Study On The Application Of Ni-Mo-P-MoS₂-Si₃N₄Chemical Composite Plating On The High Speed Steel Tools

Electroless plating is gaining increasing attention because of its simple process, energyconservation and environmental protection as a sort of new metal surfact treatment technology. It rapidly ispromoted and applied in aerospace field, computer industry, mechanical industry and mould making due toits good abrasive resistance, lubricaing property and uniform film, and so on. MoS2nano-particles havegood antifriction performance, and Si3N4nano-particles have ultra-high hardness and good lubricatingproperty, they are added into plating solution of electroless Ni-Mo-P plating with higher hardness, in thisway, electroless Ni-Mo-P-MoS2-Si3N4composite coating was gained, and the wear-resisting property wereinvestigated. In this paper, in order to increase the high-speed steel tool life, electroless Ni-Mo-P-MoS2-Si3N4composite coating was deposited on its surface, and used to cut duralumin alloy like the high-speedsteel tool for contrast experiment, and a remarkable result has been gained.Ni-Mo-P plating possesses higher hardness and better wear-resisting property than Ni-P plating.In this paper, Ni-Mo-P plating with a series of Mo-P content were prepared by adding sodium molybdate ofdifferent amount into the plating solution of electroless Ni-P plating. In order to finding the electrolessNi-Mo-P plating with the highest hardness and best wear-resisting property, the relation between thewear-resisting property (and hardness) and Mo-P content in the plating were investigated bymorphological observation and detection of chemical component of the plating using Quanta200typeScanning electron microscope with Energy Disperse Spectroscopy, test of microhardness of the platingusing HXD-1000TM type microhardness tester, and test of friction and wear property of the plating usignMS-T3000type friction wear testing machine.After MoS2nano-particles with stronger surface activity were added to the electroless platesolution, the solution will easily decompose and lose efficacy because of Ni-P atomic chemicalsedimentation on the surface of MoS2nano-particles. So, electroless Ni-Mo-P-MoS2composite plating wasprepared by optimizing additive amount of MoS2nano-particles in the plating solution, pH value of theplating solution, addition amount of cationic surfactant FC4and nonionic surfactant silicane560, whichwere picked out from dozens of miscellaneous surfactant by experiment. On this basis, the effect of volumefraction of MoS2in the plating on friction coefficient and wear rate of the plating were investigated. It is found that the friction coefficient of the composite plating decreases with increase of the volume fraction ofMoS2nano-particles, and wear rate has a minimum value when the volume fraction increases. In the end,the optimal volume fraction of MoS2nano-particles in the composite plating was found.Relative to Ni-Mo-P-MoS2composite plating, electroless Ni-Mo-P-Si3N4composite plating waseasily prepared. On the basis of optimizing process parameters, the effect of volume fraction of Si3N4nano-particles in the composite plating on friction and wear property of the composite plating were focusedresearch. The result shown that the friction coefficient of the composite has a maximum value and wear ratemonotonously decreases with increase of volume fraction of Si3N4nano-particles in the composite plating.The influence of volume fraction of MoS2nano-particles on friction coefficient and wear rate ofNi-Mo-P-MoS2composite plating is different with that of Ni-Mo-P-Si3N4composite plating, whichprimary cause is that MoS2nano-particles belong to soft nature and possess with good lubricating property,but Si3N4nano-particles belong to hard particles and possess with more remarkable abrasion resistance thanthe lubricating property. If MoS2nano-particles were added into Ni-Mo-P plating with Si3N4nano-particles,wear-resistant property of Ni-Mo-P-MoS2-Si3N4composite coating would be sharply improved because oftheir synergistic effect. So an orthogonal experiment with friction coefficient and wear rate as index in2factor and3levels was designed, Ni-Mo-P-MoS2-Si3N4composite coating with different volume fractionwere prepared by changing addition amount of MoS2nano-particles and Si3N4nano-particles. And frictioncoefficient and wear rate of the composite platings were tested using MS-T3000type friction wear testingmachine, the results shown that Ni-Mo-P-MoS2-Si3N4composite coating possesses both the smallestfriction coefficient and wear rate when additive amount of MoS2nano-particles and Si3N4nano-particles isrespectively6.25g/L and3.75g/L.In order to testing friction and wear property of Ni-Mo-P coating, Ni-Mo-P-MoS2compositecoating, Ni-Mo-P-Si3N4composite coating and Ni-Mo-P-MoS2-Si3N4composite coating under thecondition of same machining of metals, they were respectively plated on high-speed steel drills withdiameter of φ6mm, these coating drills were used to cut the duralumin alloy specimens like the high-speedsteel drill with no coating for the tools life. Tool life of the high-speed steel drill with Ni-Mo-P-MoS2-Si3N4composite coating was obviously improved. In conclusion, electroless Ni-Mo-P-MoS2-Si3N4composite plating possesses both abrasionresistance of hard coating and antifriction performance of soft coating except low processing cost. It isbelieved that the high-speed steel tool with electroless composite plating will be widely used withlucubrating in addition of suitable nano-particles, optimization of structure of the composite plating,selection of suitable work material, and so on.