Where is a nickel insert used in an aluminum alloy piston used by diesel engines?

• A. Piston crown
• B. Wrist pin boss
• C. Compression ring groove
• D. Oil control ring groove

Answer: (C)

In diesel engines with aluminum pistons, the places where the piston rings ride must resist a lot of wear and indentation from the moving rings under high pressure. A nickel alloy insert in the compression ring groove provides a hard, wear-resistant surface specifically where the compression rings contact the groove. This helps keep the groove round, maintains a good seal, and reduces wear on the groove lips and ring faces over time. The crown is typically treated or coated to handle heat, and the wrist pin boss and oil control ring groove aren’t reinforced with nickel inserts in the same way, so the most effective and common location for the nickel insert is the compression ring groove.