Case-hardening steels (EN36, 16MnCr5, and AISI 4140) are used in applications demanding good surface properties such as precision gears, shafts, and cam rollers. This study explores the formation of microcoatings to improve the surface characteristics of these steels using carbonitriding, which combines the merits of carburizing and nitriding to offer surfaces with enhanced hardness and wear resistance. Taguchi’s L18 orthogonal array is used for conducting the carbonitriding trials with replications. The effects of various carbonitriding parameters like carbonitriding time, temperature, and flow rate of ammonia are studied on the treated surface characteristics (Vickers microhardness, diffusion depth, and wear loss). A novel integrated approach of principal component-based grey incidence (PGI) that combines the merits of both principal component analysis and grey incidence theory is effectively used to select the optimal carbonitriding inputs (material substrate AISI 4140, carbonitriding temperature −835°C, carbonitriding time-40 min, and flow rate of ammonia 0.4 lit/min). Microscopic images related to diffusion depths are also analyzed. This study offers the necessary guiding principles for obtaining the desired surface coating on EN36, 16MnCr5, and AISI 4140 steels.

In this study Finite Element Analysis (FEA) model is developed to understand the effect of low velocity impact on hybrid (Carbon/Glass/Epoxy) composite pipes which were wound using the filament winding technique in two different diameters. The results were compared with the existing experimental results and further validated FEA model was used to understand the effect of varying thickness and change of helix angle in the impact using ABAQUS tool. In this FEA design, composite pipe was modelled with the orientation of (CG90/CG60) for varying thicknesses (2.67mm, 4mm, 5.3mm and 6mm) and helix angles with variations as 15°, 30°, 45°, 60°, 75°, and 90° respectively. Hybrid pipe model was subjected to three different levels of impact energy namely as 20 J, 25 J and 30 J. Effect of impact studied in terms of force, deflection and energy absorbed by the specimen. The possibility of increasing in the energy absorption through increasing thickness and withstanding high impact forces and impact resistance decreasing with increase in the helix angle of orientation namely, as 15°, 30°, 45°, 60°, 75°, and 90° respectively was seen.

Gas carburizing is an effective surface treatment process for improving the hardness and wear resistance of different class of steels. The study reports an application of grey-incidence based Taguchi (GIBT) method in gas carburizing of case-hardening steels like AISI 4140, EN36, and 16MnCr5 which are widely employed in precision levers, transmission shafts, and pinions. Carburizing trials are performed using Taguchi’s L9 orthogonal array by varying the design parameters like carburizing temperature, soaking time, and tempering temperature. Surface hardness (SH), diffusion depth (DD), and wear loss (WL) are studied as process responses at the completion of various carburizing trials with replications. Optimal design variables are identified using grey incidence grade as a performance index in the GIBT method. The contribution of individual parameters is also studied using the analysis of variance (ANOVA). Microscopic examination and SEM images of the treated surface are also studied after validating the method of GIBT.