A Match of Material and Process: a Slip for Downhole Isolation Tools Made of a Cast Iron by Surface Hardening Treatments

In the design of a downhole isolation tool for multi-stage fracturing in oil and gas industry, a setting component, called slip, was used to set the tool in the casing prior to hydraulic fracturing operation. The material of the slip is made of gray cast iron with surface hardening requirement. This study demonstrated the slips treated by induction hardening versus flame hardening. The slip treated by induction hardening produced low hardness and insufficient affected layer. On the other hand, flame hardening generated satisfied results of case hardening layer by 0.030” thickness with 50 HRC minimum. The type E graphite in the raw material was transformed to type A in the flame hardening process which is favored in the case hardened layer. The effect of different treatment processes on the affected layer and their microstructurual response in gray cast iron was discussed in this study. The isolation tool using the slip treated by flame hardening, together with other proven components, showed successful performance of 12 ksi pressure holding at 350°F for HPHT downhole application.