17-04-2014, 04:38 PM
Thermal analysis in coated cutting tools
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ABSTRACT
This work studies the heat influence in cutting tools considering the variation of the coating thickness and
the heat flux. K10 and diamond tools substrate with TiN and Al2O3 coatings were used. The numerical
methodology utilizes the ANSYS® CFX software. Boundary conditions and constant thermo physical
properties of the solids involved in the numerical analysis are known. To validate the proposed methodology
an experiment is used. The TiN and Al2O3 coatings did not show satisfying results during a continuous cutting
process. It showed a slight reduction in the heat flux for the 10 (μm) TiN and Al2O3 coatings.
Introduction
A large amount of heat is generated in machining processes as well
as in other processes in which deformation of the material occurs.
Heat is a parameter that strongly influences the tool performance
during these processes. One way to increase the tool life consists of
coating its cutting surface with materials that provide minor wear
with thermal isolation features.
An important investigation is the study of the influence of cutting
tool coatings on heat transfer and friction wear, resulting in a
distribution of the cutting temperature both on the chip and on the
tool. It may be observed in literature that most orthogonal metal
cutting simulations were designed for uncoated cemented carbide
tools and that now an opposite trend has considered the use of
single and multiple coatings.
Numerical validation
A study about the influence of mesh refinement on the temperature
results was carried out. The analysis of the numerical mesh convergence
was done by using the following thermal properties of the ISO K10
12.7 (mm) × 12.7 (mm) × 4.7 (mm) cemented carbide cutting tool
(Fig. 3a): k = 43.1 (W m− 1 K− 1), Cp = 332.94 (J kg− 1 K− 1), and
ρ= 14,900 (kg m− 3). The convergence test analyzed different dimen-
sion meshes, and their influence on the temperatures calculated by the
numerical model was verified. In the majority of the studied cases, to
obtain the results in this present work, the number of nodes utilized was
501,768 and the number of hexahedrical elements was 481,500.
The following parameters were used in all mesh tests: time
interval of 0.22 (s), equal initial and ambient temperature at 29.5 (°C),
constant and equal heat transfer coefficient at 20 (W m− 2 K− 1), total
time of 110 (s), and area subjected to heat flux of 108.16 (mm2).
Conclusions
The following conclusions may be cited regarding the numerical
results obtained for the thermal model of heat transfer in coated
cutting tools:
1) The studies carried out during the execution of the work showed
that for a uniform heat source varying in time, considering a
constant contact surface on the chip-tool, the temperature on the
tool may be slightly influenced by the coatings when the thermal
properties of the coating are very different from those of the
substrate, even for fine 1 (μm) coating.