Effect of abrasive flow machining (AFM) finish of selective laser melting (SLM) internal channels on fatigue performance

Conformal cooling channel technology is becoming a common practice in the design of injection moulds made of maraging steel thanks to additive processes such as selective laser melting (SLM). However, the rough surface created by SLM can have an adverse effect on the fatigue life of the mould because of the rough channel surfaces that induce stress concentrations in the valleys of the roughness. So as to overcome this problem, abrasive flow machining (AFM) has been applied on SLM produced channels. This paper investigates the influence of this superfinishing technique on the surface roughness and on the residual stress state of channels. It is shown that AFM is capable of improving the surface roughness and inducing compressive residual stresses. Then, this work proposes an original testing method to characterise the fatigue resistance of internal channels, that reveal that AFM is able to improve significantly the fatigue strength of channels and to recover the fatigue strength commonly obtained with electrical discharge machining (EDM).