Thermal modelling of the friction surfacing process
The use of friction energy to deposit metals in the solid phase on a substrate, called
Friction Surfacing, is typically used to provide hardfacing and corrosion resistant coatings. The
process involves rotating a rod under pressure onto a moving substrate and a coating is
generated from the rod material at the rubbing interface. The complex events occurring during
the process have so far been studied only on flat surfaces with constant geometry. The
introduction of standard machine tools in the friction surfacing process has allowed applications
using complex shapes. This work aimed at developing new thermal models in order to control
the parameters of the friction surfacing process for new applications.
It was postulated in this work that the thermal events in the process have to be
modelled in order to control the temperature of the bond between the coating and the substrate.
Consequently the development of a three dimensional transient thermal model was undertaken.
It was identified that the thermal response of the process is directly linked to the shape of the
substrate below the rod. As the considered applications for the process involved non-uniform
shapes of substrates, the finite volume method was chosen to build this model, which was
integrated into a control algorithm.
In order to simplify the model, new studies of the rod were undertaken. Analytical and
finite volume methods were used and important results linking the dimension of the rod to the
process parameters were established. These models were evaluated against experimental data.
New ways of representing the rod that simplified the modelling of the friction surfacing process
Using the results from these studies, a new transient thermal model of the friction
surfacing process was created, based on the finite volume method. Experimental runs were
simulated and, by comparison with experimental data, the accuracy of the model was
established. The different assumptions that were made during the design of this model were also
Using the model, an iterative calculator was designed to predict the machine
parameters for new shapes allowing a constant bonding temperature to be maintained and
producing a trajectory for the rod. The error in this prediction was calculated, and it was shown
that great accuracy is required in the measurement of the real bond temperature in order to
minimise prediction errors.