Tribological Research On Lightweight Materials And Coatings

Automotive industries are under extreme pressure to meet the legislative demand for producing environment friendly vehicles as well as to satisfy customer's demands.The factors for the development of automotive engine technology involve environmental protection,resource utilization,customer satisfaction,etc.These challenges are directly related to the improvement of fuel economy that principally depends on the reduction of friction losses and weight reduction of engine components.This means materials technology and lubrication technology are two critical aspects that need to be solved in advanced engine techniques.For materials technology,the selection of lightweight materials is the key issue.As the demand of lightweight increases,together with the market request for compact superpower engine,cast iron no longer meet the standard of a new developed engine,which appeals for higher strength,hardness,stiffness,lower density and better tribological properties of the material.This put steel and aluminum on to the stage.As for lubrication technology,applying functional coating become a new approach for friction reduction.Some most common used coatings are nitrides,carbides,carbonitrides,DLC,ECC and PEO,etc.These coatings can not only protect surfaces but also reduce friction.In this paper,chain-on-disc tribometer and surface profiler were used for the comprehensive tribological properties of four alloys(CI-250,16MnCr5,Al-6061,DISPAL)and four coatings(DLC1,DLC2,ECC,PEO).Possible causes of their tribological behavior were analyzed,prospect of energy saving and emission reduction as well as priorities of application were given.Main conclusions can be drawn as below:(1)Under the condition of 945 A lubricant,ECC,DISPAL,16MnCr5 and DLC all showed lower friction than cast iron;(2)But under the condition of 948 A,only ECC,DISPAL and DLC2 exhibited relatively better comprehensive tribological properties.Considering costs and process,their priority should be ECC>DISPAL>DLC2;(3)Composition,microstructure and topography of a coating is of great influence for its tribological behavior,that's why DLC1,DLC2 showed various friction and wear behavior,and PEO exhibit highest friction coefficient;(4)Ingredients and viscosity of a lubricant are also critical,friction modifier and antiwear agent in the oil can promote its friction performance significantly;(5)Traditional aluminum alloys are not suitable for sliding part in engine for that they may suffer severe wear,problem could be solved by ECC or DISPAL alloy,but remember to control primary silicon when using DISPAL.