Electrical discharge machining has emerged as one of the most accepted non-traditional machining methods that have the capability of attaining complex shapes and better feature size in difficult-to-machine materials. In this article, an advanced review of conventional electrical discharge machining and micro–electrical discharge machining of difficult-to-machine materials, such as nickel and its alloys, titanium alloys, stainless steel (SUS 304) and advanced ceramics, has been presented. The review begins with an introduction to the conventional electrical discharge machining and micro–electrical discharge machining processes, followed by classifications and a brief discussion on different aspects of micro-manufacturing methods. The current research trends and developments, research gaps and challenges of the conventional electrical discharge machining and micro–electrical discharge machining of nickel and its alloys, titanium alloys (Ti6Al4V), stainless steel and advanced ceramics are also discussed in depth. A brief note on future research trends, based on the available literature, has been included in the last section.

In this work, a systematic study and optimization on direct metal laser sintering (DMLS) of a cBN reinforced Ti6Al4V metal matrix composite (MMC) has been carried out using the response surface methodology (RSM). Variable process parameters such as volume % of cBN (5–15%), laser power (50–60 W), scanning speed (3500–4500 mm/min), and constant parameters such as laser spot diameter (0.2 mm), hatching gap (0.2 mm), and layer thickness (0.4) were considered for the experiments. The RSM was employed to establish a regression equation to predict different output parameters of the sintered samples such as the wear rate, relative density, and microhardness. Based on the developed model, the influence of process parameters on the wear rate, density, and microhardness were accomplished with optimized results. Hence, the result, thus, obtained showed the maximum hardness and density of 519 HV_0.2 and 4.23 g/cm³, respectively, and the minimum wear of 26.49 µm in a testing time duration of 10 minutes. X-Ray Diffraction (XRD) analysis of the fabricated MMC confirms the presence of different phases such as cBN, AlN, TiN, TiB₂, and TiO₂ as a consequence of a series of chemical reactions among cBN and different elements of Ti6Al4V in an argon atmosphere.