Diesel engine operation under high load conditions (>45 hp/cyl) may result in piston “debond” in which the Ni-resist ring carrier separates from the aluminum piston matrix leading to destruction of the piston.
Historically, engine loads have increased to achieve higher power densities which together with more stringent emissions requirements have resulted in greatly increased stress levels in the piston. The higher stresses have resulted in debond failure.
The design of the ring carrier will affect debond failure. Deformation of the ring carrier will initiate debond at the back of the insert at the junction with the piston matrix. The ring carrier cross-section must be made robust enough through proper design to achieve expected reliability. Another factor influencing ring carrier retention is the quality of the AlFin bond layer. Casting defects which arise from the AlFin bonding process, degrade the strength of the joint leading to failure.
Practical methods to increase the durability of the AlFin bond layer are to conduct rigorous ultrasonic inspection to eliminate defects and to design the ring carrier to withstand expected engine loads.