| In this topic, a kind of plasma spray powder and its coating was prepared for the purpose of solving the problem of the aluminum engine cylinder inner wall surface protection. Then the composition of the primary powder was optimization designed to improve the property of the coating. Whereafter, the microstructure and tribological performance in different condition was researched.A kind of iron based powder with high chromium content was selected primarily and its coating was deposited on aluminum substrate by plasma spray technology. Besides,316L stainless steel coating HT200grey cast iron block was also prepared as a reference. Tribological experiment was carried out using UMT-3multi-function friction and wear tester and the result showed that it is feasible to protect the aluminum engine cylinder inner wall surface with the selected high content chromium iron based coating.However, there were still some shortages for the coating in the preliminary test, such as low hardness and toughness, poor corrosion resistance and unreasonable microstructure. In order to solve these problems, optimization designed powder was developed and a new type of high content chromium iron based coating was deposited combining the characteristic of the plasma spray process. The coating was significantly strengthened and toughened. The average hardness of the coating increased from476.22HV0.1to664.94HV0.1. The corrosion resistance was improved evidently and no obvious signs of corrosion were found around the wear track of tribological test under corrosion condition. The coating was compact and the porosity was2.36%. The coefficient of friction(COF) and wear rate of the new type coating were both lower than that of the primary coating under the condition of air, oil and corrosive oil environment. The property of the coating became more stable.Coatings deposited with the piston ring material of chromium(Cr), chromium nitride (CrN), titanium nitride (TiN) and diamond-like carbon film (DLC) were selected to wear against the new type of high content chromium iron based coating. The Cr coating was prepared by electroplating and the CrN, TiN and DLC coating were prepared by physical vapor deposition(PVD). The friction experiment was carried out under the lubricant of engine oil. It showed that the coating of Cr and DLC could avoid serious scratches on the cylinder coating. A mount of enlarged pores connected with each other appeared on the cylinder coating when worn against the Cr coating. Nevertheless, there was almost no damage to the cylinder coating when worn against to DLC coating. Countless evident scratches and few slightly enlarged pores were found on the cylinder coating when worn against to CrN coating. TiN coating caused serious damage and a deep wear track with many deep grooves and cracks were left on the cylinder coating. In the tribological experiment, when the normal load was constent and change the frequency, the COF increased with the frequency under the lower load of1N and3N. The COF decreased with the frequency under the medium and high of10N,15N,25N and30N. When the frequency was constent and change the normal load, the COF decrease with the normal load increased under the frequency of2Hz,4Hz,5Hz and8Hz. The COF decreased and then increased with the normal load increased under the endpoint frequency of1Hz and9Hz. The numerical simulation result indicated that in the area encircled by both the whole scale of normal load and the medium and low frequency scale, the COF was about0.1with small fluctuation. In the area of medium load-high frequency and endpoint of load and frequency, the COF decreased extremely to the range of0.05～0.07. In the area of low load-high frequency, the COF increased seriously to the value of0.2. |
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