Investigation On Properties Of The TiMoN Coatings Deposited By Arc Ion Plating

An increasing number of novel materials have been applied for product design in recent year.Coatings for cutting tools with high hardness and wear resistance are required due to the emergence of difficult-to-cut materials.Meanwhile,thermal stability and oxidation resistance are the important requirement for high-speed cutting.The high friction coefficient of traditional nitride coatings results in poor wear resistance.Previous studies have demonstrated lower friction coefficient can be obtained in Ti Mo N coatings.The adhesion strength,deposition rate,hardness and friction coefficient of Ti Mo N coatings can be improved by optimizing the nitrogen pressure and substrate bias process parameters of arc ion plating.Based on the high-quality Ti₉₂Mo₈ alloy target,this thesis prepared Ti Mo N coatings on YG6X cemented carbide by arc ion plating,and explores the influence of nitrogen pressure and substrate bias on the key properties of Ti Mo N coatings,such as adhesion strength,deposition rate,hardness,friction coefficient.The oxidation resistance and thermal stability was investigated based on the best deposition process.The main findings of this thesis are as follows:?1?The nitrogen pressure has a great influence on the properties of Ti Mo N coatings.The surface roughness of Ti Mo N coatings decreases with increasing nitrogen pressure,and reaches a minimum value of 0.664?m when the P_N2?nitrogen pressure?is 1.8 Pa.The nitrogen content is proportional to nitrogen pressure.Fcc-Ti N and tetragonal Ti₂N phases are detected in low nitrogen content coatings,while the high nitrogen content coatings has a single-fcc structure.Molybdenum is present as solid solution in Ti Mo N coatings.The thickness of Ti Mo N coating is first increased and decreased along with increasing nitrogen pressure,and reaches a maximum value of 2.44?m when P_N2 is 0.6 Pa.The hardness of Ti Mo N coating is first increased and decreased and then increased again along with increasing nitrogen pressure,and reaches a maximum value of 36.56 GPa when P_N2 is 0.28 Pa.Excellent toughness is performed by Ti Mo N_X coatings.Single-phase coatings performed higher toughness than dual-phase coatings.High adhesion can be obtained at high P_N2,and the L_C2>100 N when the P_N2 is 0.6 Pa,1.2 Pa,1.8 Pa.The coefficient is 0.208?0.385 and reaches a minimum value when P_N2 is 0.6 Pa.The formation of Mo O₃during the wear process is the main lubrication factor of the Ti Mo N coating.Ti Mo N coatings have good corrosion resistance.The I_corr reaches a minimum value of3.6658í10^-9 A/cm² when P_N2 is 0.6 Pa.TEM results show that the deformation mechanism of the Ti Mo N coating is dominated by dislocation and grain boundary sliding,and the auxiliary mechanism is twin deformation.?2?Surface roughness decreases as the substrate bias increases.Two phases are detected by XRD in coatings deposited at different substrate bias.At higher substrate bias,the?111?preferred orientation of the coating disappears.The thickness of the coating first increases and then decreases as the substrate bias increases,and reaches a maximum value of 2.44?m when the substrate bias is-100 V.The mechanical properties of the coatings are reduced in too high or too low substrate bias,and reaches the best with hardness of 34.26 GPa when the substrate bias is-100 V.Higher substrate bias results in reduced toughness.Lower substrate bias can result in smaller L_C2,which fall to 67.85 N when the substrate bias is-50 V.The friction coefficient of coatings deposited at different substrate bias is slightly higher than 0.2.When the substrate bias is-100 V,the coating reaches lowest friction 1.216í10^-6 mm³/N×m.The coatings perform good corrosion resistance deposited at different substrate bias.?3?After annealing at 300?500?in Ar,the phase structure of Ti Mo N coating changed from dual-phase to single-phase with disappearance of Ti₂N phase.The initial oxidation temperature of Ti Mo N coating is 400?,and is oxidized severely at 500?.The hardness of Ti Mo N coatings reaches 27.21 GPa after annealed at 500?in Ar.The toughness of annealed coatings is consistent with as-deposited coating.High hardness and toughness of Ti Mo N coatings can be maintained in high temperature.