Research Of Ni-P Gradient Coating And Ni-P/SiC Gradient Coating

Elctroless plating is a new important field in material science.With its good performance,electroless deposit is becoming concern at home and abroad.As one of key properties of coating,bingding force is the premise of other used properties and engineering application.Currently,coating binding force being general not high restricts further widen of electroless deposit application area.Elctroless plating Ni-P Alloy has good acid and alkali resistance and so on.However,due to Ni-P electroless deposit being cathode coating,once appearing porosity or other defects that may be aggravated the corrosion of substrate,which limits actual application of this technique.Firstly,various factors affecting phosphorus content of coating were investigated. we realized changes of total phosphorus by changing species of completing agent of plating bath and prepared low phosphorus coating(w3.86%),medium phosphorous coating(w7.64%)and high phosphorus coating(w11.09%)with completing agent acetic acid system,lactic acid system citric acid system separately.On the basis of above,designed and prepared L-M-H Ni-P and H-M-L Ni-P gradient coating.Secondly,performance test of gradient coating were made.Test data showed that H-M-L Ni-P gradient coating,is the best to the anti-corrosion under acidic conditions in the corrosion-resistant realm(Corrosion current 1.815e-006A)and higher hardness(685HV),L-M-H Ni-P is higher in the bingding force realm(91N).Thirdly,studied further on the Process of electroless composite plating Ni-P/SiC coating.On this experiments,designed and prepared composite graded coating of which the deposition amount of SiC adapts progressive increase in distribution from substrate to coating surface.A series of data indicated that Ni-P/SiC gradient coating has higher hardness(1015HV)and bingding force of 78N,Ni-P/SiC gradient coating is not good at the anti-corrosion under acidic conditions(Corrosion current 7.060e-006A).