Study On Surface Strengthened Mechanism Of WC-Ni Hard Alloy Coatings Irradiated By High-intensity Pulsed Ion Beam With Temperature Increased

WC-12Ni cemented carbide coating(the thickness is 200 ?m)was prepared on 17-4PH stainless steel substrate by High velocity oxy-fuel(HVOF)technology.Then the TEMP-6 HIPIB device was used to irradiate the WC-12Ni cemented carbide coating.The shot numbers is 1,5 and 10 and the initial temperature of irradiation is 25 ?,200 ? and 400 ?.The surface of samples was heated to 200 ? and 400 ? through heating furnace control heating device.After the experiment,the surface morphology and roughness,cross section morphology,surface phase structure,surface microhardness,microhardness depth distribution and porosity of the WC-12Ni cemented carbide coating before and after irradiation were analyzed and measured,and the variation rules of the sample with irradiation times after irradiation were studied.The aim is to explore the surface strengthening mechanism of high intensity pulsed ion beam irradiated by WC-Ni hard alloy under elevated temperature.A strong current pulse ion beam with an energy density of 7 J/cm2 and a pulse width of 70 ns was produced by using a self magnetic insulating ion diode with graphite as an anode.The WC-12Ni hard alloy coating samples of the coating thickness of 200 ?m were irradiated at room temperature of 25 ?,and the shot number is 1,5 and 10.After 1 irradiation,the surface of the WC-12Ni hard alloy coating appeared on the surface of the corrosion pit and crack,the Ra value of the roughness increased from the original 0.035 to 0.516 ?m,the original surface hardness is 10.1 GPa,and the decarbonization in a few WC phase changed to WC1-x phase and W2C phase,while the Ni phase was selectively ablated.With the increase of the number of irradiation,the surface roughness and hardness of the WC-12Ni cemented carbide coatings are increasing,but the surface is more compact and the pit is slowly decreasing.The hard phase WC phase of WC-12Ni cemented carbide coating is continuously transformed into W2C phase and WC1-x phase,and the bonding phase Ni decreases with selective ablation.When the number of irradiated times reaches 10 times,the surface of the WC-12Ni hard alloy coating produces a smooth,compact,wavy and undulating ablation remelting morphology,the Ra value of the roughness increases to 3.137 ?m,the surface hardness increases to 13.6 GPa,and the microhardness depth distribution of the coating becomes even more uniform because of the increase of the number of irradiated times.The depth of the layer increases first and then decreases,and the hardness depth distribution presents the structure near the surface and subsurface.Under the conditions of initial temperature of 200 ? and 400 ?,the irradiation experiments of WC-12Ni hard alloy coatings with the same experimental parameters irradiated at room temperature with the thickness of 200 ?m,respectively,were irradiated with the same experimental parameters at room temperature,and the number of irradiation times was 1,5 and 10.The surface morphology also shows a typical change process from the smooth and loose original morphology to the ablation crater and the crack to form the undulating remelting process,but the coating surface of the sample coating surface after radiation of 10 times at 400 ? at the initial temperature is more smooth in the micro area after 10 times irradiated at the room temperature.The surface roughness of the coating was,and the surface roughness of the coating reached 2.760 and 3.806 ?m after 10 shots.The phase structure of the coating surface also decreases with the increase of the number of irradiated WC phase to W2C phase and WC1-x phase,and the selective ablation of Ni phase decreases,but when the number of irradiated times is 10 times,more WC phase in the coating surface is converted to W2C and WC1-x phase under the initial temperature of 400 ?.The surface microhardness of the sample coating increased to 13.1 GPa and 14.9 GPa after irradiation for 10 times at the initial temperature of 200 ?and 400 ? respectively.The depth of the hardened layer of the coating increases with the increase of the number of irradiation.In addition to the structure,the second hardened peaks of the subsurface increase with the increase of the number of irradiation.