Friction Stir Processing of Stainless Steel for Ascertaining Its Superlative Performance in Bioimplant Applications

Abstract

Substrate-cell interactions for a bioimplant are driven by substrate's surface characteristics. In addition, the performance of an implant and resistance to degradation are primarily governed by its surface properties. A bioimplant typically degrades by wear and corrosion in the physiological environment, resulting in metallosis. Surface engineering strategies for limiting degradation of implants and enhancing their performance may reduce or eliminate the need for implant removal surgeries and the associated cost. In the current study, we tailored the surface properties of stainless steel using submerged friction stir processing (FSP), a severe plastic deformation technique. FSP resulted in significant microstructural refinement from 22 μm grain size for the as-received alloy to 0.8 μm grain size for the processed sample with increase in hardness by nearly 1.5 times. The wear and corrosion behavior of the processed alloy was evaluated in simulated body fluid. The processed sample demonstrated remarkable improvement in both wear and corrosion resistance, which is explained by surface strengthening and formation of a highly stable passive layer. The methylthiazol tetrazolium assay demonstrated that the processed sample is better in supporting cell attachment, proliferation with minimal toxicity, and hemolysis. The athrombogenic characteristic of the as-received and processed samples was evaluated by fibrinogen adsorption and platelet adhesion via the enzyme-linked immunosorbent assay and lactate dehydrogenase assay, respectively. The processed sample showed less platelet and fibrinogen adhesion compared with the as-received alloy, signifying its high thromboresistance. The current study suggests friction stir processing to be a versatile toolbox for enhancing the performance and reliability of currently used bioimplant materials.

Excellent Corrosion Resistance of Dual‐Phase Bimodal Stainless Steel

“…The bimodal specimen had fine grains embedded in the matrix of coarse grains (≈10 μm) with an average grain size of nearly 3.5 μm. In contrast, UFG had fine equiaxed grain structure with an average grain size of nearly 0.9 μm compared to 22 μm for the as‐received steel . The TEM image of the bimodal specimen showed fine grains of the order of 200–400 nm (Figure b).…”

Enhanced Biocorrosion Resistance and Cellular Response of a Dual-Phase High Entropy Alloy through Reduced Elemental Heterogeneity

“…The schematic representation of the SFP process is shown in Figure . It is an adaptation of a well-known FSP technique wherein the tool is rotated at a localized position of the workpiece instead of having a transverse motion. , The snapshot of the actual SFP on the HEA specimen is also shown in the figure. SFP resulted in the evolution of a significantly different microstructure in MoNbTaTiZr HEA compared to FSP as discussed below.…”

In situ titanium phosphate formation on a titanium implant as ultrahigh bonding with nano-hydroxyapatite coating for rapid osseointegration

“…However, for the TiP-Ca coating samples, the morphology of the wear area becomes compact due to the load. 40,43 Elemental analysis by EDS shows that the main elements are still uniformly distributed on the implant surface, and no obvious coating peeling occurs. An ultrasonic cleaner was used to check the stability of the coating.…”

“…The friction wear testing was carried out under 5 N normal load. 43,44 The friction coefficient curves of different samples under the same normal load are shown in Fig. 2f.…”