Experimental and empirical model analysis of microsurface texturing on 316 L press-fit joints fabricated by selective laser melting

In this study, selective laser melting (SLM) was investigated for the manufacturing of 316L stainless steel press-fit joints. The accuracy of selective laser melting technique in fabrication of texture profile in shape, pitch and height of microsurface texturing was examined. The resulting insertion and removal forces achieved from the produced textured pins for cold-formed high-end fixation applications were studied. The experimental results showed that the shape, pitch and height of the texture, as well as the resultant bonding strength of the joints, can be effectively set via control of the SLM processing parameters. While trapezoidal and triangular shapes of the texture lead to stronger bonding compared with oval-shaped texture profiles, the texture height was found to have a predominant effect on bond strength. To a much lower extent, larger pitch distances also resulted in higher bond strengths. A combination of abrasive and adhesive wear mechanisms was detected via examination of the inner surface of the hub into which the press fit was inserted. Along with a process map of design of the microsurface texture geometry of metal interference fit joints, this paper also presents the underlying mechanics for their bonding. The SLM process is shown to present a useful one-step method for the manufacturing of knurl metallic interference fit pins of customisable and definable texture and ensuing bond strength.