Comparison of the life-span of NbC-Co and WC-Co inserts during different machining operations on 100Cr6 (SAE 52100) bearing steel

Carbide products have in recent years become indispensable for the machining of steels and indeed carbide tools generally show longer tool life and produce higher dimensional accuracy. In the majority of cases, carbide tools will leave a better finish on the part and allow faster machining. Carbide tools can also withstand higher temperatures than high speed steel tools. Nevertheless carbide tools are more expensive per unit than other typical tool materials and tend to be brittle, making them more susceptible to chipping and breaking. The aim of the study presented in this paper is to highlight the potential of niobium carbide cutting tool inserts for machining and to compare their performance to commercially available tungsten carbide inserts. In this work, a comparison between a conventional WC-Co insert (with 6%Co) and NbC-Co inserts (with 8% and 12%Co) was carried out under hard machining conditions on specimens made of 100Cr6 bearing steel grade (SAE 52100). The objective was to determine if NbC-Co type inserts were a good candidate as an alternative material to WC-Co. The results showed the significantly higher wear resistance of the NbC-Co inserts but a lack of toughness compared to the WC-Co insert. Further comparisons were made between a WC-Co insert and an NbC-Fe3Al (with 12%Fe3Al) insert in semi-finishing operations. Here again, the higher wear resistance of the NbC-12Fe3Al insert was evident with no collapse after about one hour of machining. The crater wear was three times larger for the WC-Co inserts compared with the NbC inserts while the flank wear was the same for each type of insert. All these results are promising regarding the high abrasive resistance of the NbC inserts but improvements are still needed to increase the toughness for hard machining operations and work is currently in progress to attain this toughness enhancement. (AU) Copyright © 2018 Companhia Brasileira de Metalurgia e Mineração (CBMM) All rights reserved