Study On Structure And Properties Of DLC Films Regulated By Pulse Bias

In recent years,diamond-like carbon(DLC)coating with excellent wear resistance,high hardness,self-lubricating property,high elastic modulus and biocompatibility has attracted much attention in the processing and manufacturing industry,especially the low friction performance has effectively improved the performance and service life of processing tools,making the new DLC coated tools gradually replace the traditional tools,and has been widely used in the cutting field.The better process parameters are one of the key factors of coating technology.Diamond like carbon(DLC)coatings were deposited by multi arc ion plating.The structure and properties of diamond-like carbon deposited with different pulse bias parameters(bias frequency,bias amplitude and bias duty cycle)were compared,and the better deposition process parameters were obtained.The surface morphology and thickness of DLC films were observed by scanning electron microscope(SEM);the change trend of sp~3 content in DLC films with process parameters was determined by Raman spectroscopy and X-ray photoelectron spectroscopy(XPS);the hardness and Young's modulus of DLC films were measured by nanoindentation.Then,the cutting experiments are carried out on the CNC lathe to compare the cutting performance of diamond-like carbon coated tools and uncoated tools from three aspects of cutting force,cutting heat and surface roughness after cutting.The results show that with the increase of bias frequency,the size of aggregates on the surface of the film decreases gradually,and the thickness of the film is basically the same at the same deposition time.The sp~3 content of DLC films deposited at low frequency is higher than that deposited at high frequency,and the hardness and Young's modulus of DLC films deposited at low frequency are higher than those deposited at high frequency.The best process parameter of bias frequency is 20k Hz.With the increase of bias voltage amplitude,the deposition rate first increases and then decreases,and the thickest DLC film is deposited at 80V bias voltage;the SP3content,hardness and Young's modulus also increase first and then decrease;the peak values of hardness and SP3 content are at 80V bias voltage and 100V bias voltage,respectively;from 100V bias voltage,the film collapses,and the grain sensitivity of the film surface becomes more obvious,and the surface quality becomes worse;the bias voltage increases gradually The optimum process parameter is 80V.With the increase of the bias duty ratio,the particles on the surface of the film become dense;however,the higher the bias duty ratio leads to the increase of aggregates,and the better duty ratio of the film is 0.5.The deposition rate,sp~3 content,hardness and Young's modulus of the films increase at first and then decrease,with the peak value in the bias duty cycle range of 0.5-0.6.Therefore,the best process parameter of bias duty cycle is 0.5.The cutting experiments of coated tool and uncoated tool are carried out on CNC lathe.The cutting force and cutting temperature in three directions are measured with dynamometer and infrared thermometer.The surface roughness of workpiece after cutting with two kinds of tools is measured respectively when the cutting is finished.It is found that the coated tool is better than the uncoated tool in all aspects.