Study Of The Mixing Technique Of Laser And Plasma Nitriding Titanium

Titanium nitride is a kind of multi-functional material. Its high hardness, high temperature-resistant, acid and basic resistance, wear resistance, very good electrical conductivity, and heat conductivity make TiN an interesting hard film. TiN are widely used to manufacture metal chinawares, cutting tools, mould, pot, electeric contact and coating meterial on the surface of metal. Many methods have been used to make titanium nitride, but they have different limitations in the applying in industry. Therefore we apply a new method--Mixing Technique of Laser and Plasma Nitriding Titanium.To know the property of plasma more clearly, we simulated the plasma beam with two models, hydrodynamic and Monte Carlo. The current voltage characteristic, relationship between flux and discharge, plasma intensity, torch shape, vibration frequency, ion number density, and emission spectrum of them were researched and discussed. The results agreed well with experiment. It was predict that when U>5.5kV (hydrodynamic) or U>6kV (Monte Carlo), the plasma gun can effectively provide the high energy active particles for the material surface modification.We have processed the surface of titanium by means of LPN in atmosphere. The treated samples were measured by XRD, SEM, and microhardness tester. The titanium nitrides were obtained by LPN, and the microhardness of the nitriding sample surface were enhanced. At the same experiment condition It can not only restrain oxidation, but also obtain better nitriding results by LPN than by mixing laser and heated nitrogen. In the appropriate conditions, the iron nitride quantity and nitriding depth increase, however, the surface roughness of surface increases when the laser power intensity increases. The relationship between iron nitride quantity and laser power intensity is linear ascending. The iron nitride quantity and nitriding depth decrease when the scanning velocity increases. Scanning velocity little influences the surface roughness. The relationship between iron nitride quantity and scanning velocity is square descending. The nitrogen plasma flow rate also has the effect on the nitriding result. When the flow rate>0.2m3/h, the nitride result was obtained. The nitriding result became better with increasing the flow rate, and when it was more than 0.8m3/h, the flow rate is saturated.To know the thermal stability of titanium nitrides obtained by means of LPN, we annealed the differet samples obtained in the differet conditions at 200℃-800℃for two hours. The treated samples were measured by XRD and optical microscope. When the anneal temperature was less than 600℃, titanium nitrides changed little. After the anneal temperature was 800℃, titanium nitrides decomposed partially. The thermal stability of the samples obtained by LPN is better than that obtained by physical vapour deposition and plasma immersion ion implantation.We have simulated the nitriding process of LPN using three models, Fick law, Monte Carlo and molecular dynamics. The simulation is based on model of center-of-mass system, and the temperature factor is inducted for laser temperature field. According to the theoretical model, the program was written by C language. The distribution of nitrogen ions in titanium was calculated under different laser power intensity, scanning velocity, nitrogen ion energy and angle of incidence. The simulating results agreed well with experiments. Using the molecular dynamics, the error was the least, while using Fick law, it was the most.Because interatomic potential for Ti-N system must be used during simulating with Monte Carlo and molecular dynamics, a new interatomic potential was developed. We developed the (2NN) MEAM potential for the Ti-N system based on the previously developed potentials for pure Ti and N. Some physical propertis were calculated. It was found that the potential gives a good agreement with experimental information or first-principles.