**3. Application of thermal conductive paste and pads in combination with modifying coatings**

Along with the inserts of the RNGX 121200 shape, the inserts of the LNMX 301940 shape are also actively used.

The study of the process of wearing of cutting tool equipped with carbide inserts in machining wheel pair contour showed that wearing is accompanied with ductile deformation of cutting wedge of carbide tool followed by brittle fracture (**Figure 7**).

 The study mainly focused on testing carbide inserts, which were mounted in tool holders of the cutting tool assemblies. The selection of the shapes of two-way inserts was justified by the extensive use of such inserts in machining rail rolling stock products. Because of large rake angles (γ = 12–15°) and wide chip-breaking grooves, at rake face of carbide inserts (width 2.5–3.5 mm), large air cavities are formed in the contact area of bearing surfaces of the inserts and the tool holder, and the total area of their actual contact can reach up to 50–65% of the total contact area. The above fact results in significant deterioration of heat transfer from carbide insert to holder body, which is a massive heat absorber, since the air thermal conductivity is 3000 times lower than the thermal conductivity of metal of the tool holder (**Figure 8**). With this in mind, during the development of a tool system with improved heat transfer from carbide insert to bearing surface of tool holder, elastic pads of ceramic-polymeric sheet reinforced material with high thermal conductivity were mounted on. In shape and thickness, the above elastic pads corresponded to the sizes of the chip-breaking grooves of carbide inserts [8]. The used ceramicpolymer pads are characterized by high elasticity (at least 50%) and thermal conductivity of about 0.8–1.4 W/(m K), which provided a significant increase in heat transfer along the entire bearing surface of the insert by reducing air gaps between bearing surfaces of the carbide insert and the tool holder (**Figure 8b**). Due to fiber glass reinforcement, ceramic-polymer pads withstand compression of up to 40 MPa, and that guarantees reliable mounting of carbide insert. With the change of bearing surface of carbide insert, when the previous bearing surface of the insert

#### **Figure 7.**

*Chipping on the cutting insert of LNMX 301940 shape on the rake face of carbide (14%TiC, 78%WC, 8%Co) with nanostructured multilayered composite coating (NMCC) Ti-TiN-TiAlN in machining of running surface of wheel pair with ap = 6.0 mm, f = 1.2 mm, and vc = 70 m/min.* 

*Main Ways to Improve Cutting Tools for Machine Wheel Tread Profile DOI: http://dx.doi.org/10.5772/intechopen.80302* 

**Figure 8.** 

*(a) General view of the insert, and (b) contact of bearing surfaces of holder and cutting insert: 1—holder, 2 carbide insert, and 3—thermal pad.* 

 became the rake face, the remains of the pads appearing in the cutting area were easily removed by chips cutoff.
