Reconditioning of pistons

Pistons usually require replacement or reconditioning at fairly regular intervals even if the engine is operated under near-ideal conditions. Their service life is limited because they are mechanically and thermally highly loaded components, which over time suffer from excessive wear of the piston ring grooves and/or hot corrosion at the piston top surface.

Depending on the condition of a given piston, QuantiServ recommends either full or partial reconditioning.

Full reconditioning

The entire top surface and ring groove area is first machined off and then  rebuilt by either SAW or a combination of SAW and SMAW welding. Thereafter, the piston undergoes final machining before galvanic chromium plating or laser cladding of the ring grooves is carried out. The last step is grinding of the ring grooves, which completes the full reconditioning process.

If it is requested by the customer, then we can coat the top of the piston by a protective layer of Inconel. This can be a good solution for engines that suffer from rapid hot corrosion at the piston top.

Partial reconditioning

If only the ring grooves are worn and if a piston is in otherwise good condition, then partial reconditioning is possible. A precondition is, however, that none of the ring grooves has worn so much that not only the chromium layer but the steel substrate itself has worn. In this case, partial reconditioning is not possible and full reconditioning is the only remedy.

During partial reconditioning, any remaining chromium is removed before the ring grooves are plated anew. The landing surfaces will be skimmed to remove any signs of fretting corrosion and if there are small, internal cracks, then they will be repaired too.

Laser cladding

With the introduction of the laser cladding technology, QuantiServ has redefined the piston reconditioning process. The laser cladding technology for two-stroke pistons was developed by QuantiServ and offers the following important  advantages:

  • Fully automated process carried out by a robot. This results in a top-quality product due to very high accuracy, repeatability and consistency.
  • Faster than chromium plating, therefore shorter turnaround times.
  • Less heat input into the piston, eliminating any residual stresses.
  • Environmentally sound, non-toxic process.

Laser cladded ring grooves are far harder than chromium plated ones. Accordingly, life times and therefore time between overhauls (TBOs) are achievable today that were far out of reach even one or two years ago. We are today able to guarantee a ring groove life time of up to 24,000 running hours on our reconditioned pistons!

Laser welding piston 1
Fully robotized laser welding of a piston
Fully robotized laser welding of a piston
NC Machining of a piston after welding
NC Machining of a piston after welding

Image Gallery

Final machining on a CNC machining centre
Final machining on a CNC machining centre
Robotized laser-cladding of the piston ring grooves
Robotized laser-cladding of the piston ring grooves
Robotized welding
Robotized welding
Pistons during processing
Pistons during processing
Submerged arc welding of pistons
Submerged arc welding of pistons
Laser-cladded piston ring groove
Laser-cladded piston ring groove