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Research On Electroless Plating Of Ni-P-MoS2 Composite Coating And Its Wear Behavior

Posted on:2017-01-12Degree:MasterType:Thesis
Country:ChinaCandidate:Q Q XieFull Text:PDF
GTID:2271330503464048Subject:Materials engineering
Abstract/Summary:PDF Full Text Request
As a self-lubricating composite coating, nickel–phosphorous–molybdenum disulfide composite coating is often known. The study on the coating is mainly focus on its technique parameters and friction alleviation property. A systematical study on wear property and wear characteristics of Ni-P-MoS2 composite has important directing significances to industry application owing to the nonproficient understanding of wear resistance and mechanism hitherto. In this paper, A nickel–phosphorous–molybdenum disulfide composite coating was prepared on 45 steel substrate by electroless plating. The effect of dosage of MoS2 in bath(MoS2 content in coating) on the wear behavior of coatings were studied. In order to increase the microhardness of coatings, change the microstructure by a heat treatment. The morphologies, microstructures, wear characteristics and mirohardness of coatings were characterized by micro-means of X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and microhardness tester. The formation and function of friction layer were study. And the wear mechanism of different coatings was also discussed in contrast to 45 steel.The results shows that the matrix metal of coatings transfers from amorphous to crystalline and the microhardness increases after a heat-treatment. The microhardness presented the highest value(1040HV) after heat-treatment at 400℃, but the microhardness decreased with MoS2 additive amounts increased. Wear loss of coatings with different MoS2 additive amounts increased with load. The wear loss of the Ni–P–MoS2 composite coating obtained from bath with 1 g/L MoS2 was lower than Ni-P coating. But the composite coating obtained from bath containing excess amount of MoS2(> 2 g/L) had a rather poor wear resistance due to its high brittle property. A mechanically mixed layer(MML) with a protective effect on wear surface can be formed during friction process,which depended on the wear debris and conditions. The Ni–P–MoS2 composite coating obtained from bath with 1 g/L MoS2 has better wear resistance, which is ascribed to the integrative role of its high microhardness of coating, the lubricating effect of MoS2 and mechanically mixed layer(MML). The composite coating obtained from bath containing excess amount of MoS2(> 2 g/L) has a rather poor wear resistance due to the fact that it has low microhardness and no mechanically mixed layer(MML) can be formed during friction process for its high brittle property.The wear mechanism of different coatings transformed with the increase of load. Concerning the Ni-P coating, the wear mechanism converted low-stress abrasive wear and transfer to adhesive wear, to adhesive and mild abrasive wear, to oxidative wear, abrasive wear, plastic deformation and mild adhesive wear co-existed. The transition of mild-severe wear occurred. As for the Ni–P–MoS2 composite coating obtained from bath with 1 g/L MoS2, the wear mechanism changed from abrasive wear, transfer and delamination wear to adhesive wear and delamination wear, then to adhesive wear, abrasive wear and transfer. The transition of mild-severe-mild wear took place. With regard to the Ni–P–MoS2 composite coating obtained from bath with 2 g/L MoS2, the wear mechanism converted severe plastic deformation and mild abrasive wear to abrasive wear and mild plastic deformation, then to abrasive wear and adhesive wear, finally to oxidation wear, abrasive wear and adhesive wear. The transition of mild-severe wear come up.
Keywords/Search Tags:nickel–phosphorous, molybdenum disulfide, electroless plating, composite coating, wear, mechanism, mechanically mixed layer(MML)
PDF Full Text Request
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