Abstract: In order to improve surface strength of agricultural machinery key parts such as rotary blade and plough underatmospheric conditions, the heat released from the exothermic reaction of termite as an internal heat source, and plasmaarc column as an external heat source, the in situ synthesis of Al2O3-Ti(C,N)(AT composite materials) composite coatingwas prepared on Q235A steel specimen surface by reactive plasma cladding technology.Firstly, raw materials were thecheap thermite (iron oxide and aluminum powder), titanium powder, graphite powder, TiN powder and Ni60A powder,which were mixed in a planetary type ball mill DQM according to the mass fraction ratio of Fe2O3∶Al∶Ti∶C∶TiN∶Ni60A= 36.5∶13.5∶8.4∶2.1∶4.5∶35, milled for 6 hours, was made a mixed powder paste with the self made glue which was theadhesive, and then was coated on the surface of pretreated Q235A specimen and the thickness was 2 mm±0.5 mm,reserving 2-3 mm arc end.Secondly, the sample was placed in the vacuum drying oven and were dried under 80 ℃ during12 hours, then cooled the sample to room temperature.Using the plasma arc column of DML-300 plasma welding machineas an external heat source, condition of the arc could be ignited successfully, increased appropriately the working distance(about 8 to 10 mm) and reduce the cladding current(120 A).The plasma arc single channel was used to scan the clad andreached thermite ignition temperature, then the thermite in the pre coated raw material occurred chemical reaction togenerate Al2O3 and Fe.After the first cladding operation was finished, it immediately reduced the operating distance andappropriately increased the cladding current, using the optimized process parameters: cladding current of 200 A, claddingspeed of 2.5 mm/s, preset coating thickness of 2.0 mm, ion gas flow of 0.6 L/min, working distance of 4 mm.Then the in situ synthesized Al2O3-Ti(C,N) composite coating was remelted and placed in Argon protection atmosphere cooling.Thecomposition, microstructure, phase and performance of Al2O3-Ti(C,N) composite coating were analyzed by scanningelectron microscope (SEM), energy disperse spectrometer(EDS), X ray diffractometer(XRD), micro hardness tester andfriction testing machine.The results indicated that the new phase Al2O3 and Ti(C,N) were synthesized in situ on Q235Asteel during the plasma cladding process and the composite coatings were made, which had a good metallurgicalcombination with Q235A steel substrate.The coating was mainly composed of reticular structure, nested structure andspherical structure.The hard phase Al2O3 and Ti(C,N) and Fe Ni binding phase were mutual inclusion between themselvesbody, nested within each other, constituting the spatial reticulate structure.The highest hardness value of the coatings wasup to HV0.52160, and the average hardness was HV0.51870, and about 7.7 times of Q235A steel substrate.The frictioncoefficient of AT composite coating was about 0.372 and the wear loss of the AT composite coating was about 1/7 of 65Mnsteel, and 1/17 of Q235A substrate surface.Compared with the substrate materials, the AT composite coating had higherhardness and more excellent friction and wear properties, which provided an experimental and theoretical reference for thesurface strengthening of agricultural machinery materials.