Scuffing and wear behavior of aluminum piston skirt coatings against aluminum cylinder bore

Various coatings, especially nickel based ceramic composite (NCC) coatings, have been considered as an alternative to the use of iron plating on alumi num pistons in aluminum cylinder bore engines. Laboratory simulation tests were conducted to determine the scuffing and wear behavior of piston coatin gs against 390 Al engine cylinder bore. The tested piston coatings included nickel-tungsten (Ni-W) plating, electroless Ni plating, Ni-P coatings with ceramic particles such as boron nitride (BN), SiC, or Si3N4, as well as ti tanium nitride physical vapor deposition (PVD) coating, diamond-like carbon (DLC) coating, and hard anodizing. The scuffing and wear resistances of th ese coatings were evaluated and compared with tin plating and iron plating. Wear tests were performed in lubricated sliding at 400 K, using a modified Cameron Flint High Frequency test machine with a special fixture to hold t he piston samples. Scuffing tests were conducted under the conditions in wh ich lubricant starvation occurred. Metallographical work and chemical analy sis of the interactive surface layers were performed on the tested samples. The simulation test results ranked the relative performance of the coating s against 390 Al bore. and revealed their tribological characteristics. Ni- P-BN coating, iron plating and Ni-W plating showed very good scuffing resis tance when sliding against 390 Al bore samples. DLC, electroless Ni plating and Ni-F-SiC coating had moderate scuffing resistance against 390 Al. Ni-P -Si3N4 and TiN coatings had marginal scuffing resistance against 390 Al. Ti N PVD coating had the most severe wear on 390 Al bore samples. Hard anodizi ng, DLC, Ni-P-SiC and Ni-Si3N4 coatings had less severe wear on 390 Al than TiN coating. With very good wear resistance themselves, Ni-W plating, elec troless Ni plating, iron plating and Ni-P-BN coating produced the least wea r on 390 Al. Engine dynamometer tests were conducted to confirm the simulat ion test results. This work indicates that the scuffing and wear bench simu lation tests can be used as a rapid, low-cost and repeatable means of scree ning and studying the tribological behavior of the potential material combi nations of piston coatings and cylinder bores. (C) 1999 Published by Elsevi er Science S.A. All rights reserved.