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Response surface methodology (RSM), Tungsten carbide cobalt composite (WCCo). A B S T R A C TIn this two-part research, a unified approach is presented to model and optimize the electro-discharge machining (EDM) parameters on WC/6%Co using response surface methodology (RSM) and desirability function (DF) concept. In the first part, four controllable parameters, viz., discharge current (A), pulse on-time (B), duty cycle (C), and average gap voltage (D) have been selected as the input variables to evaluate the process performance in terms of material removal rate (MRR), tool wear rate (TWR), and arithmetic mean surface roughness (Ra) as the performance characteristics. The modeling phase begins applying face-centered central (FCC) composite design to plan and analyze the experiments in accordance with the RSM. For every response, the significant forms of influential parameters were properly identified conducting a comprehensive analysis of variance (ANOVA) at 1, 5, and 7% level of significance. It has been revealed that all the direct effects of input parameters are extremely momentous affecting both the MRR and TWR. Moreover, the pure quadratic effect of duty cycle (C 2 ), the reciprocal effects of discharge current with pulse on-time (A×B), duty cycle (A×C), and gap voltage (A×D), as well as the interaction amongst the pulse on-time with duty cycle (B×C) were also reached to be important terms affecting the MRR. The TWR measure behaves the same way, however, it exhibits a more nonlinear mathematical form containing the second order effect of discharge current (A 2 ) as an additional important term. On the other hand, for the Ra, the only significant parameters are the main effects of the first two inputs (A and B) plus the interactions of current with pulse on-time (A×B) and with gap voltage (A×D). The results indicate that the suitably proposed step-by-step implemented approach can substantially elucidate the highly multifaceted behavior of the chosen grade WC-Co under different EDM conditions providing a reliable platform to both navigating the operational region and seeking for optimal working circumstances confidently.

Abstract:Titanium nitride thin films deposited by reactive dc magnetron sputtering under various substrate bias voltages have been investigated by X-ray diffraction. TiN thin films exhibits lattice parameter anisotropy for all bias voltages. Preferential entrapment of argon atoms in TiN lattice has been identified as the major cause of lattice parameter anisotropy. Bombardment of argon ions during film growth has produced stacking faults on {111} planes of TiN crystal. Stacking fault probability increases with increasing substrate bias voltages. X-ray diffraction line profile analysis indicates strain anisotropy in TiN thin films. Diffraction stress analysis by d-sin 2 ψ method reveals pronounced curvature in the plot of interplanar spacing (d) (or corresponding lattice parameter (a)) versus sin 2 ψ. Direction dependent elastic grain interaction has been considered as possible source of the observed anisotropic line broadening. IntroductionTitanium nitride (TiN) thin films deposited by reactive magnetron sputtering is widely used for improving the hardness and wear resistance of materials surfaces [1]. Such functional properties critically depend on the microstructure of TiN thin films. It is well known that ion bombardment during thin film deposition can change the microstructure of such hard coating [2][3][4]. During the films deposition, the substrate is negatively biased (with respect to deposition chamber) so that the positively charged ions of the sputtering gas such as argon can be accelerated towards the substrate during the film growth. Negative bias voltage of the substrate can be varied in order to change the energy of the bombarding ions which is the key to change the film microstructure. In the present work, microstructure of TiN thin films deposited at various substrate bias voltages has been studied by X-ray diffraction. Intrinsic/growth stresses and crystallographic textures in TiN films have been studied as a function of substrate bias voltages (i.e. energies of the bombarding ions). Specimen preparation and characterizationPolycrystalline titanium nitride thin films (thickness ~ 2µm for all films) were deposited on silicon ({100} Si) substrate by planer reactive dc magnetron (magnetron power ~ 270W) sputtering under various substrate bias voltages (0kV to -5kV) using a high voltage pulsed DC power supply. The sputter target was 99.99% pure titanium and argon gas of high purity (99.99%) was used as the sputtering gas for the magnetron targets. For the reactive deposition of titanium nitride, the reactive gas nitrogen was introduced. Operating pressure of the sputtering chamber was 3x10