Microcracking of high-speed-steel tools during cutting

Abstract

Examination of both wrought and sintered T6 and M2 high-speed-steel cutting tools used in continuous-turning tests at cutting speeds of 15-60 m min⁻¹ has revealed the presence of microcracking at the tool nose. In wet-cutting conditions, the maximum average steady-state flank-wear rates at cutting speeds of 20–30 m min⁻¹ coincide with the appearance of cracks extending across the matrix through several carbides. At higher cutting speeds only individual carbides were broken, with little extension into the matrix. In dry-cutting conditions the wear land is smaller than in wet cutting, but consists of a rough cracked area. The cracks were present beneath the built-up edge, or just below it on the flank face. The generation of cracks under both wet- and dry-cutting conditions is discussed in terms of cutting speed, built-up-edge stability, and cutting temperature.