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

摘要

Various coatings, especially nickel based ceramic composite (NCC) coatings, have been considered as an alternative to the use of iron plating on aluminum pistons in aluminum cylinder bore engines. Laboratory simulation tests were conducted to determine the scuffing and wear behavior of piston coatings 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 Si_3N_4, as well as titanium nitride physical vapor deposition (PVD) coating, diamond-like carbon (DLC) coating, and hard anodizing. The scuffing and wear resistances of these 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 Plint High Frequency test machine with a special fixture to hold the piston samples. Scuffing tests were conducted under the conditions in which lubricant starvation occurred. Metallographical work and chemical analysis of the interactive surface layers were performed on the tested samples. The simulation test results ranked the relative performance of the coatings against 390 Al bore, and revealed their tribological characteristics. Ni-P-BN coating, iron plating and Ni-W plating showed very good scuffing resistance when sliding against 390 Al bore samples. DLC, electroless Ni plating and Ni-P_SiC coating had moderate scuffing resistance against 390 Al. Ni-P_Si_3N_4 and TiN coatings had marginal scuffing resistance against 390 Al. TiN PVD coating had the most severe wear on 390 Al bore samples. Hard anodizing, DLC, Ni-P_SiC and Ni-Si_3N_4 coatings had less severe wear on 390 Al than TiN coating. With very good wear resistance themselves, Ni-W plating, electroless Ni plating, iron plating and Ni-P_BN coating produced the least wear on 390 Al. Engine dynamometer tests were conducted to confirm the simulation test results. This work indicates that the scuffing and wear bench simulation tests can be used as a rapid, low-cost and repeatable means of screening and studying the tribological behavior of the potential material combinations of piston coatings and cylinder bores.