Effect of N₂ and CH₄ gas flow rates on plasma nitrocarburized commercially pure titanium surface hardness

When used as a friction-prone component, commercially pure titanium must be hardened. Plasma nitrocarburizing can increase the hardness of commercially pure titanium. N₂ and CH₄ gases are used as nitrogen and carbon ion sources in plasma nitrocarburizing. The objective of this work is to investigate how the ratio of N₂ to CH₄ gas flow rates affects the thickness and hardness of the thin layer created. At a pressure of 1.6 mbar and a temperature of 450 oC, plasma nitrocarburizing was carried out for 4 hours with different gas flow rate ratios of 1:1, 1:2, 1:3, and 1:4. To analyze the microstructure and surface composition of the material, a metallographic test was performed using a ZEISS EVO Scanning Electron Microscope-Energy Dispersive Spectrometry. To determine the compounds formed, a composition test was conducted using X-ray Diffraction (XRD) with the brand Pw3040 60 X Pert Pro Mpd Diffractometer. The Matsuzawa MMT-X7 Micro Vickers Hardness tester was used to measure surface hardness. Hardness testing on commercially pure titanium nitrocarburized plasma with variations in gas flow rate ratios of 1:1, 1:2, 1:3, and 1:4 resulted in hardness of 312.68 VHN, 134.96 VHN, 111.56 VHN, 109.3 VHN, respectively. The metallographic test by using Scanning Electron Microscope results showed the formation of a thin layer. The thicknesses were 1.88 µm, 1.69 µm, 1.65 µm, and 1.44 µm. This thin layer was confirmed by a composition test formed from TiN and TiC compounds. The plasma nitrocarburizing technique increased the hardness of commercially pure titanium, according to the test results, however, when the flow rate of CH₄ was increased by a ratio of 1:2, 1:3, and 1:4, there was a decrease in hardness compared to a ratio of 1:1. Plasma nitrocarburized commercially pure titanium has the potential to be used in the medical field as a material for hip joint arthroplasty.