In the progress
of surface engineering, it was found that due to every surface technique has
its own advantages and disadvantages, single surface treatments technique
usually cannot meet the requirements in the tribological design of harsh
working condition, which boost the development of duplex surface engineering,
defined in that two or even more techniques are used at the same time so as to
have their characteristics mutually supplemented. There is no doubt that the duplex
surface engineering is an innovative product in the period of development of
According to a research (T Bell,1998), many
advances in the field of surface engineering has grown up in the past ten
years. There are several different aspects, such as optimisation of traditional
processes (e.g. electro- and electroless plating, weld surfacing, thermal
spraying and thermochemical treatments), commercialisation of the modern
techniques (e.g. CVD, PVD, plasma thermos-chemical processes, plasma spraying
and ion implantation), developments of innovative hybrid technologies (e.g.
plasma immersion ion implantation and plasma source ion implantation) and
emergence of new coating materials (e.g. diamond and diamond-like coatings).
Despite these existing surface technologies have been designed enough practical
and been used with enhanced performance, the requirements
of servicing in a different working situation until the emergence of duplex
surface engineering has been achieved. An example of a new approach of duplex
surface engineering for Ti alloys will be discussed in this essay.
2. Issues of the
critical component of Ti alloy industrial application
development of aircraft industry, the driving force is largely dependent on the
weight-loss rate. Normally, the use of titanium alloys with light-weight
characteristics has become an important means of reducing the weight. In this
aspect, the potential applications of Ti alloy could be related to shafts,
gears and bearings. However, all of these applications involve unavoidable
issues which are mechanical joints, fluctuating loads and tribological
performance, especially the fretting in combination with fracture loads.
Obviously, these factors do limit and have the impact on the driving force of
In a previous
research (S Bhowmick,2003), the researchers attempted to coat the titanium
components with hard, low friction and thin films, such as PVD (physical vapour
deposition) deposited TiN. However, this approach was not successful because
such films could not bear high concentrated loads. On the basis of stress filed
analysis, the thin and brittle coatings could deposit on relatively soft
substrates such as titanium
Bell, T., Dong,
H. and Sun, Y. (1998). Realising the potential of duplex surface
engineering. Tribology International, 31(1-3), pp.127-137.
S., Kale, A., Jayaram, V. and Biswas, S. (2003). Contact damage in TiN coatings
on steel. Thin Solid Films, 436(2), pp.250-258.