Development of Fe-13.8Cr-8.9Mn alloy for steel biomaterials

Abstract

Traumatic, osteoarthritic, tumoral, and congenital bone issues impact human lives and health. The next generation of bone implants is made from biodegradable materials, including Fe-based materials with superior mechanical properties and high biocompatibility. However, efforts to inhibit the risk of inflammation and bacterial infection due to the biological response and corrosion properties of metals are a significant challenge. This study aims to develop biomaterials based on Fe-Cr-Mn alloys to obtain superior physical and mechanical properties through plasma nitriding. Each sample was plasma-nitridated in a vacuum chamber at various temperatures of 250–450 °C for 3 hours at a pressure of 1.8 kPa. Several main tests were performed to investigate the effects of plasma nitriding, such as the chemical compositions of raw material, surface nitrogen contents, phase changes, thickness, hardness, and corrosion. Those parameters were then used to evaluate plasma nitriding's effectiveness, including observing the change in phenomena at each temperature treatment. The results indicated that forming the S phase on the surface of Fe-13.8Cr-8.9Mn alloy is a saturated solution of nitrogen in ɣ-Fe, where the nitrogen content on the surface increases with increasing nitriding temperature. The layer's surface hardness is uniform across its whole thickness, which reduces as the grade of raw material passes through the nitride layer. The highest hardness at a nitriding temperature of 450 °C reached 625.3 VHN. The findings showed that the corrosion rate decreased significantly, reaching the lowest value, 0.0018 mm/year, at a plasma nitriding temperature of 450 °C. Plasma nitriding could enhance the physical and mechanical properties of Fe-Cr-Mn alloy