Study Of Coating Preparation Process On The 42CrMo Surface

In the process of industrial production,corrosion and wear is main failure forms of metal equipment and parts.It is often first start from the surface,resulting in failure of the parts.People have been put forward many kinds of surface treatment technology,to improve the organizational structure of the material surface.Recently,it is pay more attention to the thermal spraying.But materials are easy to produce pores and inclusions after thermal spraying treatment.Surface coating technique is to use polymer with special packing such as metal powder,ceramic powder and fiber composed of composite adhesive coating on the surface of parts.Compared with thermal spraying,adhesive coating surface have the high energy and material utilization ratio,it is low requirement of processing environment and working equipment;it have the thickness coating and it is easy to operate.But it is the low bonding strength of coating and substrate throw the surface coating technology,the coating is easy to fall off from the substrate surface,so it is necessary to strengthen pre-coating again,increase the bonding strength of coating and base,at the same time reduce porosity and cracks in the coating and improve the density of the coating.In the process of coating preparation,this paper selects the electric contact strengthening technology to strengthen the pre-coating.It is first choose several different bonding agent for the preparation of pre-coating,it have E-44 AB epoxy resin glue,sodium silicate,cellulose acetate and Ni based conductive adhesive.In the process of experiment,it is throw adjusting the bonding agent and metal powder addition amount,to find the appropriate ratio,made a certain electrical conductivity after the preparation of the coating and good bonding strength between coating and matrix,can carry out the subsequent electrical contact to strengthen experiment.On the way of preparation pre-coating,choosing brush method.It is the two main aspects at following.The one is based on brush method,Ni60 powder were deposited on substrate surface to form pre-coating.Then use electrical contact surface strengthening technology to strengthen pre-coating and the enhancement layers were formed on the substrate surface.It is focus on the influence of micro-structure and mechanical properties of the coating by the electrical contact strengthening technology,compares the thermal shock resistance of strengthened layer by the thermal spraying and electrical contact composite reinforcement technology to prepare Ni60 strengthening layer.The other is obtain Ni60 / WC pre-coating through brush method,then reinforce pre-coating by the electrical contact strengthening technology,it is focus on the influence of micro-structure and mechanical properties of the coating by the electrical contact strengthening in the different current,compared its performance with Ni60 strengthening layer.For the sample after the electrical contact strengthening,the cutting is made after metallographical specimen,the strengthening layer micro-structure analysis by super depth of field electron microscope;using scanning electron microscope(sem)to strengthen electric contact surface coating after scanning,to character the coating elements distribution and diffusion;the coating hardness measure by HXS-1000 type a micro-hardness instrument;the thermal shock test by SX2-4-10 type instrument.The results showed that the one is based on brush method,putting pre-coating on the substrate.Then use electrical contact surface strengthening technology to strengthen pre-coating and the enhancement layers were formed.It can get compact structure and no visible flaws strengthening layer on the surface of the 42 CrMo substrate.The coating micro-hardness distribution is relatively uniform after the electrical contact strengthening technology,the coating hardness is greater than before.Getting Ni60 pre-coating by normal brush,then strengthening the pre-coating by the electrical contact strengthening technology,compare to the thermal shock resistance of strengthened layer,it is same to the thermal spraying and electrical contact composite strengthened layer.To strengthen the Ni60 / WC pre-coating by the electrical contact strengthening technology in the different current.Add WC to Ni60 alloy powder,by comparing thermal shock resistance of Ni60 and Ni60/WC strengthened layer,it is not big difference between them.With the increase of electric contact strengthen current,coating porosity decreases,density increased.When the current value of 22 k A,the best bonding strength between coating and substrate.The average highest hardness by coating,the maximum is about 855 HV.