Research On The Properties Of Ni/TiC Coating Synthesized By HFIH/SHS

In this paper,TiC-Ni cermet composite coatings with different Ni content of(10wt.%~50wt.%)were prepared on the 5CrNiMo steel by high-frequency induction heating/Self-propagating High-temperature Synthesis(HFIH/SHS).The microstructure and phase composition of the coating were analyzed by SEM and XRD,respectively.The surface hardness and cross-sectional hardness of the coating were measured by a microhardness tester.The porosity of the coating was measured by Image-pro Plus(IPP),a professional image analysis software.The corrosion behaviors of the coatings(10wt.%-30 wt.% Ni)in molten aluminum alloy and copper alloy and thermal fatigue behavior of the coatings(10wt.%-30 wt.% Ni)were analyzed by immersion test and thermal fatigue test.The main conclusions are as follows:1.The heating frequency used in the experiment is 50 KHZ,the pressure is 25 Mpa,and the holding time is 40 s.Theoretical calculations show that the adiabatic temperature of the self-propagating reaction of Ti-C-Fe system is lower than that of the self-propagating reaction of Ti-C-Ni system.The adiabatic temperature of two reaction systems gradually decreases with the increase of Ni/Fe content.2.The coating prepared by(HFIH/SHS)method is well integrated with the steel substrate.The phase composition of the coating is mainly TiC and Ni.With the increase of Ni content,the grain size of TiC gradually decreases and the distribution becomes more uniform.However,the internal porosity of the coating increases,the surface hardness of the coating increases firstly and then tends to a stable value.The cross-sectional hardness was 10 wt.%Ni<30wt.%Ni<20wt.%Ni.3.After 1h corrosion test,the corrosion resistance of 5CrNiMo steel substrate and TiC-Ni composite coating against aluminum alloy is not ideal.The failure depth of TiC-Ni is reached 100-200 μm.The failure mode of the coating is dominated by the corrosion of metal Ni.4.Corrosion resistance of TiC-Ni composite coating against copper alloy is better than that of 5Cr NiMo steel substrate.20 wt.% Ni coating has the highest anti-corrosion ability.Compared with corrosive test in molten aluminum alloy,the corrosion resistance of the coating in molten copper alloy is better than that in molten aluminum alloy.The failure of the coating is mainly the erosion of metal Ni and the oxidation of the TiC particles on the surface.5.After 500 thermal fatigue circles,the thermal fatigue performance of TiC-Ni composite coating is better than that of 5Cr NiMo steel substrate in the whole.Except 10 wt.% Ni coating,no cracks appear on the surface of other coatings.After 900 thermal fatigue circles,the coating will gradually fail.The thermal crack extends nearly 400-600 μm into the interior of the coating.The failure of the 10 wt.% Ni coating is more detrimental than the other coatings.The propagation of thermal fatigue cracks in the coating is a transgranular fracture through the TiC particles.