The Research On Micro-structure And Wear Resistance Of Nickel-based Coatings Reinforced By Carbides

Wear,fracture and corrosion are primary failure mode in machine parts,and wear accounted for 3/5~4/5.According to incomplete statistics,the losses caused by wear are very serious in our country every year,using tribology knowledge can save more than 100 billion.It is of great significance for the social economic benefits and engineering applications to develop wear-resistant materials or the wear-resistant layer on the surface of the machine parts,to improve the wear resistance of the material and to prolong its service life.In this paper,nickel-based alloy Ni60 A was chose as base powder,and deposited on Q235 A steel by transferred plasma arc spray welding technology.Then the properties of the surface was characterized by micro-structure analysis,hardness analysis,X-ray diffraction analysis,SEM analysis,EDAX analysis,dry friction-wear analysis and dry abrasive wear analysis.In order to strengthen the coating further,the second phase strengthen theory was carried out,by adding different types and different contents of carbides powder into it,that were NbC,VC and WC powders,and the influence of carbides on the nickel-based coating was studied by these analysis mentioned above.The results show that,the coating of Ni60 A has shaped up well.The matrix of Ni60 A was ?-Ni,which contained lots of Cr,Fe atoms.The coating layer contained the hexagon carbides M7C3 significantly,which were(Cr,Fe)7C3 carbides after been proved by X-ray diffraction analysis and EDAX analysis.These kinds of carbides show high hardness and can effectively resist the wear of materials.After been tested by high speed reciprocating friction wear tester,the coating of Ni60 A shows lots of scratches combining with plows,the wear loss amount was 0.0217mm3;and after abrasive wear test,the weight loss was 0.1046 g.The addition of NbC in Ni60 A,the grain size of the coatings have refined,in the coatings,diamond-shaped or irregular polygon of NbC dissolved/embedded in the matrix or epitaxial solidified with carbides,the micro-hardness has improved with the increasing of NbC.In friction and wear test,the friction coefficient has decreased,the amount of wear loss can decrease 23.96% with the best anti-wear properties(the content of NbC was 10%),the layer exists obvious plastic flow,for the adhesive wear;compared with Ni60 A,the abrasive wear performance can be 1.68 times after the addition of 10% NbC.The addition of VC,VC has been broken up into V and C atoms,parts of V atoms dissolved into the matrix,so around the matrix,the C level has raised up.This phenomenon benefits the nucleation and growth of hard phase,lots of refined hard phase gathered around the matrix and protected the matrix.In friction wear test,the friction coefficient has obviously decreased,the major wear is fatigue.In abrasive wear test,5%VC addition showed the best wear performance,the weight loss was 0.0950 g,only 1.1 times to the Ni60 A.The addition of WC in Ni60 A,the layer shows the severe sink phenomenon.With the content of WC increasing,parts of melted WC evolved from lamellar-like into block-like and embedded into the matrix,improving the properties of coatings.The micro-hardness improved with the addition content of WC,due to the sink phenomenon,the hardness next to the fusion line higher than other parts.The friction coefficient has decreased,the amount of friction wear loss decreased with the addition content of WC,the wear morphology has obviously scratches and plows,the wear characteristic is mainly abrasive wear.And all abrasive wear loss were lower than pure Ni60 A coating,the maximum can be raised to 2.49times(10%WC).Once the content of WC was too high,the coating emerged the cracks in macroscopic,and the abrasive weight loss has improved slightly,which will influence the use of the coatings.