A Comprehensive Tool Wear Model

The mechanisms that control the wear rates of tool materials nay be separated into three regimes depending on the cutting temperature and the properties of the tool and workpiece materials. In the low temperature regime, mechanical wear processes such as abrasion are rate-controlling and the wear of the tool material is determined primarily by its hardness. At higher cutting speeds, corresponding to higher cutting temperatures, the solid solubility of the tool material in the workpiece becomes significant and the chemical stability of the tool material determines the wear resistance. In the machining of steel with titanium carbide, chemical dissolution wear predominates above a cutting temperature of approximately 600 C. The machining of steel with cubic boron nitride or the machining of superalloys with CBN or silicon nitride-based tool materials is performed above 1200 C, at which temperature the wear rate becomes diffusion-limited and both the chemical stability and the chemical diffusivity control the wear rate. diffusivity control the wear rate. While these phenomena are well understood qualitatively, a quantitative model of tool wear is needed as part of an expert system to select tooling, forecast tool wear and set tool inventories in CIMS. The abrasive wear model of Rabinowicz has been integrated with the chemical dissolution wear model of Kramer to provide an algorithm that predicts the wear rates of hard coating throughout the speed range of application of high speed steel and cemented tungsten carbide tooling.