Solution Combustion Synthesis of Calcium …
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± 0.3 and 4.48 ± 0.2 μm respectively. The higher surface roughness values indicate
more of partially melted regions and less of fully melted regions in the coating. The
obtained surface roughness values of HAp coatings match well with the reported
literature values (5.30–.49 μm) [51].
The Young’s Modulus of HAp coatings were determined from indentation loaddisplacement data on the cross-section of the coatings using 10 mN. The substrate
and plasma sprayed HAp coatings a1 and a2 exhibited Young’s modulus of 133, 117
and 108 GPa respectively and these values are corroborating well with the literature
values [48].
4.8 Wear Studies in Simulated Body Fluid (SBF) Medium
Reciprocating wear testing was carried out for Ti-6Al-4V substrate and plasma
sprayed coatings in order to estimate the coefficient of friction and wear loss by
employing loads of 1N, 2N, 5N and 7N. It was observed that the wear losses for the
plasma sprayed coatings were found to be less at lower loads 1, 2 and 5N and at higher
loads, the coating peeled off. The coating (a1) could withstand 7N load and then the
coating peeled off whereas the coating (a2) could withstand 5N load and the coating
peeled off at higher load (Fig. 11). This shows that the coating (a1) contained more
of the fully melted region. The coefficient of friction (COF) was found to be lower
for the coating obtained by the powder calcined at 900 °C at 1N load but with the
increase in the load, the COF matched the COF of the substrate (Fig. 12). In general,
the COF was lower for HAp coatings compared to the substrate at lower loads and
at higher loads, the coating peeled off and thus resulting in COF equivalent to that
of the substrate. The wear rate of coating a2 was higher than coating a1 (Table 3).
5 Conclusions
In the past decade, research efforts were focused on the development of hydroxyapatite powders and coatings exhibiting optimal osseointegration along with required
coating thickness, phase composition, crystallinity, porosity, adhesion, residual
stress, etc. It is evident that there is a need for careful engineering of hydroxyapatite coatings by optimizing the plasma spray parameters. The solution combustion method is a versatile and facile method for the synthesis of plasma sprayable
grade hydroxyapatite powders. The present study has confirmed the expediency of
preparing plasma sprayable powders by a single-step solution combustion method
by employing the mixture of fuels and the biocompatibility of the developed plasmasprayed HAp coating. However, there is a need for further optimizing the synthesis
conditions of SCS to obtain phase pure HAp coatings with higher crystallinity and
better phase purity.
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± 0.3 and 4.48 ± 0.2 μm respectively. The higher surface roughness values indicate
more of partially melted regions and less of fully melted regions in the coating. The
obtained surface roughness values of HAp coatings match well with the reported
literature values (5.30–.49 μm) [51].
The Young’s Modulus of HAp coatings were determined from indentation loaddisplacement data on the cross-section of the coatings using 10 mN. The substrate
and plasma sprayed HAp coatings a1 and a2 exhibited Young’s modulus of 133, 117
and 108 GPa respectively and these values are corroborating well with the literature
values [48].
4.8 Wear Studies in Simulated Body Fluid (SBF) Medium
Reciprocating wear testing was carried out for Ti-6Al-4V substrate and plasma
sprayed coatings in order to estimate the coefficient of friction and wear loss by
employing loads of 1N, 2N, 5N and 7N. It was observed that the wear losses for the
plasma sprayed coatings were found to be less at lower loads 1, 2 and 5N and at higher
loads, the coating peeled off. The coating (a1) could withstand 7N load and then the
coating peeled off whereas the coating (a2) could withstand 5N load and the coating
peeled off at higher load (Fig. 11). This shows that the coating (a1) contained more
of the fully melted region. The coefficient of friction (COF) was found to be lower
for the coating obtained by the powder calcined at 900 °C at 1N load but with the
increase in the load, the COF matched the COF of the substrate (Fig. 12). In general,
the COF was lower for HAp coatings compared to the substrate at lower loads and
at higher loads, the coating peeled off and thus resulting in COF equivalent to that
of the substrate. The wear rate of coating a2 was higher than coating a1 (Table 3).
5 Conclusions
In the past decade, research efforts were focused on the development of hydroxyapatite powders and coatings exhibiting optimal osseointegration along with required
coating thickness, phase composition, crystallinity, porosity, adhesion, residual
stress, etc. It is evident that there is a need for careful engineering of hydroxyapatite coatings by optimizing the plasma spray parameters. The solution combustion method is a versatile and facile method for the synthesis of plasma sprayable
grade hydroxyapatite powders. The present study has confirmed the expediency of
preparing plasma sprayable powders by a single-step solution combustion method
by employing the mixture of fuels and the biocompatibility of the developed plasmasprayed HAp coating. However, there is a need for further optimizing the synthesis
conditions of SCS to obtain phase pure HAp coatings with higher crystallinity and
better phase purity.