A Presentation On

1. A Presentation On Micro-structural & mechanical properties of Al2O3-TiO2 Reinforced Hydroxyapatite Coating on 316L Stainless Steel

2. Introduction • Chemical formula of HA is Ca10 (PO4)6(OH)2 • HA has similar chemical composition and crystal structure as in bonny tissues. • Which facilitates bone substitution and reconstruction.

3. When HA coated specimen uses as bio-implant than bone tissues easily grow in HA due to similar chemical composition. • Biocompatibility is assured by HA coating while... • The mechanical properties is provided by metal substrate such as tensile strength.

4. Chemical similarity of HA with different body elements

5. Why plasma spray is used? • Plasma spray is only technique which is allowed for biomedical coatings by Food and Drug Administration(FDA),USA. Because of Good adhesion strength, better biocompatibility and crystalline nature of coating. • But its disadvantage is due to high temp. of plasma jet HA changes into amorphous phases like TCP, TTCP, which is undesirable because they easily soluble in blood plasma and no contribution in biocompability.

6. How coating deposited? • The HA powder particles are fed into plasma flame by the carrier gas. • This flame propelled them towards the substrate, and during travelling the particles are melted. • And than HA particles which are completely or partially melted rapidly solidified when impinging the cool substrate.

7. Why reinforcement is required? • HA has brittle nature due to this it cant be used at highly loaded places such as Femoral and tibial cortical bones and not stable on metal substrate. • Means it is required to improve mechanical stability of HA coating. • So many time SiO2, Zr2O3, TiO2, Al2O3 are added in HA. • In this study Al2O3- TiO2 are reinforced in HA coating • So TiO2 increases strength of coating, and Al2O3 increases bio-compatibility of coating.

8. Micro-Hardness test • Porosity measurement • Surface roughness measurement • Crystallinity measures • Wear measurement • Tensile testing of Coating

9. Micro-hardness of HA • Micro-hardness is slightly increased due to reinforcement. • It measures by Vickers indenter method • In this Vickers pyramidal diamond indenter is used • Micro-hardness is higher at coating than metal specimen.

10. Indentation in micro-hardness test

11. Porosity measurement • Pores are covered by red colour. So ratio of area covered by red and total area is called porosity • Porosity was found about 7 %. • And porosity of coating cross section is higher than the coating surface. • Porosity should be minimum otherwise substrate ion degraded by blood plasma easily. And it causes adverse effect in blood plasma. • It was measured by ASTM standard B 487.

12. Porosity Test

13. Surface roughness effects • Cellular adhesion: Cell bonding with coating surface • Detachment strength: shear stress required to detach the adherent cell from the surface • Proliferation: cell growth includes cell division and cell development both. • These are surface roughness sensitive properties and increases with surface roughness is increased.

14. Surface roughness measurement • Surface roughness of the HA samples was measured by profilometry using a Mitu-loyo SurFest SJ-400 profilometer. Two or three readings were taken from each place. • In this only a marginal improvement was found after heat treatment.

15. Crystallinity measurement • Crystallinity is measured by XRD pattern . • In this present study it was studied the different amorphous phases. And according to that it was reported that crystallinity was improved after heat treatment.

16. Wear measurement • Than wear test was done by sliding test. Sliding tests were conducted using ball-on-disc tribometer (TR-201E-M2, DUCOM Instruments Pvt. Ltd., Bangluru, India). • The HA coated samples (disc) were subjected to dry sliding in ambient conditions (28± 5oC Temp., 50 ± 5% RH), against commercially available steel balls of 6.35 mm diameter. • The disks were rotated at 500 rpm against stationary steel balls at 6 mm track diameter at 5N and 10N load. And testing time was 10 minutes for each sample. Samples were mounted on the machine with the help of adhesive. • The frictional behaviour was analysed using online data of co-efficient of friction (COF). surfaces of worn samples was analysed. Depth and width of the worn wear track was measured and wear calculation was done by following formulaes: Wear volume = (2π x wear track radius). (Track width). (Maximum depth) Wear rate = Wear volume / (sliding distance X Load)

17. SEM image of Wear Track

18. Tensile test • Specimen was 316L SS on which HA coating was deposited by plasma spray process. Specimen was prepared for tensile test. Coated sample which has dimensions of 60mmx10mmx5mm was used as a tensile test specimen. Than one other bare material specimen was taken for test which has same dimensions as that of coated sample. A 3mm diameter hole was drilled in both the samples. • After that both the samples were bonded using high strength BONDTITE compound by overlapping one another making as a lap joint of 10 mm x 10 mm. Samples were tested on Tensile Test Machine (Hounsfeild, U.K.) which was S series H25K-S machine having capacity 25kN fitted with ASTM E8.

19. Comparison of porosity, roughness and microhardness during varios conditions

20. XRD Analysis • In this XRD pattern it is shown Al2O3 and TiO2 peaks. • We add only 2% Wt TiO2 and we found it in coating. • Due to small size compared to HA particle its decreases the porosity of coating • So blood plasma have less toxic effect of metallic surface means substrate surface cant be contacted with blood plasma.

21. XRD Analysis

22. Some non-favourable phases found in XRD pattern before heat treatment

23. XRD pattern after heat treatment showing higher crystallinity no TTCP was found

24. Difference in XRD pattern after heat treatment • No TTCP phase was found which has major peaks in case of without heat treatment • No change in TCP phase was found means peaks are same as without heat treatment. No change in quantity of TCP phases.

25. EDS showing Al2O3and TiO2 in coating

26. EDS showing Ca & P oxides at coating surface

27. SEM image showing reinforced particles and oxides of Ca & P taking from EDS

28. Effect on wear due to variation in load applied

29. Friction profile showing difference in 5N and 10 N loads When Applied load was 5N Applied load was 10N

30. What wear profiles shows • In case of 5N load COF is decreased up to 600 seconds and after that it was slightly increased. It was remained below 0.1. it shows lower friction rate at lower loads. • And at 10N load wear rate was higher and COF was increasing with time and always above than 0.1.

31. Effect on wear due to heat treatment

32. Friction profiles in case of with or without heat treat ment Without heat treatment load was 10 N With heat treatment for 1 hour load was same as 10 N

33. What wear profile shows • Heat treated samples are harder than the non-heat treated so COF as well as wear rate was low in case of heat treated samples. • Heat treated samples has COF below than 0.1 and above for non heat treated samples. • COF is increasing order with respect to time in case of non heat treated samples.

34. Effect on wear due to variation in heat treatment time

35. Friction profiles when specimens were heated at different times Heating time was 30 minutes Heating time was 60 minutes

36. What wear profiles shows • In 30 minutes coating get no enough hard than the 60 minutes. In case of 30 min. Heat treatment COF continuously increases and not in 60 min. heat treatment.

37. Contd...... • Like TCP means tri calcium phosphate which has chemical formulae Ca3(PO4)2 • And second is TTCP called tetracalcium phosphate and its chemical formulae is Ca 4O(PO4)2. And calcium oxide (CaO) also. • These decreases mechanical stability of coating because they easily dissolve in blood plama.

38. SEM image showing pores and unmelted particle

39. Contd.... • Various heat treatment process is done on HA coating to improve its crystallinity, so that there will be minimum dissolution of coating occurred in blood plasma. • means mechanical stability of coating increases when crystallinity increases. • But crystalline phases has low biocompability than the amorphous coating.

40. Conclusions • Wear resistance rate was increased when coated specimen was heat treated. Wear resistance was high at lower loads. And with increasing the heating time wear resistance was incresed. • Porosity was decreased and surface roughness was increased with reinforcement as compared to pure HA coating. However Increment in roughness is very less (slight). Both porosity and surface roughness were increased when coated samples were heat treated. • Crystallinity of the reinforced coating was low as compare to pure HA coating. More phases were formed due to chemical reaction between the HA and reinforced (Al2O3-TiO2) particles of the coating. Crystallinity of coating was increased when heat treatment was done. • Improvement was found in Microhardness with the reinforcement as well as heat treatment of the coating. • Tensile strength of the coating was increased when reinforced with Al2O3-TiO2. Reinforced particles formed stronger chemical bonds with metal substrate.

41. Refrences • Gurbhinder Singh, Surendra Singh, Satya Prakash, “Surface characterization of plasma sprayed pure and reinforced hydroxyapatite coating on Ti6Al4V alloy” Surface & Coatings Technology 205, 4814–4820, 2011 • Yunzhi yang, Kyo-Han Kim, Joo L Ong, “A review on calcium phosphate coatings using sputtering process, Biomaterials 26, pp327-337, 2005 • FAN Xin, CHEN Jian, ZOU Jian-peng, WAN Qian, ZHOU Zhong-cheng, RUAN Jiam-ming, “Bone-like apatite formation on HA/ 316L SS composite furnace in simulated body fluid” Trans. Nonferrous Met. Soc. China 19, 347-352, 2009 • T. Kokubo, H. Kushitani, S. Sakka, T. Kitsugi and T. Yamamuro, “Solutions able to reproduce in vivo surface-structure changes in bioactive glass-ceramic A-W”, J .Bio med Mater Res, 2 4 ,721-734, 1990 • L.-G. Yu , K.A. Khor, H. Li, P. Cheang, “Effect of spark plasma sintering on the microstructure and in vitro behavior of plasma sprayed HA coatings”, Biomaterials 24, 2695-2705, 2003 • M.Gaona, R.S. Limba, B.R. marple, “Nano structured Titania/hydroxyapatite composite coatings deposited by HVOF”, Materials Science and Engineering A, 458, 141-149, 2007

42. References contd... • Chan-Hee Park, Min Young Jung et al, “Characterization and bio-stability of HA/Ti6Al4V ACL anchor prepared by simple heat treatment “ Ceramics International, 38, 5385-5391, 2012 • W. Gu, K.A. Khor, P. Cheang, “In vitro studies of plasma sprayed HA/Ti-6Al-4V composite coating in simulated body fluid” Biomaterials ,24, 1603-1611, 2003 • Daqing Wei, Yu Zhou, “Characteristic and biocompatibility of the TiO2- based coating containing amorphous calcium phosphate before and after heat treatment, Applied surface science, 255, pp 6232-6239, 2009 • S.A. bender, J.D. Bumgardner, M.D. Roach, K. Bessho, J.L. Ong, “Effect of protein on the dissolution of HA coating” Biomaterials 21, 299-305, 2000 • Despina D Deligianni et al., “Effect of surface roughness of hydroxyapatie on human bone marrow cell” Biomaterials Volume 22, issue 1, pages 87-96, 2000