Sulphide inclusion effects on tool-wear in high productivity milling of tool steels

Resulphurised and non-resulphurised tool steels have been compared in high productivity milling processes. Experimental results have shown that the machinability of tool steels, in terms of tool-life, is increased with sulphide inclusions. This increase may seem to depend on the cutting speed, probably due to the existence of an adherent layer of sulphides (MnS) frequently observed in turning. In a follow-up to the previous studies, where it has been shown that at high cutting speeds, the action of sulphur disappears, indicating the importance of the range of cutting parameters, in this paper, a new method involving the use of tool-work material pair to determine the best cutting parameters is presented. The results have have highlighted that Taylor's test-wear law is not suitable to determine the influence of milling parameters on tool-life. A half fractional experimental design method has been used to determine the tool-wear rate and to discuss the effect of each influencing factor including the interactions among these factors. Scanning electron microscope (SEM) techniques have been utilised to study the influence of sulphide inclusions on the tool rake face during progressive tool-wear.