بررسي خواص سطحي پوشش هاي الكترولس تك لايه و هيبريدي نيكل-فسفر/نيكل-بور روي فولاد زنگ نزن مارتنزيتي با هدف بهينه سازي خواص تربيولوژيكي

چكيده انگليسي :

98 Investigation of the surface properties of single layer and hybrid Ni P Ni B electroless coatings on martensitic stainless steel with the aim of optimizing the tribological properties Amir Tohidi Moghadam a tohidi@ma iut ac ir 18 JAN 2015 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Seyed Mahmoud Monirvaghefi vagh mah@cc iut ac irAbstractIn this research surface properties of different types of single layer and hybrid Ni P Ni Bcoatings prepared by electroless plating were investigated with the aim of optimizing theirtribological properties Martensitic stainless steel type 410 which has received a lot of interestin petroleum and power applications was used as substrate material Acidic bath was used inorder to deposit single layer Ni P coatings including low medium and high phosphorouscoatings By varying the pH of the bath in the range of 4 3 6 7 aforementioned coatings wereformed with a thickness of 30 m To obtain a single layer Ni B coating basic bath with a pHof 13 was used and a 30 m thick coating was deposited on the substrate In order to obtainhybrid coatings surface preparation was done on substrates First substrates were immersed inelectroless Ni P bath and remained until formation of a 20 m thick coating Then they wereplunged in nickel strike bath in order to improve the adhesion of Ni B coating to theintermediate layer Finally samples were put in an electroless Ni B bath and kept until thedeposited coating reached a thickness of 10 m In order to investigate and compare thetribological properties of coatings in as deposited and heat treated conditions heat treatmentwas done on each coating for 1 hour at 400 C Evaluated surface properties includemorphology roughness hardness wear and friction coefficient which were studied usingscanning electron microscope X ray diffraction analysis optical microscope vickersmicroharness testing machine surface profilometry and pin on disc wear test machine Theresults of evaluating the morphology of Ni P coatings indicated that higher phosphorouscontent in coating results in finer morphology and lower roughness Also obtained resultsshowed the similarity between Ni B and Ni P morphologies However Ni B coating hadrelatively higher porosity content and roughness due to high deposition rate Heat treatment onelectroless Ni P and Ni B coatings lead to an increase in hardness and wear resistance and alsoa decrease in friction coefficient Therefore heat treated high phosphorus coating had thehighest hardness value about 1010 HV and wear resistance and the lowest friction coefficient about 0 44 among all heat treated and as deposited single layer Ni P coatings For singlelayer Ni B coatings heat treated coating showed the highest hardness value about 1130 HV and wear reasistance and the lowest friction coefficient 0 44 among as deposited and heattreated single layer Ni B coatings Evaluation of the morphology of hybrid coatings showedthat Ni High P Ni B hybrid coating has finer morphology and lower roughness compared toNi medium P Ni B and Ni low P Ni B Also Ni low P Ni B coating despite of the lowerhardness gradient has lower hardness and wear resistance Among as deposited and heattreated electroless hybrid coatings Ni high P Ni B coating had the highest hardness value about 1320 HV and wear resistance and the lowest friction coefficient 0 37 Weight lossresults of heat treated Ni high P Ni B electroless coating as the best hybrid coating indicatedan 85 improvement in wear resistance compared to heat treated Ni B electroless coating asthe best single layer coating So Ni high P Ni B electroless coating showed the besttribological properties among different single layer and hybrid coatings Key words Electroless coating Hybridic Ni P Ni B Wear Friction coefficient

توحيدي مقدم، امير

بررسي خواص سطحي پوشش هاي الكترولس تك لايه و هيبريدي نيكل-فسفر/نيكل-بور روي فولاد زنگ نزن مارتنزيتي با هدف بهينه سازي خواص تربيولوژيكي

سايش , ضريب اصطكاك