Effect of Nitrided and Nitrocarburised Austenite on Pitting and Crevice Corrosion Resistance of 316 LVM Steel Implants

Abstract

Harmful lesions occur in the body around multielement stabilisers made of AISI 316 LVM (Low Vacuum Melted) steel, caused by products of pitting, fretting or crevice corrosion. Preventing the effect is possible by modifying the surface of the steel implants. Therefore, the goal of the paper is the comparison of the mechanical and physiochemical properties of plates for treating deformations of the anterior chest wall made of AISI 316 LVM steel, subjected to diffusion and sterilisation processes and exposed to Ringer’s solution. The surface of the implants was subjected to electrochemical polishing, chemical passivation and, in order to modify their properties, nitrocarburised and nitrided diffusion layers were created on selected stabilisers under glow discharge conditions with the use of an active screen at a temperature of 420 °C, over 60 min. The conducted studies involved the examination of the microstructure of the formed layers, surface roughness testing, analysis of contact angles and surface free energy, examination of resistance to pitting and crevice corrosion and examination of nanohardness. On the basis of the results of the conducted studies, it was established that the most advantageous set of properties after sterilisation and exposure to Ringer’s solution was displayed by implants with a formed diffusion nitrocarburised layer.

Analysis of the New Forming Process of Medical Screws with a Cylindrical Head of 316 LVM Steel

“…This grade is a modified version 316 with low carbon, high nickel and molybdenum content [ 2 , 3 ]. The improvement of the chemical composition is aimed at maximising the material’s resistance to corrosion by obtaining a ferrite-free metallographic structure [ 4 ]. In order to ensure the purity and homogeneity of 316 LVM steel, a double vacuum induction melting + vacuum arc remelting process is generally used.…”

Enhancing the Corrosion Resistance of Austenitic Steel Using Active Screen Plasma Nitriding and Nitrocarburising

“…Superaustenitic steels produce values of resistance to pitting corrosion that clearly exceed those of commonly used austenitic steels, which are not stabilised by nitrogen [ 5 ]. Similar or even better corrosion resistance results can be obtained by the application of low-temperature nitriding (<450 °C) [ 7 , 8 , 9 , 10 , 11 , 12 ], carburising (<500 °C) [ 13 , 14 , 15 ] or nitrocarburising (<450 °C) [ 16 , 17 , 18 , 19 ] of austenitic steels that do not contain significant additions of nitrogen in their structure, such as, for example, AISI 304L, AISI 316L or AISI 321 steel. In these processes, the face centred cubic structure (fcc), which is present in the steel’s surface layer, shows a certain degree of deformability, which is dependent on the concentration of nitrogen and/or carbon [ 17 , 20 ].…”

“…Furthermore, it was found that an expanded nitrocarbon austenite layer, which was thinner and had lower surface roughness, featured a higher corrosion resistance value. In another study, Kajzer et al [ 18 ] examined implants for treating deformations of the anterior chest wall made of AISI 316 LVM (Low Carbon, Vacuum Melt) steel, which were subjected to active screen nitriding, nitrocarburising (T = 420 °C, t = 60 min), sterilisation and exposed to Ringer’s solution at 37 °C. Such steel, compared to AISI 316L, exhibits better resistance to localised corrosion due to its slightly modified chemical composition and manufacturing process (vacuum melting).…”

Repair of Large-Scale Rib Defects Based on Steel-Reinforced Concrete-Designed Biomimetic 3D-Printed Scaffolds with Bone-Mineralized Microenvironments

“…The soft tissue could be easily reconstructed by covering with the surrounding muscles or transmyocutaneous flaps . However, the bony structure is difficult to reconstruct, especially for large-scale rib defects, owing to the lack of satisfactory bone repair materials. , At present, artificial materials such as steel plates or ceramics are mainly used in clinics. ,, However, clinical requirements have not yet been fully satisfied by artificial materials because of the lack of biological activity and physiological functions and the possibility of complications such as foreign body rejection and infection. , …”

“…6,7 At present, artificial materials such as steel plates or ceramics are mainly used in clinics. 6,8,9 However, clinical requirements have not yet been fully satisfied by artificial materials because of the lack of biological activity and physiological functions and the possibility of complications such as foreign body rejection and infection. 10,11 Currently, tissue engineering based on seed cells and biodegradable scaffolds is considered a promising strategy for physiological bone regeneration and functional reconstruction.…”