Effects Of Mo And Cu On Microstructures And Properties Of Ni60A Layers Produced By Plasma Spray Welding

Working conditions of many parts are quite harsh in the field of mining, die casting and etc., corrosion and wear are the main reasons for parts, failures. Surface strengthening techniques such as laser cladding and plasma spray welding are used by researchers to improve the surface wear resistance, corrosion resistance and prolong service life for metal parts. The plasma spray welding possesses advantages such as low material consumption, high production efficiency and etc., which is used by the industry.The layers on H13 die steel were prepared by plasma spray welding with Ni60A-based alloy powders. By adding alloy element Mo and Cu separately, the wear resistance and corrosion resistance of the layers were investigated. The effects of heat treatment on microstructures and properties of Mo reinforced layers that were treated by solution and aging were investigated.The microstructures of the layers became refiner and hard phases such as Mo Si2, Mo2 C, Mo3C2 and Mo C that distribute uniformly with the addition of Mo were formed in the layers. Mo3C2 were transformed into Mo C and Mo2 C by eutectoid reaction and these carbides present oval shape in the layers. Almost all primary carbides dissolved but Mo2 C and Mo C remain in the substrate. The coarse grain belt in fusion zone had disappeared and the chemical compositions of fusion zone became more uniform after solution treatment.The wear experiments showed that the wear resistance was increased by 30% compared with the Ni60 A layer when the addition of Mo reaches 8%. The wear resistance of the layers could decrease by adding excessive Mo. The microstructures and compositions of the layers became more uniform and the residual stress significantly decreased after solution treatment. The wear resistance of solution treated Mo reinforced layers got better compared with other layers.The electrochemical corrosion experiments showed that the pitting corrosion resistance of 8%Mo/Ni60 A layer got better. The Eb of 1%Cu/Ni60 A layer increased 80 m V compared with the Ni60 A layer and that possesses excellent pitting corrosion resistance. The pitting corrosion resistance of adding Mo and Cu layers was much better than that of 304 stainless steel. The further study revealed that 10%Mo+1.4%Cu/Ni60 A layer had the best pitting corrosion resistance. Meantime, the uniform corrosion resistance of adding Mo and Cu layers had improved in 10% HCl and 10% H2SO4 solution. The Ecorr of the layer increased by 69.6 m V after solution treatment in 10% HCl solution, indicating the better corrosion resistance.