MECHANICAL AND THERMAL RESPONSE OF A NICKEL-BASE SUPERALLOY UPON GRINDING WITH HIGH REMOVAL RATES

The formation of a plastically deformed and a heat affected zone durin g grinding of superalloy IN738LC with a high depth of cut but slow wor k speed (creep feed grinding) was investigated. In order to obtain a b etter understanding of material removal mechanisms, the alloy strength and contact temperatures under typical machining conditions were eval uated. Temperature calculations comprised both the stationary equilibr ium between global heat input and heat transfer to the coolant, as wel l as flash-like pulses at small contact spots. As a result, it was fou nd that local melting at contact spots seems to be a rather common mec hanism during grinding of superalloys, leading to so-called white laye rs which can easily be observed on metallographic cross sections. Grin ding wheel topography has a significant influence on the maximum conta ct temperature and the width of the white layer. Sufficient cooling is very essential in limiting the width of the molten zone to few microm eters, which then is not critical in respect to mechanical properties. On the other hand severe damage was observed after creep feed grindin g without coolant. (C) 1997 Elsevier Science S.A.