Study On Process Microstructure And Properties Of Aluminizing Oxidation Coatings On Wear Resistant Cast Iron

Wear resistant cast iron is mainly used in car engines,combustion chamber and train brake system.It is usually invalidated by the intense friction or high-temperature oxidation in special working environment.Therefore,it is very significant to use surface technology to strengthen the high-temperature oxidation resistance and wear resistance of wear-resistant cast iron.This article takes the wear-resistant cast iron as the object of study,use the pack-aluminizing to prepare Fe-Al alloy layer in surface of cast iron.Subsequently,use in-situ high-temperature oxidation to prepare Al₂O₃ layer in surface of cast iron.The influence of the pack-aluminizing process parameters on the microstructure of aluminized layer was studied.The results show that the optimum process parameters of aluminizing are as follow:aluminizing temperature at 830?,aluminizing time for 3 h,and the pack powder mixture consist of 25%Al,2%NH₄Cl,2%CeO₂ and 73%Al₂O₃?wt.%?.Under the best aluminizing parameters,the thickness of aluminide layer may reach 95?m.The outer layer was made up of Fe₂Al₅ and the inner layer was made up of FeAl.The influence of the oxidation process parameters after aluminizing on the microstructure and the oxidation film was determined.The results show that the optimum process parameters of in-situ high-temperature oxidation are as follow:oxidation temperature at 1000?,oxidation time for 4 h.Under the best oxidation parameters,the film consists of?-Al₂O₃,and the thickness of the film is 850 nm.The performance tests show that:after conventional thermal oxidation treatment at750?for 100 h,the oxidation weight increase of original sample are 15 times as much as that of aluminized sample.The wear resistant cast iron after aluminizing and in-situ high-temperature oxidation significantly improve performance of surface of tribology,the abrasion loss of aluminized and in-situ high-temperature oxidized sample for 50 minutes is0.23 times as much as original sample.The wear mechanisms of oxidized layer are fatigue wear,appreciable wear and slight abrasive wear.