Parameter Design in Carbonitriding of EN36, 16MnCr5, and AISI 4140 Steels Using Principal Component-Based Grey Incidence (PGI)

Abstract

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.

Study on the Tribological Properties of DIN 16MnCr5 Steel after Duplex Gas-Nitriding and Pack Boriding

“…Conversely, gas-nitriding and pack boriding showed greater wear resistance compared to the quenched and tempered DIN 16MnCr5 steel, resulting in reduced volumetric wear. This behavior aligns with findings in the literature, attributing the wear resistance to hardened surfaces influenced by compound layers and the diffusion nitriding zone [16,18,19] as well as the presence of iron borides and the formation of a solid solution of The results of the volume loss from the pin-on-disc sliding test conducted under dry conditions using loads of 2 N, 4 N, and 6 N with a sliding distance of 100 m on quenched and tempered DIN 16MnCr5 and surface treatments such as gas-nitriding, pack boriding, and duplex gas-nitriding and pack boriding are presented in Figure 15. The results indicate that the quenched and tempered DIN 16MnCr5 steel exhibited the highest volumetric wear.…”

“…Conversely, gas-nitriding and pack boriding showed greater wear resistance compared to the quenched and tempered DIN 16MnCr5 steel, resulting in reduced volumetric wear. This behavior aligns with findings in the literature, attributing the wear resistance to hardened surfaces influenced by compound layers and the diffusion nitriding zone [16,18,19] as well as the presence of iron borides and the formation of a solid solution of boron in iron [23][24][25][26]. In comparison, the surface treated with duplex gas-nitriding and pack boriding displayed the highest wear resistance due to the combined effect of enhanced mechanical properties, including increased hardness and elastic modulus.…”

“…Vivek [17] studied how carbonitriding with propane and ammonia gases affected the mechanical properties and hardness of DIN 16MnCr5. Similarly, Arumparithy et al [18] combined carburizing and nitriding using CO 2 and ammonia to enhance the hardness and wear resistance of DIN 16MnCr5 steel. Caliari et al [19] investigated nitriding on DIN 16MnCr5 steel using ammonia (NH 3 ) (50%), CO 2 , and N 2 for 4 h, resulting in improved mechanical properties and increased hardness.…”

“…After the gas-nitriding treatment of quenched and tempered DIN 16MnCr5 samples, the diffraction patterns were ε-Fe3N (PDF 04-007-3377) (110) at 38.32°, (002) at 41.3°, (111) at 43.75°, (112) at 57.60°, (300) at 69.3°, (113) at 77.01°, and (302) at 83.99°, as well as γ'-Fe4N (PDF 01-071-4924) (111) at 41.14°, (200) at 47.89°, (220) at 70.03°, and (311) at 84.57° as a function of temperature and nitriding potential described by the Lehrer diagram[29]. This indicates that the surface layer is mainly composed of ε-Fe3N and γ'-Fe4N, providing higher hardness and improved wear resistance[14][15][16][17][18][19][20]. The diffraction patterns for the pack boriding treatment of quenched and tempered DIN 16MnCr5 steel samples exhibit peaks corresponding to the main phases formed in the surface layer FeB (PDF 04-007-6176) (200) at 32.56°, (201) at 39.58°, (111) at 41.…”