Surface modification of investment cast-316L implants: microstructure effects

Area of Science:

• Biomaterials Engineering
• Materials Science
• Orthopedic Implants

Background:

• 316L stainless steel is a common material for orthopedic implants like femur stems.
• Surface modification is crucial for enhancing the biocompatibility and osseointegration of metallic implants.
• Hydroxyapatite (HAP) coatings promote bone growth and implant fixation.

Purpose of the Study:

• To investigate the effect of different surface treatments on hydroxyapatite (HAP) layer formation on 316L stainless steel femur stems.
• To compare the efficacy of mechanical polishing, thermal oxidation, and alkaline solution immersion in promoting HAP precipitation.
• To analyze the influence of the substrate's microstructure on HAP layer characteristics.

Main Methods:

• Fabrication of 316L stainless steel artificial femur stems using investment casting and vacuum induction melting.
• Application of surface treatments: mechanical polishing, thermal oxidation, and alkaline solution immersion.
• Characterization of HAP layer formation and microstructure using appropriate analytical techniques.

Main Results:

• Thermal oxidation resulted in a thicker HAP layer compared to mechanical polishing.
• Alkaline treatment significantly enhanced HAP precipitation on the steel surface.
• HAP precipitation varied across different microstructural phases, with austenite favoring smoother and more homogeneous layers.
• HAP growth was observed to be preferentially promoted on the austenite phase over the ferrite phase.

Conclusions:

• Surface treatments play a vital role in tailoring HAP coating properties on 316L stainless steel implants.
• Thermal oxidation and alkaline treatments are effective methods for enhancing HAP layer formation.
• The substrate's microstructure, specifically the austenite phase, influences HAP layer homogeneity and growth, suggesting potential for targeted surface engineering.