Cementation and hardening allow the gear to have a tough core and a hard surface,
so heat-treated gears have better strength and wear resistance compared to non heat-treated ones. The surface hardening process improves the resistance of the gear to
shock mechanical loads and wear. In this paper, we have focused exclusively on dealing
with gear strength. We compared which gear better withstands static mechanic load
and the reasons for this. The heat treatment process was simulated in the ANSYS
program with the DANTE metallurgical package, in order to be able to predict the
distribution of residual stresses. This was the initial condition when adding mechanical
load to the gear tooth. For comparison, we simulated the same tooth that received
only a mechanical load. Such an example was also analytically recalculated. When
searching for the causes of this condition, we found that the formation of martensite
increases the compressive stresses and these, together with the shrinkage due to cooling,
create a surface layer with compressive stresses. We have seen that in any case, this
layer has an effect on better load tolerance. In the end, the analytical results deviated
from numerical ones up to 150 MPa. Given the justified reasons, such as the chosen
boundary conditions, the places of the results and the coefficients in the equations, we
concluded that they were correct. We confirmed and explained why heat-treated gears
are better than non heat-treated ones
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