Preparation Process And Microstructure Properties Of The NiCrBSi-TiN Composite Gradient Coating

In order to prepare the wear-resistant belt of drill pipe joint with high wear resistance,the Ni Cr BSi-Ti N composite coating with different Ti N content was prepared by reactive plasma spraying.The microstructure,microhardness and friction and wear properties of the coating were studied,and the material of the surface layer of the wear belt coating was determined.And then the effect of induction remelting process on the microstructure and properties of a Ni Cr BSi-Ti N composite coating with Ti N content of 30% was studied.Finally,the Ni Cr BSi-Ti N gradient coating was successfully prepared by reactive plasma spray in situ induction remelting process,and its microstructure and properties were studied.The results showed that:The change of Ti N content in Ni Cr BSi-Ti N composite coating has little influence on the Webb characteristic value of microhardness,but the influence on Webb modulus was more obvious.When the content of Ti N was 30%,the Webb modulus of the composite coating was the largest,the microstructure of the coating was the most uniform and the mechanical stability was the best.The change of Ti N content had no significant effect on the friction coefficient of the Ni Cr BSi-Ti N composite coating,but the wear volume in the wear process has been significantly changed.When the Ti N content was 30%,the composite coating showed the best friction and wear resistance.Therefore,the Ni Cr BSi-Ti N composite coating with a Ti N content of 30% was selected as the surface working layer material of the wear-resistant belt.Induction remelting made the Ni Cr BSi-Ti N composite coating had a heat affected zone with a thickness of about 150 m.In the heat affected zone,the matrix organization slightly grew,and the change was not obvious.The internal micro cracks in the Ni Cr BSi-Ti N composite coating basically disappeared after induction remelting.The white spot with a thickness of 5-10?m appeared at the interface between the coating and the substrate.The interface element scanning between the coating and the substrate showed that the elements in the region had interdiffusion,which proved the formation of metallurgical bonding.The interface between Ni-based alloy and Ti N disappeared.The two phases could almost completely wetting each other.After induction remelting,the hardness of the Ni Cr BSi-Ti N composite coating was higher than that of the coating before remelting.The toughness of the composite coating increased significantly as a result of induction remelting.The friction coefficient of the composite coating decreased obviously after induction remelting.The fluctuation range of the coating during the stable wear stage was smaller.The wear resistance and antifriction performance of the composite coating was significantly improved after induction remelting.The average elastic modulus of Ni Cr BSi-Ti N gradient coating prepared by reactive plasma spraying was significantly higher than that of 30%Ti N composite coating with the same thickness.Meanwhile,the bonding strength and tenacity of Ni Cr BSi-Ti N gradient coating were obviously higher than that of 30%Ti N composite coating.The gradient coating produced by plasma spraying after induction remelting process was homogeneous and dense,and the microhardness of gradient coating was high The gradient coating showed good wear and antifriction performance.Therefore,the wear-resistant belt of the drill rod joint is prepared by selecting the gradient coating method.