Study on Formation of the Composite Coatings by Thermal Spraying

为了提高金属的耐磨性，研究了热喷涂复合涂层的形成方法。采用丝爆法和等离子喷涂法在低碳钢基体上涂覆各种材料，研究了涂层的耐磨性、附着强度、硬度等性能。(1)在不同的放电能量密度下形成Mo和WC-Co涂层。孔隙率等参数与涂层与基体的结合强度有关。(2)对于WC-Co涂层，随着放电能量密度的增加，涂层中Co含量降低，WC脱碳至W_<1-x>C, W_2C。(3) Ni-P合金渗透到WC-Co涂层中，涂层耐磨性明显提高。(4)当Mo含量为25 vol%时，WC-6.5%Co-Mo复合镀层的耐磨性最佳。等离子喷涂(1)喷涂后的Al_2O_3涂层表面覆盖PTFE。轧制磨损试验表明，PTFE-Al_2O_3复合涂层的磨损量明显小于Al_2O_3涂层。(2)在较低的温度和压力下对5℃WC-Co涂层进行HIP后处理。热处理后涂层的耐磨性是喷涂后涂层的3倍左右。(3)采用机械熔合法制备Ni-Al复合粉末，并在空气或真空中喷涂。这些粉末和涂层的性能与市售产品基本相同。(4)采用双阳极氩弧焊炬沉积WC-12%Co涂层。结果表明，在最佳条件下喷涂的涂层的耐磨性是传统空气等离子喷涂涂层的两倍左右。

Study on formation of the composite coatings by thermal spraying was done for the purpose of improving the wear resistance of metals. The mild steel substrates were coated with various materials by the wire explosion and plasma spraying methods, and the properties of coatings such as wear resistance, adhesion strength, hardness, etc. were investigated.1. Wire Explosion Spraying (1) The Mo and WC-Co coatings were formed with various discharge energy densities. The parameters such as porosity, etc. were correlated with adhesion strength between the coating a nd substrate. (2) Regarding the WC-Co coatings, it was clarified that the Co content in the coatings was lowered and WC was decarburized to W_<1-x>C, W_2C with increasing in the discharge energy density. (3) The Ni-P alloy was infiltrated into the WC-Co coatings, and then wear resistance of its coating was much improved. (4) The WC-6.5%Co-Mo composite coating had the most excellent wear resistance at the Mo content of 25 vol% when the WC-6.5%Co and Mo wires were exploded and sprayed alternately on the substrate.2. Plasma Spraying (1) The sprayed Al_2O_3 coating was covered with PTFE. The rolling wear test indicated that the PTFE-Al_2O_3 composite coating wore much less than the Al_2O_3 coating. (2) The s prayed WC-Co coating was post-treated with HIP at lower temperature and pressure than ordinary HIP treatment. Wear resistance of the HIP-treated coating was about three times as well as the as-sprayed coating. (3) Ni-Al composite powders were prepared by the mechanofusion process and were sprayed in air or a vacuum. The properties of these powders and coatings were almost the same as those of commercial ones. (4) The WC-12%Co coating was deposited with the aero-plasma s praying torch "Twin Anode alpha". The coating sprayed with the agglomerated powder under optimum conditions showed to have about twice wear resistance compared with the conventional air-plasma sprayed coating.