Research On Preparation Of Copper Coated Iron Powder By Mechanochemistry

Copper clad iron powder（CCIP）is a kind of powder metallurgy material with copper saving,environmental protection and low cost.It has important practical significance and great industrial application value to develop qualified CCIP.However,the existing methods of mixed diffusion and electroless plating are limited in their further application due to their respective problems.Therefore,from the perspective of environmental protection,uniform coating and solid interface bonding,a new process for the preparation of CCIP by manochemistry is proposed in this paper,that is,the superfine copper oxide powder is coated on the iron powder by mechanochemical effect,then qualified CCIP is obtained by hydrogen reduction and sintering.The key point of preparing CCIP by manochemistry is to prepare qualified precursor Fe-Cu O composite powder.The oxidation-reduction reactions take place between Fe and Cu O under mechanical force.The reaction products are Fe₃O₄,Cu and Cu₂O by XRD analysis,which are consistent with the thermodynamic calculation results.It is this strong mechanical force that makes fine Cu O particles adhere to the surface of Fe particles uniformly and produce strong mechanical and reactive bonding.In addition,the results show that the surface structure of rough and porous iron powder,large particle size ratio(D_Fe/D_{Cu O}),appropriate ratio of ingredients and com posite time are more conducive to the composite of Fe and Cu O particles.Hydrogen reduction and sintering determine the formation and densification of copper coating,and the bonding of Fe-Cu phase interface.The results show that iron oxide and copper oxi de can be reduced effectively by H₂,and the new phase Cu preferentially nucleates at the contact position or the defects on the surface of Fe particles,and then crystallizes to form Fe-Cu phase interface.Moreover,increasing sintering temperature,reducing the particle size of Cu O and increasing sintering time can promote the diffusion process and densify the copper coating.Taking the coating rate as the test index,the orthogonal table L₉（3⁴）with4 factors and 3 levels was selected to design the test.By range and variance analysis,it is found that the primary and secondary order of influence of each factor on the coating rate is:composite time>ingredient ratio>sintering temperature>sintering time.The coating rate is not less than 95%,and the oating thickness can reach 2-5μm under the best combination of parameters（the ratio of iron powder and copper oxide powder is 3:1,composite time 20min,hydrogen reduction temperature 900℃,sintering time 1h）.At last,the bonding characteristics of Fe-Cu phase interface were studied.The results reveal that Fe and Cu meet the physical,chemical and mechanical compatibility,and the bonding of Fe-Cu phase interface composed of reaction bonding,wetting bonding and mechanical bonding ensures the solid interface bonding.The achievements of this work not only contribute to the study of the preparation of coated particles by mechanochemi stry,but also make a new attempt to explore an environmental,economic and feasible preparation process of CCIP.