**2. Experimental procedure**

#### **2.1 Preparation of substrates and feedstock powder coating processes**

The alloy samples of SS 316L, CoCrMo & Ti6Al4V were cut to form an approximate disc having 40x5 mm diameter size. The surface of coated samples is prepared using alumina (Al2O3) of size 65–90 μm in a grit blaster within a blasting pressure range of 0.50 MPa for better adhesion of coating powders. After grit blasting the samples were air blasted to clean the surface from alumina contamination before final coating. **Table 1** shows the chemical composition of HA-CNT powder for coating substrate materials. Commercially available HA powder was used for coating deposition which was procured from Xi'an Prius Biological Engineering Co., Ltd. XS province, China, and MWCNT procured from Adnano Technologies Pvt. Ltd., Karnataka, India was used as reinforcing material. Reinforcing material was mixed in pure hydroxyapatite Powder in 10% and 5% by weight using laboratory ball mill up to 10 hours for uniform mixing of reinforced HA coating at Plasma Spray Coats, Bangalore, India. Particle size, composition (wt.%) with powder designation are shown in **Table 1**.

Morphological studies of bare hydroxyapatite powder with carbon nanotube reinforcement on coated alloy substrates have been carried out using scanning electron micrographs. These powders were also characterized by the XRD technique


**Table 1.**

*Chemical composition and other details of HA-CNT coating powder.*

using the Xta-LABminiTM Benchtop X-ray Diffraction/Crystallography system from Rigaku Americas Corporation in the angle range of 20°– 90°. **Figures 1** and **2** depict the micrographs and EDX analysis of (10 wt% and 5 wt%) reinforced HA-C coating. SEM micrograph shows that reinforced material has crushed angular and ball shape.
