Effect Of Induction Heat Treatment On The Interface Of Titanium Alloy/Coated Nickel And The Friction Properties

Titanium alloy is a strategic metal for the development of aerospace and marine engineering in various countries.It has the advantages of corrosion resistance,high specific strength and specific stiffness.However,its low wear resistance limits its application range.Nickel,as a commonly used wear-resistant material,can effectively improve the wear resistance of titanium alloys and further expand the application prospect of titanium.In this paper,electroplating process was used to obtain pure Ni layer on the surface of TC4 titanium alloy.The effects of heat treatment methods,induction heat treatment time and temperature,on the interface structure was studied in detail.Thermodynamic and kinetic analysis method were used to explain the formation of intermetallic compounds and the friction and wear properties of the induction heat treated samples were discussed.The following conclusions were obtained:(1)The surface of the nickel plating layer was uniform without cracks.Before induction heat treatment,the interface of the TC4 titanium alloy/coated Ni was clearly visible without obvious cracks.The scanning analysis showed that no new phase was formed at the interface.(2)A comparative study was conducted at the interface of the samples subjected to induction heat treatment and resistance heat treatment:compared with resistance heat treatment,induction heat treatment significantly promoted the interdiffusion of Ti and Ni atoms and increased the growth rate of Ti-Ni intermetallic compounds under the same conditions.The interface diffusion area was wider,which can more effectively produce more Ti-Ni intermetallic compounds.(3)With the increase of induction heat treatment time,the interface structure was Ni₃Ti and NiTi phase at heat treatment 10 minutes,which can be transformed to Ni₃Ti,NiTi and NiTi₂ at heat treatment 30min and 60min.A certain incubation period was required to produce NiTi₂ phase.(4)At 30 minutes of induction heat treatment,the interface structure was Ni₃Ti and NiTi at 750?,while the interface structure was Ni₃Ti,NiTi and NiTi₂ at 850?and 950?.The higher the temperature,the shorter the incubation period of NiTi₂,which may be due to the rapid growth of NiTi phase which consumed a large amount of NiTi₂ at the early stage,resulting in no residual NiTi₂ phase.In the late stage of induction heat treatment diffusion,the growth of NiTi phase consumed a large amount of Ni₃Ti phase.(5)The free energy of Ti-Ni intermetallic compounds were all negative,and their order of magnitude was NiTi>NiTi₂>Ni₃Ti,and their order of formation enthalpy was Ni₃Ti>NiTi₂>NiTi.However,in this paper,the NiTi phase was generated before the NiTi₂ phase.This was because the eddy current at the NiTi phase was larger than that of NiTi₂,the atoms were more activated.(6)With the increase of heat treatment time,the growth rate of Ni₃Ti,NiTi and NiTi₂intermetallic compounds gradually diminished,however,NiTi phase growed fastest,while NiTi₂ growed slowest.The growth curve of the NiTi and NiTi₂ phases was consistent with the parabolic equation.However,the growth of the Ni₃Ti phase only accorded with the parabolic equation at a short time after reaction.(7)The friction coefficient of the TC4 titanium alloy substrate was 0.59,however,the friction coefficient of the sample after induction heat treatment was 0.29,and the wear loss was reduced by 64%.And there were a large number of small furrows on the wear surface of the titanium alloy TC4 substrate.The worn surface of the sample after heat treatment showed obvious plastic rheological characteristics,and the coating significantly improved the wear resistance after induction heat treatment.