Effect of load on the friction and wear behaviour of silicon nitride and silicon nitride titanium carbide ceramic composite

Effect of load on the friction and wear behaviour of silicon nitride and silicon nitride titanium carbide ceramic composite

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Materials Today: Proceedings xxx (xxxx) xxx

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Effect of load on the friction and wear behaviour of silicon nitride and silicon nitride titanium carbide ceramic composite Shahid Manzoor ⇑, M.F. Wani, S. Shahid Saleem Tribology Laboratory, Department of Mechanical Engineering, National Institute of Technology, Srinagar, Hazratbal, Kashmir, India

a r t i c l e

i n f o

Article history: Received 5 July 2019 Accepted 20 July 2019 Available online xxxx Keywords: Friction Wear Silicon nitride Friction coefficient Composites

a b s t r a c t In the present research study, the tribological characterization of pure silicon nitride (Si3N4) and silicon nitride-titanium carbide ceramic–ceramic composites (Si3N4 + 1 wt% TiC and Si3N4 + 2 wt% TiC) was carried out under dry sliding condition. The samples of Silicon nitride and ceramic composite were fabricated through liquid sintering using yttrium oxide, aluminium nitride and optical grade silica as sintering additives. The effect of load on the friction and wear properties of Si3N4 and Si3N4/TiC composite is studied. Friction and wear tests were performed on a pin on disc tribometer at room temperature. It was observed that the friction coefficient and wear rate decreases with increase in load. Further, the Si3N4 + 2 wt% TiC composite possessed better tribological characteristics among the materials tested. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering

1. Introduction The exact prediction of friction coefficient and wear coefficient of the monoliths and composites is very difficult because tribological properties also vary with the fabrication procedure e.g. hot pressed sintered monoliths/composites ceramics bear better tribological properties than the simple sintered monoliths/composite ceramics. The relation between tribological properties like friction and wear is very complex. There is also a general myth that high friction coefficient leads to high wear. But the truth is that both the tribological properties have their own significance in accordance with the application. e.g. in case of pencil – the friction coefficient must be low and wear should be high, in case of tyres – the friction coefficient must be high and wear should be low, similar phenomenon will required in case of brake pads, now in case of dentistry – the friction coefficient [1]. Ceramics are broadly classified into oxides, non-oxides, carbides and nitrides and these classifications give a significant difference in friction and wear mechanism. Sintering is promted by adding additives to pure materials such as ceramics like aluminium oxide [2]. The mechanical and tribological properties of Si3N4 depends on the design of Si3N4 microstructure [3]. If the amount and content of extended grains are improved and furthermore they are conveniently associ⇑ Corresponding author. E-mail address: [email protected] (S. Manzoor).

ated, materials with astonishing mechanical properties but highly anisotropic are developed [4]. Si3N4 – based ceramics are likely substitute for further traditional material for these specific applications due to their high tribological properties [5]. The relation between tribological properties like friction and wear are also complex. There is also a general myth that high friction coefficient leads to high wear. But the truth is that both the tribological properties have their own significance in accordance with the application. e.g., in case of pencil – the friction coefficient must be low and wear should be high, in case of tyres – the friction coefficient must be high and wear should be low, similar phenomenon will required in case of brake pads, now in case of dentistry – the friction coefficient must be low and wear also should be low [6–8]. In tribological applications, (Si3N4) ceramics have been used as ball components of bearing system under lubricated conditions. However, the sliding contact of (Si3N4) – (Si3N4) self-mated tribopairs under dry condition produces a high friction coefficient and high wear rate because the abrasive wear is affected by the intrinsic brittle nature of ceramics [9–10]. Ceramics generally have poorer electrical and thermal conductivity. The low toughness of ceramics (brittleness) causes them to fail suddenly when the applied stress is sufficient to propagate cracks that originate at flaws in the material. The actual stress level at which this occurs can be very high if the flaw sizes are small. The materials consider for the structural components have a wide range of variety for complying the design engineer

https://doi.org/10.1016/j.matpr.2019.07.638 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering

Please cite this article as: S. Manzoor, M. F. Wani and S. S. Saleem, Effect of load on the friction and wear behaviour of silicon nitride and silicon nitride titanium carbide ceramic composite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.07.638

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S. Manzoor et al. / Materials Today: Proceedings xxx (xxxx) xxx

requirements that contain far more than the plain materials and plastics that represents traditional constructional materials. The development in these structural materials can be observed remarkable in past few decades. From the wide range of materials, engineering ceramics are known for their extreme condition applications due to high hardness, high fracture toughness, inertness, corrosion resistance, sustainability at high temperatures etc [11]. To improve mechanical properties and to increase conductivity The addition of conductive compounds such as titanium carbide (TiC), titanium nitride (TiN), and (TiB2) to Si3N4 matrices has been one approach taken [12–14]. The Present study is focused on evaluating the effect of load on the tribological properties of Si3N4 and Si3N4-TiC composites. The microstructure and hardness of the composites have also been studied. 2. Experimental

varying conditions of load from 20 N to 60 N. The test duration, stroke and frequency were kept at 45 min, 2 mm and 20 Hz respectively.

3. Results and discussion 3.1. Hardness tests Table 1 shows the value of Vickers’ Hardness for pure Si3N4 and various Si3N4-TiC composites. The indentation was carried out a load of 1kgf for a dwell duration of 10 s. It was found that the hardness of the ceramic composites was greater than that of pure Si3N4. The hardness value was found to increase proportionally with the added weight percentage of TiC. As such the highest value was observed for the composite of Si3N4 and 2 wt% TiC (19.88 ± 0.25 GPa).

2.1. Fabrication

3.2. Analysis of friction

For preparation of the base composition of monolith silicon nitride ceramic, we mixed raw Silicon Nitride (Si3N4) powder Yttrium Oxide (Y2O3) powder (>99.9% pure, Merck, India) and optical grade Silica (SiO2) powder (>99.9%, India) attrition mill (Netzsch, Germany) that was used for the mixing of the powders used for base composition, for a duration of 3 h using Isopropanol (GR grade, Merck, India) as the liquid medium and high purity Alumina (Al2O3) balls of 3 mm diameter as milling media. After mixing in attrition mill, the slurry was dried at 75 °C in an air oven for 2– 4 h for liquid isopropanol evaporation and finally, the dried mass was sieved through a 60 mesh B.S. screen for separation of milling media i.e. pure alumina balls, granulation and collected. Ceramic composite batches containing 1 wt% and 2 wt% Titanium Carbide (TiC) powder were also prepared in the same way the compositions Samples were prepared graphite resistance heating furnace shown in static nitrogen atmosphere at temperature of 1740 °C with a dwell of 2 h according to the following schedule/input given to the furnace:

Fig. 3 indicates the variation of coefficient of friction, as load is increased from 20 N to 60 N gradually, for pure Si3N4, and Si3N4-TiC composites. It is evident from the figure that the frictioncoefficient decreases as the normal load is increased from 20 N to 60 N. The lowest value of friction coefficient is attained at 60 N normal load for all the compositions. It is observed that at all load conditions, the lowest value of coefficient of friction is attained for the composite of Si3N4 and 2 wt% TiC. It can be clearly discerned that the addition of TiC to Si3N4 results in decreasing the value of friction coefficient.

i. ii. iii. iv. v.

Up to 1200 °C @ 20 °C/min Up to 1500 °C @ 15 °C/min Up to 1740 °C @ 10 °C/min up to 1740 °C for 2 h Downtown to 40 °C @ 20 °C/min

3.3. Analysis of wear Fig. 4 indicates the variation of the specific wear rate for various composites of Si3N4-TiC and pure Si3N4 with increase in load from 20 N to 60 N. The wear was acquired by mass loss of the sample, which was measured by weighing the samples before and after each of the tests with electronic balance. Specific wear coefficient (Kw) is then obtained by Archard’s wear model equation

Kw ¼

Vw ðmm3 =NmÞ Ds  P

where

2.2. Sample preparation All samples were fixed on a flat metal plate with help of epoxy adhesive and ground on both sides in a surface grinding machine using diamond grits grinding wheel for smooth surface finish. After machining all samples were kept in an oven for 2–3 h at 150 °C for evaporation and cleaning of epoxy adhesive used for fixing the samples on flat plates. Polishing of all the samples was done at constant load required to hold the samples on polishing machine using the silicon carbide grit emery paper for 2 h. After polishing on silicon carbide emery paper, the surface was further polished with the help of diamond paste of 0.5 lm and 0.25 lm till mirror surface was obtained. Further, the surface roughness was measured with the help of a profilo-meter, and the results are shown in Fig. 1. Furthermore, the microstructure of samples is shown in Fig. 2. 2.3. Friction and wear tests The Dry test for friction and wear measurement, were performed on a pin-on – tribometer at room temperature under

Kw = Specific wear coefficient (mm3/Nm) Vw = Wear Volume (mm3) Ds = Sliding Distance (m) P = Normal Load (N) It is evident from the figure that the specific wear rate of pure Si3N4 and various compositions of Si3N4-TiC shows a decreasing trend with rising normal load. The greatest values of specific wear rate for all compositions was attained at a regular load of 20 N, whereas the lowest value of the specific wear rate was attained at a normal load of 60 N. It can also be discerned from Fig. 4 that the addition of TiC to Si3N4 results in reduced specific wear rate. The lowest value of specific wear rate for each load condition is observed for the composite of Si3N4 and 2 wt% TiC. As such the lowest specific wear rate is attained at 60 N for Si3N4-2 wt% TiC. The reduction in specific wear rate with the addition of TiC to Si3N4 can be attributed to the increase in hardness of the composites as TiC is added to Si3N4 as is observed in Table 1. As a result of higher hardness values, the wear rate of Si3N4-TiC composites shows a decreasing trend.

Please cite this article as: S. Manzoor, M. F. Wani and S. S. Saleem, Effect of load on the friction and wear behaviour of silicon nitride and silicon nitride titanium carbide ceramic composite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.07.638

S. Manzoor et al. / Materials Today: Proceedings xxx (xxxx) xxx

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Fig. 1. Surface roughness of discs is given in (a-b), surface roughness of ball is given in (c-d).

Fig. 2. scanning electron microscope image: (a) pure silicon nitride, (b) silicon nitride + 1 wt% tic.

Table 1 Vickers hardness composites.

of

Si3N4-TiC

Sample

HV1 (GPa)

Pure Si3N4 Si3N4 + 1 wt% TiC Si3N4 + 2 wt% TiC

15.69 ± 0.49 17.45 ± 0.74 19.88 ± 0.25

4. Conclusion The l tests were conducted on pure Si3N4 and Si3N4-TiC composites, under dry sliding conditions, at normal loads of 20 N, 30 N, 40 N, 50 N and 60 N. Following conclusions were drawn out from the study:

 The addition of TiC to Si3N4 resulted in increasing the hardness of the ceramic composites. The hardness tends to increase proportionally with the added weight percentage of TiC. The greatest value of hardness was attained for the composite of Si3N4 and 2 wt% TiC.  The friction coefficient shows a decreasing trend with increasing load for pure Si3N4 as well as Si3N4-TiC ceramic composites. The lowest value for each ceramic was attained at a normal load of 60 N.  The addition of TiC to Si3N4 resulted in reduced value of the friction coefficient. This reduction varies proportionally with the increasing weight percentage of TiC. The lowest value of friction coefficient at each load condition was attained for the composite of Si3N4 and 2 wt% TiC.

Please cite this article as: S. Manzoor, M. F. Wani and S. S. Saleem, Effect of load on the friction and wear behaviour of silicon nitride and silicon nitride titanium carbide ceramic composite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.07.638

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 It was observed that with the addition of TiC to Si3N4, the specific wear rate of the ceramic composites decreases. This reduction varies proportionally with the increasing weight percentage of TiC. The lowest value of the specific wear rate at each load condition was attained for the composite of Si3N4 and 2 wt% TiC. The reduction in specific wear rate can be recognized to the increase in hardness of the composite with the addition of TiC.

References

Fig. 3. Comparison of friction coefficient for normal load tests for pure Silicon Nitride, Silicon Nitride 1% TiC and Silicon Nitride 2% TiC.

Fig 4. Comparison of specific wear rate for normal load tests for pure Silicon Nitride, and Silicon Nitride 1% TiC and Silicon Nitride 2% TiC.

 The specific wear rate for pure Si3N4 and Si3N4-TiC ceramic composites was found to reduce as the load is improved. The lowest specific wear rate is observed at a normal load of 60 N.

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Further reading [15] Wani, M.F. Prakash, B. Das, p.k. Raza S.S., Mukerji, J. Am. Ceram. Soc. Bull., 76 (8), 65–69.

Please cite this article as: S. Manzoor, M. F. Wani and S. S. Saleem, Effect of load on the friction and wear behaviour of silicon nitride and silicon nitride titanium carbide ceramic composite, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.07.638