**2.2 EN Co-deposition on cutting tools**

The end mill cutting tool using carbide and high-speed steel (HSS) with a dimension of 6 mm was used as a substrate of Ni-CBN coating as shown in **Figure 3**. Before EN co-deposition process done on both cutting tools, chemical etching and mechanical blasting were used to modify the surface of the substrate sample to ensure better substrate-coating bonding.

Sensitising the HSS and Carbide cutting tool substrates is needed to activate the surfaces. Because of this, all non-proprietary solutions were produced using AR-grade chemicals and high purity deionised water. The EN co-deposition of Ni-CBN was conducted within 3 hours of the pre-treatment process, as shown in **Table 4**, to reduce the impacts of chemical degradation [46]. The EN chemicals produced a bright nickel deposit with a mid-phosphorous content between 6 to 9 wt.%. The optimum temperature for electroless nickel solution is at 89°C and was heated using a Jenway hotplate.
