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Journal of Minerals & Materials Characterization & Engineering, Vol. 9, No.9, pp.811-817, 2010
jmmce.org Printed in the USA. All rights reserved
Effect of Applied Load on Dry Sliding Wear Property of Aged TiNiCu Alloy
, S. Basavarajappa
, K.V. Arun
, S. Manjunath Yadav
Department of Mechanical Engineering,National Institute of Technology, Srinivasanagar,
Surathkal, Karnataka, India
Department of studies in Mechanical Engineering, University B D T College of
Engineering, Davanagere-577 004 India
Department of studies in I & P Engineering, University B D T College of Engineering,
Davanagere-577 004 India
* Corresponding Author: firstname.lastname@example.org
Titanium Nickel Shape Memory Alloy (SMA) has demonstrated its great potential for a large
variety of applications. This alloy is being actively applied to the development of new energy
conversion systems, to the design for new robots and smart material systems and to the
development of medical implants and instruments. In addition to its shape memory effect, it is
necessary to understand the wear behavior of Titanium Nickel SMA Alloys. Hence in this article
the wear behaviour of a TiNiCu+ alloy aged at different temperature have been studied against
EN 31 steel (62HRc). The results indicate that the ageing temperature greatly affect the dry
sliding wear behavior of TiNiCu alloy.
Keywords: Shape memory alloy; Ageing temperature; Weight loss; Hardness.
In the past decades, shape memory alloys are known to exhibit recoverable strains of the order of
10 percent. Out of all these shape memory alloys, near equiatomic TiNi stands as a well-known
shape memory alloy [1-3]. This is attributed to its shape memory effect. The shape memory
effect results from thermoelastic martensitic transformation. On cooling the parent B2 phase
having an ordered BCC (CsCl) structure transforms to a martensite phase possessing a
monoclinic structure of B19' type . Martensitic transformation comprises of two types namely
812 Narendranath. S, S. Basavarajappa, K.V. Arun, S. Manjunath Yadav Vol.9, No.9
thermoelastic and reversible transformations. In the former transformation, martensite starts (Ms)
to form as soon as Ms is reached and is completed below martensitic finish (Mf) temperature. In
the latter transformation, B2 to B19' can be brought about by an external stress at a temperature
above Ms. On removal of the stress, B2 phase can be recovered. As a result of the reversibility of
the martensitic transformation, near equiatomic TiNi alloys exhibit a unique mechanical behavior
termed as pseudoelasticity. With the pseudoelasticity, recoverable strain reaches up to the order
of 8 percent or even higher . The pseudoelasticity is believed to depend on many factors such
as crystal structures of the martensite and parent phase, microstructure and thermal history .
In recent years, TiNi alloy has been found to possess excellent resistance to erosion, abrasive
wear and especially to cavitation [4-9]. It showed superior performance compared with many
conventional engineering materials and commercial wear resistant materials. The high wear
resistance of TiNi alloy in addition to its shape memory effect makes it more attractive
particularly to tribologists and material scientists. Compared to conventional wear resistant
materials, hardness is not the important parameter that dominates the wear resistance of TiNi
[7, 8]. It was suggested that the high wear resistance of TiNi alloy is mainly owing to its
pseudoelasticity [6-9]. Strain hardening was also found to contribute to the wear resistance of
TiNi alloy . Liang et al  investigated the performance of TiNi alloys during sliding wear,
impact, abrasion and sand blasting erosion. They reported that TiNi alloys having higher
pseudoelasticity exhibited better wear resistance than those deprived of it. Shida et al  studied
the erosion behavior of TiNi alloys and observed that the erosion resistance of TiNi alloys was
strongly dependent on chemical composition and microstructure rather than on the hardness.
They indicated that the excellent erosion resistance of TiNi alloys might be related to
pseudoelasticity associated with the thermoelastic martensitic transformation.
In the present study, emphasis is laid on the ageing effect on wear behavior of Ti
understanding of the morphology of the wear surface and consequently, the wear characteristics
of the Ti
alloy was prepared by Vacuum Induction Melting (VIM). The prepared Ti
alloys were followed by homogenization treatment at 900°C for 5 hr. The obtained TiNi alloys
were annealed at 750°C in argon atmosphere for 45 min, followed by furnace cooling; the
alloy was divided into four groups, and aged at 350°C, 400°C, 450°C and
500°C in argon atmosphere for 45 min respectively followed by furnace cooling.
Wear tests were conducted using pin on disk wear testing machine, the disc was made with EN
31 steel having hardness of 62HRc. The wear tests were carried out on Ti
specimen of 4 mm thickness and cross sectional area of 8X8 mm
. The experiments were
Vol.9, No.9 Effect of Applied Load on Dry Sliding Wear Property 813
carried out under a constant speed of 1 m/s, constant Sliding distance of 360 meters and a track
diameter of 80 mm, with various loads of 10, 20, 30 and 40N. The responses studied were wear
losses and frictional forces. All the tests were carried out at room temperature. The
microstructure of the worn surface samples are studied with an aid of scanning electron
microscopy (SEM, JEOL-5400). The hardness was measured using Rockwell hardness testing
3. RESULTS AND DISCUSSION
The effect of hardness on ageing temperature is as shown in Fig.1. The hardness of Ti
alloys decreases with increase in ageing temperature. Addition of Cu in TiNi alloy minimizes the
formation of secondary metastable precipitate (Ti
), which may be reason for the decrease in
hardness. The hardness values were found to lie in the range 32HRc to 39HRc.
350 400450 500
Fig. 1. Hardness of aged TiNi alloys plotted against ageing temperature.
Fig. 2 shows the effect of aging temperature for (a) Wear weight loss (b) Co-efficient of friction
of aged Ti
alloys against the applied load at a constant sliding distance
360 meters and a sliding speed of 1 m/s. The wear weight loss and co-efficient of friction of
these alloys increases with the increase of normal load.
814 Narendranath. S, S. Basavarajappa, K.V. Arun, S. Manjunath Yadav Vol.9, No.9
010 20 30 40
010 20 30 40
Co-Efficient of Friction
Fig. 2. Weight Loss and Coefficient of friction of aged Ti
alloys plotted against the
Load at sliding distance of 360 m, sliding speed of 1 m/s at different aged samples. (A) Wear
weight loss (B) Co-efficient of friction.
It can be seen that wear resistance of the alloys decreases with the increase of ageing temperature
(Fig. 2) .This is because as the ageing temperature increases the hardness decreases which in turn
causes the increase of weight loss and co-efficient of friction [11-13].
Vol.9, No.9 Effect of Applied Load on Dry Sliding Wear Property 815
Failure of a material during sliding depends on its properties, the applied load and the contact
geometry. Since a material surface unavoidably consists of asperities, normal and tangential
loads are transmitted through the interacting asperities when two surfaces come into contact. It
has been demonstrated by experiments and the delamination theory that, during sliding wear
process, the subsurface undergoes plastic deformation and maximum plastic strain occurs
beneath the contact area. As the plastic strain accumulates and reaches the critical strain to
fracture, crack nucleates & then propagates, leading to eventual material removal from surface.
In general, a homogeneous material having high yielding strength, high strain-hardening capacity
and large facture strain may exhibit high wear resistance. These properties assist to reduce the
plastic strain and provide a long lifetime before the accumulated plastic strain reaches the critical
strain to fracture.
The weight loss and co-efficient of friction are found to be increasing with the increase of load.
These experimental results obey Archard’s law;
vHPKR ×= )/(………………............. (1)
Where R, K, P, H and v denote respectively, wear volume, wear coefficient, Load, hardness and
velocity. Namely, the wear rate is proportional to P, inversely proportional to hardness.
Fig. 3 shows the worn surface morphologies taken at the central region at 20N applied load for
alloy at different temperature. Usually, four main wear mechanisms adhesion,
abrasion, surface fatigue and brinelling are observed during dry sliding wear tests of TiNi alloys.
But, difference of hardness between Ti
alloys (39 Rc) and EN 31 steel (62 Rc) ensures
abrasive type of wear mechanism. The ploughing grooves (Fig. 3) illustrate the abrasive wear,
which originates from the interaction, microcutting and plastic deformation. Due to repeated
loading and unloading cycles, many surface or subsurface cracks form and eventually results in
the breakup of the surface. At the same time, Fig. 3(a) shows the wavy tracks in outer surface.
This feature is so called brinelling wear occurs from the plastic deformation of softer materials. It
should be mentioned that phenomenon of brinelling wear will increase the friction co-efficient,
but it has little contribution to weight loss.
The pearl like crests appearing in Fig. 3(c) should be ascribed to the accumulation of adhesive
junction, abrasive deformation and wear chips and the mechanical locking of surface pits. These
pearl like crests will increase the fluctuation of friction co-efficient during sliding wear process
and rapidly increase the weight loss due to mechanical fracture.
816 Narendranath. S, S. Basavarajappa, K.V. Arun, S. Manjunath Yadav Vol.9, No.9
Fig. 3. SEM micrographs of worn surface of aged Ti
Based on the experimental analysis the following conclusions are derived.
Weight loss increases with the increase of ageing temperature, this is due to decrease in
hardness of the Ti
Apart from metallurgical properties, applied load has considerable influence on wear
characteristics, the weight loss and co-efficient of friction increases with increase in the
Four main mechanisms, adhesion, abrasion, surface fatigue and brinelling are found to have
important contributions to the wear characteristics of the aged Ti
Vol.9, No.9 Effect of Applied Load on Dry Sliding Wear Property 817
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