Composite electroforming of precision Ni-P-PTFE mold inserts with low internal stress and self-lubricating properties

Abstract

An electrolyte solution incorporating sodium saccharin and an alkynyl compound was provided to electroform Ni-P-PTFE mold inserts with both low internal stress and good self-lubricating properties. The results showed that with 5 g·L⁻¹ sodium saccharin and 1 mL·L⁻¹ alkynyl compound, the internal stress reached a minimum of −114 MPa, an 82 % reduction from the −646 MPa observed without additives. The presence of sodium saccharin and alkynyl compound in the electrolyte solution reduced the hydrogen evolution reaction current from 15.2 to 12.9 mA at the operating cathode potential of −1 V and decreased the RTC₍₁₁₁₎ from 100 % to 90 %. The reduction of internal stress in the electrodeposited Ni-P-PTFE composites was attributed to the decreased hydrogenation strain, diminished Ni (111) texture intensity, and the partial incorporation of alkynyl compound reaction products into the deposits, which weakened the connections between crystallites. Finally, 5 g·L⁻¹ sodium saccharin and 1 mL·L⁻¹ alkynyl compound was applied to electroform Ni-P-PTFE mold insert with micro features. Only slightly pile-up defects at the corner of grooves were observed on the polymer chips demolded from Ni-P-PTFE mold insert, demonstrating its good self-lubricating property.