Study On The Deposition And Tribological Properties Of CrXN(X=Mo,Ti) Coatings By Arc Ion Plating Technique

The increasing demand for light weight and crash safety of automobiles has made high-strength steel with excellent performance gradually become the mainstream of automobile body steel,but it also brings new challenges to cold stamping dies.Because advanced high-strength steel materials have a high strength-to-mass ratio and better mechanical properties(strength and elongation)than conventional steel,the mold surface undergoes extreme contact pressure during the stamping process causing aggravates mold wear,which seriously shortening mold service life affecting surface quality of the workpiece and increasing the manufacturing cost of the car.The physical vapor deposition(PVD)hard coating with transition metal nitride as the mainstream is an effective measure to improve the service performance of precision stamping dies.The Cr N coatings exhibit excellent mechanical properties,anti-adhesion and corrosion resistance,and it has attracted wide attention.However,under the action of heavy load cyclic impact and high friction,the lower hardness of the Cr N coating is difficult to meet the requirements of use.In order to improve the friction behavior of automobile molds and the quality of stamping forming,this paper uses arc ion plating technology to successfully prepare self-lubricating and wear-resistant Cr Mo N coatings and high-hardness and wear-resistant Cr Ti N coatings on the mold steel substrate through a multi-element alloying method.The influence of deposition process,composition,structure,etc.on the structure and performance of alloyed coatings was systematically studied.The specific research results are as follows:(1)First,a series of Cr Mo N coatings were prepared by adjusting the negative bias voltage of the substrate(-50V?-200V).The Change of the substrate bias voltage significantly affected the structure of the Cr Mo N coating,which in turn changed the performance of the coating.The prepared coating is mainly(Cr,Mo)N solid solution phase.Properly increasing the negative bias voltage of the substrate is beneficial to rreedduuccee tthhee surface roughness of the coating,bbuutt the ion bombardment ability is enhanced,resulting in a decrease in the bonding strength of the coating.When the negative bias voltage of the substrate is-50V,the coating adhesion is optimal,reaching HF1 level,and the wear rate of the coating is lowest.(2)Cr Mo N coatings were prepared with different Cr Mo alloy targets,and the influence of Mo content(4.94 at.%?12.86 at.%)on the structure and properties of Cr Mo N coatings was studied.The thickness of the prepared coating is about 6?m.Due to the addition of Mo,the preferential growth of the Cr N(111)plane is inhibited and the orientation becomes random.Coatings with different Mo content have good bonding strength and can reach HF1 level.With the increase of Mo content,the hardness of Cr Mo N coating gradually increases.Cr_0.81Mo_0.19N has the best wear resistance and the lowest wear rate.(3)The Cr Ti N ternary coating was prepared by separating the target,and the influence of deposition parameters such as deposition pressure and substrate negative bias voltage on the structure and performance of the Cr Ti N coating was studied.The main phase structure of the coating is(Cr,Ti)N solid solution phase.All coatings have good bonding strength and can reach HF2 level.As the negative bias voltage of the substrate increases,the number and size of large particles on the surface of the coating can be effectively reduced,and the roughness of the coating can be reduced.With the increase of deposition pressure,the coating gradually showed a preferential growth orientation of(111)plane.When the substrate negative bias voltage is-50V and the deposition pressure is 3.5 Pa,the wear rate is lower,and its value is 3.57×10^-17m³/N·m.(4)In order to further improve the bonding strength of the Cr Ti N coating,the transition layer structure and multi-layer structure design were used to prepare Cr Ti N coatings with different structures.The hardness of Cr Ti N coatings with different structures is not much different,about 2600 HK_0.05.The multilayer structure can effectively reduce the surface roughness of the coating,and the smoother surface state is more conducive to improving the wear resistance of the coating.By increasing the thickness of the transition layer and the multi-layer structure,the bonding force is effectively improved to HF1 level,and the multi-layer structure has the smallest wear rate,which is 7.99×10^-17 m³/N·m.