Aluminum block, cast in iron cylinder liners - Claimed issues

[jgattoni]

Hello, I am having a Mazda 2.3 liter blocks Iron cylinder liners Chromium Nikasil PVD Coated for a specific application where the engine will be subjected to corrosive (sulfuric acid) mixed gaseous fuels. They have responded and said that there is an aluminum lip (part of the aluminum block) at the top of the liner where it is cast into place and they cannot coat it because of 2 dissimilar materials. This makes no sense as they can nikasil coat aluminum OR iron no problem...and as far as there being a ridge after coating where the 2 materials meet, well I cannot imagine the top compression ring comes into contact with the aluminum in the first place...and I verified that the aftermarket pistons going in have the exact same compression height as the OEM pistons that were in there, as well as top ring placement in the piston with respect to the wristpin and top of piston. Do you see any issue here? They want to bore and install full length liners, and I have to say I disagree. Thanks.

 

[MikeHalloran]

Are you expecting 'they' to warrant your engine's survival?

Mike Halloran
Pembroke Pines, FL, USA

 

[dgallup]

The coating process may be significantly different depending on the substrate.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[140Airpower]

You cannot expect the coating to bridge two different materials without cracking. There would be subsequent penetration of corrosives. If that didn't happen, the 3-metal ring of contact should produce a galvanic cell.

 

[tbuelna]

Nikasil is not applied using PVD. It is applied using an electrochemical process. The nickel plating infused with silicon carbide particles is first applied with an electrode that is conformal to the bore. Then the nickel plating surface is chemically etched leaving behind silicon nitride particles attached to a nickel substrate. Lastly, the silicon nitride particle surfaces are diamond honed to produce a super-hard wear surface surrounded by valleys that retain lube oil.

 

[azmio3]

just curious. Back in the 90s, we moved from nikasil coating to hypereutectic blocks because the nikasil coating got severely compromised by high sulfur fuel in various markets. Iron liner is a bullet proof solution for an aluminum block thus I am wondering why nikasil coating is needed in the first place?

 

[Marquis]

In my experience Nicasil was a big issue when there was high sulphur content in fuels. In terms of friction Nicasil vs iron liner- below 8500 rpm there is very little measureable difference in the real world. Once you start to rev to 10,000 rpm then there frictional differences become more apparent but there are other ways to reduce friction

http://www.auto-scape.com

Sideways To Victory!