Research on sub-surface recrystallization of single crystal nickel-based superalloy in micro-milling

Abstract

The micro-structure/parts of single crystal nickel-based superalloy materials are extensively used in high temperature environments. The recrystallization mechanism of the machined workpiece sub-surface is explained through energy storage model. A micro-milling experiment of single crystal nickel-based superalloy DD98 was performed by simulating the working environment at high temperature and setting different heat treatment temperature. By scanning electron microscopy (SEM), the influence of sub-surface structural elements on the properties of micro-milling workpiece was analyzed. Experimental results indicate that the recrystallization layer thickness of single crystal nickel-based superalloy DD98 increases with the increase of heat treatment temperature. When this temperature is between 950 °C and 1150 °C, the recrystallization thickness is 5–20 μm. The recrystallization of sub-surface layer takes the form of equiaxed recrystallization. Those provide basic data for restraining recrystallization of single crystal materials and have good scientific significance.