3.1 Experimental procedure

The purpose of these experiments was to obtain data for predicting the friction behaviour and corresponding friction heat division for orthogonal cutting when using coated tools. The experimental methods employed in this study are similar to those reported by the author in previous research concerning the influence of coatings on the cutting process [GRZ 99b, GRZ 98].

The experimental program consisted of several series of turning tests, which were carried out on a precision lathe equipped with force and temperature measuring systems (Figure 1).

Figure 1: Scheme of the experimental set-up (a) and force resolution in orthogonal cutting after ISO 3002/4 (b)

In this investigation the following conditions were used:

• Workpiece: thin-walled tubes of AISI 1045 carbon and AISI 304 austenitic stainless steels, 2 mm thickness, the outer diameter of the tube was varied to obtained ca. 20% increment of the cutting speed. In cuts with varying feed rate an outer diameter of 80 mm was kept.

• Tool materials: uncoated tungsten carbide P20, single-layer (TiC), two-layer (TiC/TiN), three-layer (TiC/ Al ₂O ₃/TiN) and four-layer (TiC/Ti(C, N)/Al ₂O ₃/TiN) coated inserts.

In Table 1 values of the thermal conductivity and thermal diffusivity for the tested materials at boundary temperatures, 300 K and 1000 K, are provided.

• Tool configuration: flat-faced rake, rake angle ? _o = ?5 ⁰.

• Cutting speed: v _c = 30 210 m/min.

• Feed rate: f = 0.08 0.28 mm rev ^?1. For the cutting arrangement...