Influence of Nano Al2O3 Particles on the Adhesion, Hardness and Wear Resistance of Electroless NiP Coatings

Abstract

Abstract-In this present study electroless NiP coatings and NiP-Al 2 O 3 coatings had been deposited on a mild steel substrate. The surface morphology of both the coatings had studied using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction technique. Adhesion, hardness and wear behavior were investigated and compared for NiP and NiP-Al 2 O 3 coatings. Optical micrograph images were used for the evaluation of adhesion of coatings which found sufficient and acceptable according to VDI 3198 standard. Hardness of the coating had been evaluated based on depth sensing techniques and substrate effect had avoided by maintaining depth to coating thickness ratio less than 0.1. Due to co-deposition of Al 2 O 3 particles the hardness of NiP coatings increased by 20.5% (7.8 GPa to 9.4 GPa). Dry sliding wear tests were conducted on PLINT TE66 micro scale tester against steel ball of hardness 800 HV. Wear resistance of NiP coatings increased with increase in sliding distance. The co-deposition of Al 2 O 3 particles in NiP matrix arrest the deformation during sliding of steel ball and thus wear resistance of NiP-Al 2 O 3 coatings is superior to NiP coatings. Wear crater morphology were studied using SEM and EDS. Adhesive wear mechanics was observed in NiP coatings and combination of adhesive and abrasive wear mechanism were found in NiP-Al 2 O 3 coatings.

Microstructural, Surface Topology and Nanomechanical Characterization of Electrodeposited Ni-P/SiC Nanocomposite Coatings

“…In the case of the elastic modulus as shown in Figure 8(b) the effect of SiC codeposition is higher than heat treatment as Ni/SiC has higher elastic modulus values than both as-plated and heat treated Ni-P. The data that are reported in Figure 8 are in a good agreement with the results of other experimental efforts, since the literature [3,[47][48][49][50][51][52] reports values for the as plated, untreated condition of plain Ni-P coatings for hardness, ranging from 4 to 8 GPa, depending mainly on the P The hardness (H) and the elastic modulus (E) of as-plated Ni-P, Ni-P/SiC, and heat-treated coatings were calculated from the load-displacement curves. Figure 8 demonstrates the calculated mechanical properties, as elastic moduli and hardness, for all of the under study samples.…”

“…The XRD spectra of the non-treated specimens show the characteristic peak of the amorphous Ni-P structure that was also observed in other studies [1][2][3][4][5]42,43]. It has been reported that the amorphisation of Ni due to the high amount of phosphorus is due to the fact that P presence within the lattice and the subsequent strain fields it causes, lead to primary grain growth inhibition that becomes so intensive, so that practically nanocrystallinity and eventually amorphisation is achieved [1][2][3][4][5][6]. However, the overall structure has been totally altered after the application of heat treatment, as it can be seen in Figure 4.…”

“…Narrow intensive peaks in all cases declare the crystallization process taking place during this stage. Phase identification does verify the crystallization process, which is also observed in many other cases [1][2][3][4][5], as crystalline Ni FCC phase is distinguished in all samples along with the presence of the precipitated Ni3P intermetallic phase, which is also a classical outcome of the heat treatment and crystallization process [1][2][3][4][5][6]. XRD did not reveal the presence of SiC phase in the case of heat treated samples as compared to the as-coated samples.…”

“…In the case of the plain coatings (no SiC reinforcement), heat treatment seems to increase the intensity of the surface landscape and, as such, the surface roughness. P incorporation during the plating stage induces amorphisation, as already mentioned [1][2][3][4][5][6]. This amorphisation is reported to be initiated by the severe crystalline grain growth restriction.…”

“…The development of coatings has been recognized early as one of the most promising and effective process towards this direction. The excellent wear and corrosion resistance of the Ni-P (nickel-phosphorous) coatings makes them very good candidates for application where surface is under load and aggressive environment [1][2][3][4]. The two major deposition techniques for Ni-P coating systems are the electroand electroless deposition, with the first to provide high deposition rates and the second to provide coatings of exceptional thickness uniformity, even at the complicated geometrical features [1][2][3][4][5].…”