EFFECT OF ELECTRON BEAM PROCESSING PARAMETERS ON THE SURFACE ROUGHNESS OF TITANIUM SAMPLES: PART II

Titanium and its alloys are widely recognized as preferred materials in biomedical engineering, especially for orthopedic implants such as artificial hip joints, owing to their outstanding biocompatibility, corrosion resistance, low density, and favorable mechanical characteristics. Among them, the Ti-6Al-4V alloy is particularly prominent for hip implant applications because of its superior strength-to-weight ratio, high resistance to corrosion in physiological environments, and strong capacity to facilitate osseointegration. In addition, titanium possesses a comparatively low elastic modulus relative to other metallic biomaterials, which helps to mitigate stress shielding and ensures more effective load transfer to the surrounding bone. Although titanium offers many beneficial properties, the clinical performance of titanium implants is strongly influenced by the material’s surface characteristics. Parameters such as surface roughness, chemistry, and topography are widely recognized as key determinants of biological interactions at the bone–implant interface. Among these, surface roughness is particularly significant, as it regulates cellular responses, impacting adhesion, proliferation, differentiation, and ultimately the integration of bone tissue. A substantial body of research indicates that moderately rough surfaces (with an average roughness, Ra, of 1–2 μm) support osteoblast differentiation and improve bone-to-implant contact when compared to both smoother and excessively rough surfaces. In contrast, overly smooth surfaces may promote fibrous tissue encapsulation, whereas excessively rough ones can provoke inflammatory reactions and accelerated wear. Additionally, surface roughness influences the mechanical interlocking between the implant and bone, a key factor for achieving primary stability and reducing micromotion during the initial healing phase. Inadequate primary stability can delay or prevent osseointegration, ultimately jeopardizing the long-term success of the implant. Recognizing these critical implications, considerable efforts have been devoted to the development of surface modification techniques to optimize implant surface properties. Conventional approaches, including grit blasting, acid etching, anodization, and plasma spraying, have been widely employed to enhance the surface characteristics of titanium. In recent years, electron beam processing has emerged as a promising technique, offering precise control over surface morphology, microstructure, and roughness, while minimizing the risk of chemical contamination. A comprehensive understanding of the relationship between electron beam processing parameters—particularly the number of passes—and surface roughness is fundamental to the design of implants with superior biological performance. In this context, the present study provides a systematic evaluation of the effect of pass number on the surface roughness of titanium specimens processed under a fixed beam current of 1.0 mA, offering critical insights into the refinement of surface modification strategies aimed at enhancing clinical outcomes in hip joint arthroplasty. In summary, the experimental setup maintained a constant electron beam current of 1.0 mA while systematically varying the number of passes (2, 4, 8, and 16) to investigate its influence on the surface roughness of titanium samples.