Research On Performance Of F-DLC Application On Tire Mold

Hydrophobicity,bonding strength and hardness are the main properties of coating for tire mold.With good hydrophobicity and bonding strength,Teflon coating are widely used in tire model,however,it has poor durability due to its low hardness.Compared with Teflon coating,diamond-like carbon(DLC)has better hardness and higher bonding strength,but with lower hydrophobicity.Hydrophobicity of DLC can be enhanced by doping fluorine element(F)in the coating,but meanwhile,higher F content may affect other property of DLC significantly,such as harness and abrasive resistance.Under specified F content in the DLC coating,surface roughness is another factor that affects its hydrophobicity,bonding strength and hardness.To enhance the efficiency of F doping,the improvement of hydrophobicity and bonding strength by changing roughness of coating was investigated under specific F content in this study,and harness under varied roughness was also studied,the specific research contents are as follows:(1)Substrate(S35C)pretreatment and coating preparation.Firstly,50 substrates with different degree roughness were obtained using different pretreatment technology.And then F doping F-DLC coating with 20 mass% of F was coating on these substrates using Plasma enhanced chemical vapor deposition(PECVD)technology(2)Influence of roughness on the hydrophobicity of F-DLC.Hardness of F-DLC coating was measured by nano indentation,Roughness of coating was measured by white light interferometer.Water contact angle,alcohol contact angle and the surface energy were measured by contact angle meter.It is found that a substantial increase in roughness is beneficial to increase of the coating hydrophobicity,and water contact angle can reach 101.7 degrees when roughness of the coating is 1300 nm.(3)Influence of roughness on bonding strength of F-DLC.Bonding strength of five specimens with different roughness specimens was measured using scratch test,the experimental results indicate that the bonding strength of F-DLC increases with the increase of roughness when the roughness is less than 100 nm.For the first time load Lc1 maximum 1.45 N cracks,and for the first time off the film,the load Lc2 can be up to 2.03 N.Compared with the previous data,the bonding strength of F-DLC coating is slightly lower than that of DLC coating(Lc1=1.52 N,Lc2=14.73 N),but it is still better than Teflon coating Lc1=Lc2=0.76 N.(4)Characterization of the F-DLC coating hardness.Harness of three specimens withroughness below 50 nm was tested using indentation methods.Compared with the hardness of Teflon coating and DLC coating,the hardness of F-DLC is 14.3GPa,less than 18.9Gpa of DLC,but it is higher than 65.6MPa of Teflon.With the elastic modulus,it can be proved that the F-DLC coating has good ability to resist plastic deformation and elastic strain failure.After a detailed study in this paper,it found that the low hydrophobic of DLC coating can be modified using F doping.And the analysis on the hardness and bonding force indicate that replace Teflon coating with F-DLC in tire mold is feasible.