Investigations on the properties of composite coatings electro co-deposited on AZ80 Mg alloy using triangular waveform pulse current

Abstract

In this research, boron carbide (B4C) and titanium carbide (TiC) nanoparticles were deposited along with Nickel on AZ80 magnesium alloy substrates. Triangular waveform pulse current was used for depositing the coatings on the substrate. The objective of this research is to investigate the microstructural evolution of the coatings in response to the current density, duty cycle and the concentration of reinforcements in the bath. The influence of process parameters were also assessed in terms of the microhardness and specific wear rate. To enhance the surface properties of AZ80 magnesium alloy, a three component layer was successfully applied via electro co-deposition technique for the first time. The magnesium alloy substrates were cleaned and pretreated as per ASTM B480−88. The pretreated samples were coated at three levels of current density viz. 1.5 A/dm2, 2 A/dm2 and 2.5 A/dm2, and the duty cycle was varied between 30%, 40% and 50%. The concentrations of reinforcements in the bath were kept at 0 g/L, 0.5 g/L and 1 g/L. The samples were coated according to Taguchi L9 orthogonal array with two replications. The microstructural studies conducted using scanning electron microscope (SEM) revealed the defects, grain refinement and homogeneous distribution of reinforcements in the Ni matrix. The deposition and orientation of reinforcements in preferred planes were investigated with XRD. Vickers microhardness tests conducted as per ASTM E384-17 revealed that the sample coated with 2.5 A/dm2current density, 30 % duty cycle, 1 g/L B4C and 0.5 g/L TiC produced the coatings with the highest hardness of 412.56 Hv. The results of the pin on disc wear tests conducted according to ASTM G99 were in agreement with the hardness results and the corresponding microstructure. The sample with the maximum microhardness exhibited the minimum specific wear rate of 2.1 E-08 mm3/Nm. The ability of triangular pulse current waveform to deposit hybrid composite coatings on AZ80 magnesium alloy and enhance its surface properties has been confirmed by the results of this research.

Harnessing friction stir back extrusion process to fabricate microtubes from as-cast Mg–4Zn–0.7Zr-1.6RE magnesium alloy

“…Significant factors that affect the quality of the magnesium tubes could be obtained using statistical approaches by undertaking a substantially lesser number of experiments than conventional methods. Despite the fact that the Taguchi technique has been utilized to optimize numerous manufacturing processes in the literature [12][13][14][15][16][17][18], the FSBE parametric optimization to produce Mg alloy-based microtubes is still unfounded. Therefore, this study investigated the use of the L9 orthogonal Taguchi matrix to understand the influence of each parameter (i.e., tool feed rate, rotation rate, and external billet preheating time) for optimum microhardness and corrosion degradation resistance of ZE41 magnesium alloy microtubes.…”