If highstrength and lowwear coatings are used in machining structural materials, the performance of cutting tools made from highspeed steel or hard alloys may be significantly improved. However, standard coatings are inadequate when machining special materials (titanium alloys, lowmagnetic steel, high� strength cast iron, etc.) or in complex loading condi� tions (for example, discontinuous cutting, alternating loads). To select the best means of improving tool perfor� mance, we need a large range of options. In particular, it is helpful to have a range of manufacturing technol� ogies for tool materials. Effective technologies may be selected on the basis of the hardening mechanisms in the tool materials. The structure of the cutting system may also be taken into account in regulating the loss of perfor� mance of the tool and the machine tool's elastic sys� tem. The cutting system includes three types of links: a mechanical link between the tool, the blank, and the machine tool; a direct link between the machine tool (the dynamic characteristics), the cutting zone (the processes in this zone), and the cutting tool (its work� ing life); and an inverse link between the tool, the cut� ting zone, and the machine tool. This cutting system may be regarded as consisting of interrelated objects, where the state of each one affects the other objects and the output parameters. In this approach, the tool performance is an integral parameter, corresponding to a set of processes and phenomena characterized by interaction of the objects within the cutting system. Consequently, it is impor� tant to know which processes and phenomena deter� mine the tool performance in ensuring the reliability of the cutting system. They are shown in general form in Fig. 1. primarily the processes at the frictional surfaces; the mechanisms of chip formation and tool wear and fail� ure; and the static and dynamic stability of the equip� ment. The block diagram in Fig. 2 illustrates output� parameter control of the cutting system by means of the input parameters. Most of the available means of control involve hardening of the cutting tool. We now consider individual means of improving tool performance by modification of the tool mate� rial—for example, by preparing the surface for coating application. Improvement in tool performance involves selecting the coating structure, the coating material, its method of application, and its treatment so as to eliminate defects. We will confine our analysis to three stages: selec� tion of the treatment of the basic tool; selection of the material, structure, and method of application of the coating; and selection of the coating treatment. Treatment of the tool base must be regarded as a means of improving the initial state of the tool mate�