Analysis and Elimination of High Temperature Notch Induced Microcrack Initiation in Inconel 718 Nickel-Based Alloy
SAN ANTONIO AIR LOGISTICS CENTER KELLY AFB TX
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A mechanism for eliminating high temperature notch induced microcrack initiation within Inconel 718 was formulated by correlating the dislocation theory of precipitation hardening with plane stress experimental results obtained at elevated temperatures. Elimination of notch sensitivity was found to be possible by means of innovative treatment that increased the average distance between precipitates in this alloy from 50 to 167 atomic spaces without a prohibitive reduction of yield strength. This distance modification is critical as it must be sufficient to enable dislocation line segments to pass between susceptible to notch induced microcrack initiation. This analysis revealed that it is the spacing and not the size of the precipitates that determine the yield point of Inconel 718.