Study On The Preparation And Performance Of Diamond Composite Coating

Diamond composite coating is an ultra-hard coating formed by the co-deposition of diamond and matrix metal,with good corrosion resistance and wear resistance.It is often used as cutting tools,grinding tools,such as grinding wheels,wire saws,cutting pieces,etc.It is widely used in the cutting of ceramics,plexiglass,stone,nonferrous metals and other materials.The thickness and bonding strength of the coating are important indexes that affect the performance of the coating.It determines the reliability and service life of the product to a great extent.At home and abroad in the electrochemical deposition of metal matrix corundum composite coating research field,on the preparation process,coating structure,coating properties and applications and other aspects of the research has achieved certain results.However,due to the deposition mechanism of electrochemical deposition,there are still great difficulties in the thickening and deposition of metal matrix composite coating.At the same time,the binding force between coating and matrix and the bonding strength between metal matrix and diamond and other composite doped phases need to be improved.In order to further improve the performance of metal matrix corundum composite coating and broaden its practical application field,it is urgent to carry out in-depth research on the above two aspects,as well as comparative and systematic research on various metal bases.In this study,electrochemical deposition method was used to prepare diamond composite coating on hard alloy matrix.Taking hard alloy as matrix and Watte plating solution as basic plating solution,multi-layer structure design method was used to improve the thickness of the coating to prepare Ni-diamond composite coating with thick film.Cu-diamond composite coating was prepared by high speed copper plating process.Cr-diamond composite coating was prepared by hard chromium plating process.XRD,SEM and EDS were used to characterize the phase structure,microstructure and composition of diamond composite coating.Firstly,the effects of current density,temperature,thickening time,cathode suspension mode,stirring speed and additives on the surface morphology of diamond composite coating,the amount of sand on diamond particles and the properties of friction and wear were investigated.The Ni-diamond composite coating was prepared by electrochemical deposition.The thickness of ordinary coating is about 30m,and the thickness of multi-layer structure coating is about 50m,nearly doubling the thickness.After 25 times of thermal shock,the crack width of ordinary coating becomes larger,and the crack of multi-layer structure coating only appears in the subsurface layer,but there is no crack in the surface layer.After2500m grinding of GCr15 by common coating and multi-layer structure coating,the gap between diamond particles in the common coating and matrix metal increases,and the Ni layer is broken nearby.In the multi-layer structure coating,the gap between diamond particles and matrix metal is still very small,only a few intermittent small cracks appear,and the nearby Ni layer is not affected.The wear rate of multi-layer structure coating is higher than that of ordinary coating.This indicates that the method of multi-layer structure design reduces the internal stress of Ni-diamond composite coating and achieves the thickening and deposition of metal matrix composite coating successfully.The interfacial bonding strength of the thickened Ni-diamond composite coating did not decrease,and the sand amount was more uniform and compact,and the grinding performance was better;Secondly,the Cu-diamond composite coating was prepared by means of high-speed copper plating and electrochemical deposition.After 25 thermal shocks,the crack width of the Ni-diamond composite coating increased,and no micro-cracks appeared on the surface of the Cu-diamond composite coating.The Ni-diamond composite coating and Cu-diamond composite coating respectively ground the GCr15 for 2500m,and the Ni layer near the diamond particles in the Ni-diamond composite coating ruptured,the gap between the diamond particles and the matrix metal in the Cu-diamond composite coating increased,and the nearby Cu layer all ruptured.The wear rate of Cu-diamond composite coating is lower than that of Ni-diamond composite coating.Although with low stress of the matrix metal Cu layer can improve the bonding strength of coating and base,but because of its soft texture,but also reduces the Cu-diamond composite coating grinding ability,the Cu-diamond composite coating of GCr15,Si₃N₄,304 stainless steel three material matching parts grinding,deeply discusses the Cu-diamond wear mechanism of diamond composite coating;Finally,the Cr-diamond composite coating was prepared by the transition layer of non-cyanide alkaline copper and hard chromium plating technology.After 25 thermal shocks,the crack width of the Ni-diamond composite coating increased,and the surface crack density of the Cr-diamond composite coating did not increase and the crack did not increase.The Ni-diamond composite coating and the Cr-diamond composite coating respectively ground the GCr15 for 2500m,the Ni layer near the diamond particles in the Ni-diamond composite coating broke,and the Cr layer gap near the diamond particles in the Cr-diamond composite coating was still very small.The wear rate of Cr-diamond composite coating is higher than that of Ni-diamond composite coating.This indicates that the low-stress Cu layer as the overcoating layer and the Cr layer with higher hardness as the matrix metal can improve the bonding strength between the coating and the matrix as well as the bonding strength between the metal matrix and the composite doped phases such as diamond,so as to improve the grinding performance of the Cr-diamond composite coating.The wear mechanism of Cr-diamond composite coating was studied by grinding GCr15,Si₃N₄ and 304 stainless steel.