Taguchi design method of optimization facilitates standard experimental research, lowers cost, conserves energy and time, minimizes waste and ensures optimal outcomes. In this work, Taguchi L9 3 4 orthogonal array, signal-to-noise (S/N) ratio and analysis of variance (ANOVA) statistical procedures were applied to evaluate the influence of sintering parameters/levels on the relative densification and microhardness of Ti-6Al-4V/h -BN binary composite sintered. The S/N ratios revealed that heating rate with delta value of 0.24, followed by temperature with delta value of 0.22 impart the most significant influence on the optimal quality characteristics. One-way ANOVA statistical analyses showed that heating rate imparts the greatest influence on relative densification with 36.25% contribution, followed by temperature with 31.33% contribution, whereas temperature gave the highest contribution of 34.12%, followed by heating rate with 23.31% contribution for microhardness. The optimal parameters/levels for most desirable characteristics were obtained at 1000 °C, 30 MPa, 100 °C min −1 and 10 min. The spark plasma sintered Ti6Al4V-3h-BN composite with the optimized parameters/levels attained nearly full theoretical densification of 99.54% and the sintered composite gave a microhardness value of 716.43 HV which is more than 200% that of the monolithic alloy. The confirmation test revealed that the improvement in relative densification and microhardness at the optimum parameters/levels are 1.55% and 19.2% of the arithmetic means of the initial relative densification and microhardness measurements respectively.

The cold spray coating process involves many process parameters which make the process very complex, and highly dependent and sensitive to small changes in these parameters. This results in a small operational window of the parameters. Consequently, mathematical optimization of the process parameters is key, not only to achieving deposition but also improving the coating quality. This study focuses on the mathematical identification and experimental justification of the optimum process parameters for cold spray coating of titanium alloy with silicon carbide (SiC). The continuity, momentum and the energy equations governing the flow through the low-pressure cold spray nozzle were solved by introducing a constitutive equation to close the system. This was used to calculate the critical velocity for the deposition of SiC. In order to determine the input temperature that yields the calculated velocity, the distribution of velocity, temperature, and pressure in the cold spray nozzle were analyzed, and the exit values were predicted using the meshing tool of Solidworks. Coatings fabricated using the optimized parameters and some non-optimized parameters are compared. The coating of the CFD-optimized parameters yielded lower porosity and higher hardness.

The microstructure, penetration depth and mechanical properties of gas metal arc weldments of AISI 304 stainless steel were investigated within a process window. 9 weldments were produced using Taguchi L9 orthogonal array technique. Well bonded, crack-and pore-free weld joints were obtainable at wire feed rate of 66-96 mm/s, voltage of 19-25 V and welding speed of 5.0-9.6 mm/s. The weld joint hardness (305-395 HV) decreased with increasing the heat energy input. However, weld penetration depth (2.67-4.86 mm) increased as the heat energy input increased. Full weld penetration was achieved at heat energy value of 519 J/mm. The ultimate tensile strength (UTS) first increased with increasing the heat energy input until an optimum value of 765 ± 12 MPa was obtained at 519 J/mm after which there was a decline. The weld penetration of the joints is adjudged to play a significant role on the UTS of the weldments.

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