Study Of Preparation Of Low Nitrogen W(N) Nanostructure Coatings By Magnetron Sputtering And Plasma Nitriding On H13 Steel

With the rapid development of modern manufacturing industry,the working conditions(impact load,friction and wear,etc.)of molds become more and more severe.The failure from the surface of the die greatly shortens the life of the die.Therefore,in addition to improving mold raw materials,the use of surface strengthening technology to improve mold surface hardness and wear resistance,so as to extend its service life is also very important.The integrated innovation research of plasma nitriding technology?advanced surface coating technology can provide an alternative solution for mold quality improvement and life extension.In terms of mold coating,W(N)coatings have the potential to be hard coatings with high hardness and good wear resistance,which is expected to replace Ti series and Cr series coatings to be the more favorable protector for the mold.In this paper,the effect of ion bombardment pretreatment on the microstructure and properties of arc plasma-assisted nitriding layer was carried out on H13 steel,and magnetron sputtering(High Power Impulse Magnetron Sputtering(HiPIMS),Direct Current Magnetron Sputtering(DCMS))was systematically studied.The main research content includes:(1)the effect of ion bombardment pretreatment on the structure and performance of the nitritic layer.(2)explore the effect of N solids? pulses on the structure and performance of the W(N)coating.The abrasion resistance and corrosion resistance of the nitride layer and coating are studied.The results show that the nitriding layer is composed of ?-Fe and ?-Fe3 N.The thickness of the nitriding layer increase with the increase of the pretreatment time of ions bombardment.The thickness of the compound layer range from 1.0 to 1.5 ?m,and the diffusion layer range from 12.3~21.8 ?m/h.The N content in the nitriding layer of the sample after ion bombardment for 90 min was up to 10.29 wt.%.The brittleness grade of nitriding layer of the sample is all first grade.The self-corrosion current density of nitriding samples are one order of magnitude lower than that of the substrate,indicating that the nitriding samples improved the corrosion resistance of the samples.The average friction coefficients of nitriding samples range from 0.68 to 0.75(pair of grinding Si3N4 balls).The wear amount of nitriding samples is smaller than that of the substrate,indicating that the wear resistance of the samples has been improved.The atomic ratios of nitrogen doped HiPIMS W(N)coatings and nitrogen doped DCMS W(N)coatings are W95.95N4.05 and W94.54N5.46,respectively.There is a small amount of O in HiPIMS pure W coatings.The coatings under different processes were all composed of ?-W phase.The preferred oriented crystal surfaces of nitrogen doped HiPIMS nano W(N)coatings,HiPIMS pure W coatings and nitrogen doped DCMS nano W(N)coatings are(222),(110)and(211),respectively.The grain average sizes of the three coatings were all at the nanometer level(4.4~21.5 nm).The nitrogen doped HiPIMS nano W(N)coatings had the smallest grain size at 4.4 nm.The deposition rates of nitrogen doped HiPIMS nano W coatings,HiPIMS pure W coatings,and nitrogen doped HiPIMS nano W(N)coatings are 2.6 ?m/h,0.8 ?m/h,and 0.6 ?m/h,respectively.The nitrogen doped coatings prepared by HiPIMS have the highest hardness(29.73 GPa)and the best toughness.The adhesion of the nitrogen doped DCMS W(N)coating is more than 100 N,while the adhesion of nitrogen doped HiPIMS W(N)coating is only 54 N.The average friction coefficient of the coatings range from 0.44 to 0.53(pair of grinding Si3N4 balls).Nitrogen doped HiPIMS W(N)coatings have the best wear resistance.The corrosion resistance of different coating are better than that of the H13 steel substrate.At different duty cycles(2.9%,3.8%,5.8%),the surface of the coatings are dimplelike.The coatings are all composed of ?-W phase with the preferred orientation of(222)surface.With the increase of duty ratio,the grain size of coatings decrease gradually,all at nanometer level(4.3~4.5 nm).The coatings thickness increase gradually and the deposition rate accelerate.The deposition rate of D5.8% coatings reach the maximum of 1.0 ?m/h.With the increase of pulse duty ratio,the hardness and elastic modulus of the coating increase.The coatings under the duty ratio of 5.8% had the highest hardness,reaching 31.11 GPa.With the increase of duty ratio,the binding force between the coatings and the substrate first increase and then decrease.The coatings with duty ratio of 3.8% have the largest binding force,reaching 54 N.The average friction coefficient of the coatings range from 0.33 to 0.44(pair of grinding Si3N4 balls).The wear mechanism mainly includes oxidation wear and adhesive wear,accompanied by a small amount of abrasive wear.After depositing the coatings,the corrosion resistance of the sample is obviously improved compared with that of the H13 steel substrate.