Partially degradable friction-welded pure iron-stainless steel 316L bone pin

Abstract

This article describes the development of a partially degradable metal bone pin, proposed to minimize the occurrence of bone refracture by avoiding the creation of holes in the bone after pin removal procedure. The pin was made by friction welding and composed of two parts: the degradable part that remains in the bone and the nondegradable part that will be removed as usual. Rods of stainless steel 316L (nondegradable) and pure iron (degradable) were friction welded at the optimum parameters: forging pressure = 33.2 kPa, friction time = 25 s, burn-off length = 15 mm, and heat input = 4.58 J/s. The optimum tensile strength and elongation was registered at 666 MPa and 13%, respectively. A spiral defect formation was identified as the cause for the ductile fracture of the weld joint. A 40-µm wide intermetallic zone was identified along the fusion line having a distinct composition of Cr, Ni, and Mo. The corrosion rate of the pin gradually decreased from the undeformed zone of pure iron to the undeformed zone of stainless steel 316L. All metallurgical zones of the pin showed no toxic effect toward normal human osteoblast cells, confirming the ppb level of released Cr and Ni detected in the cell media were tolerable.

Mechanical and corrosion properties of partially degradable bone screws made of pure iron and stainless steel 316L by friction welding

“…The surface of the rods has a roughness of 0.34±0.05 μm for SS316L and 0.62±0.06 μm for iron, measured by using a 3D digital microscope (Hirox KH-8700, Japan). By referring to our previous work [15], the FW was done on a modified lathe (Knuht DM 1000A -5.7 kW, Germany) using the following parameters: rotation spindle of 1600 rpm, forging pressure of 33.2 kPa, friction time of 25 s and long burn-off of 15 mm. All specimens were cut from the friction welded iron-SS316L rods with specific dimension according to the requirement for the various tests described in the following.…”

“…Implant specimens (9×1.4×0.8 mm 3 ) were cut from the welded metals. The length of the implant includes three critical sections: iron section, iron-SS316L interface and SS316L section, as determined in our previous study [15]. The rats were subjected to a standard surgical procedure (acclimatization, implantation, monitoring, data collection and termination) under the supervision of the Animal Hospital of Bogor Agricultural University.…”

“…After the recent successful clinical trials [13,14], bone screws made of magnesium alloys are now commercially available for clinical use. In our previous work, we demonstrated that among the three classes of biodegradable metals, pure iron was successfully joined with SS316L by using a friction welding (FW) technique [15]. Thanks to the use of an optimum welding parameter, the welded metals possessed a good combination of strength and ductility and a gradual increase of corrosion rate from the stainless steel side to the pure iron side.…”

An In Vitro Corrosion Study of Open Cell Iron Structures with PEG Coating for Bone Replacement Applications

“…These novel kinds of implants can adapt to the needs of the human body in which they are implanted. Their role is to support initially the formation of the healing injured tissues and subsequently to degrade gradually, while the tissue function is repaired [2][3][4][5][6]. The degradable determined by the material, porosity (morphology, size, and distribution of pores), and density of the created foam [61,62].…”

Electroforming as a New Method for Fabricating Degradable Pure Iron Stent

“…The correct integration of these elements is one of the issues of the present study of electroforming processes, as they need an extensive experimental assessment in order to achieve optimized systems. The development of electroformed iron enriches the choice of biodegradable metals available for cardiovascular stent [32] and expectedly useful for other applications such as bone implants [33,34].…”