irons are required, such as for engine blocks, transmissions, and automotive parts, tin additions may provide a suitable material. 

The ternary systems of these kinds of metals with boron reveal a more complex structure because of the presence of many other ternary phases denoted to as tp-and co-phases. The stoichiometries of these solid solutions thereof. Other ternary phases have the composition and M M B2,v, e.g., TaNiB2, Mo2peB4, and MosCoB. As an example, an isothermal section of the B-Co-Mo system is shown in Fig. 27 in which both the x- and the (p-phases are linked with Co as the binder [128], However, in systems with Fe replacing Co, a <,c-phase does not exist. Hence co is in equilibrium with liquid metal and is thus likely to form a cermet material with Fe like the x-phase Mo2Fei3Bs (Fig. 28). Phase compositions located in the pseudo-binary equilibria with a metal can easily be pressureless liquid phase sintered at temperatures between 1500°C and 1700°C. Wear-resistant parts have been developed from Mo2FeB2-Fe cermets with Ni or Cr additives [129-131, 307]. Figure 29 presents an isothermal section of the Ni-Ta-B system at 950°C [126] with three ternary phases where only X is in equilibrium with metallic Ni. 

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