Research On The Preparition Of Ni-based Self-fluxing Alloy Powder And The Performance Of Anti-corruption Of The Coating Of It

Corrossion, as one of the three invalidation forms of the mechanical parts, is related to all the departments of the national economy.One new Ni-based self-fluxing alloy powder has been designed according to the experienced anti-corrossive alloys and the work that our team done before,by the way of APF. The Performance of the coatings,which were made by spraying the alloy powder by the way of oxyacetylene flame and plasma transferred arc surfacing, was studied through the quality of the coatings,electrochemical corrosion, high temperature oxidation and thermal fatigue.From the appearance of the coatings,the makeup phases,the quantity and distributing of the disfigurations,the fluctuation of the microhardness and the element diffusion of intergrated zone,we knew that,the coatings intergrated with the base metallurgically and the coating formed by plasma transferred arc surfacing was better than the one formed by oxyacetylene flame spraying.By mensurating the anodic polarization curves of the two kinds of coating and the stainless steel 1Cr18Ni9Ti within various concentrations of vitrol H₂SO₄(wt%),10% hydrochloric acid HCl, and the mixed acid (with 15% hydrochloric acid +15% vitrol H₂SO₄+10% phosphoric acid H₃PO₄+10% nitric acid HNO₃),the saturated FeCl₃ solution,the variation of the corrossion potential and current, the passive current and the puncture potential of the two kinds of coating and the stainless steel in the same electrolyte and of the same kind of coating in different kinds of electrolyte,would be obtained. The experiment results showed that the corrossion speed of the two kinds of coating firstly growed up then slowed down as the concentration of vitrol H₂SO₄ growed up,and the formation of the passivation membrane was firstly hard and then becamed more easily as so. In 10% hydrochloric acid and the FeCl3 solution,the corrossion speed of the stainless steel was the highest and the one of the plasma transferred arc surfacing coating came out the slowest .And in the mixed acid,when the potential reached 1.2V,the polariztion curve of the two kinds of coating became flat and the passivation zone didn't appeared,it showed that the coating was sable during the later stage and the corrossion speed became slower in the mixed acid. The polarization curve of the stainless steel appeared zigzag,which showed that the passivation membrane formed on it but was soonly dissovled by the acid. i.e. the membrane didn't prevent the corrossion. However,the polarization curve of the stainless steel climbed fast and the corrossion speed became higher.The way of weight-gaining was employed during the research of the performance of anti-high-temperature-oxidation at 750℃ of the two kinds of coating and the stainless steel 1Cr18Ni9Ti. The appearance of the oxide was observed by SEM and the phase constitution was analysed by XRD. And the oxidation-weight-gaining curve was drawed non-linearly. The result showed that the oxidation-weight-gaining curve of the two kinds of coating followed the parabola curve and the oxide of them was chromic oxide Cr₂O₃, which wasn't exist after a 100 hours oxidation of the stainless steel. So the two kinds of coating appeared excellent anti-oxidation performance.The thermal spraying samples with different thickness were put into the muffle furnace for the thermal fatigue test. The results showed that the anti-thermal-fatigue performance of the coating would decreased sharply when the thickness of the coating was bigger than 5mm. But the coating wouldn't fall off during the test when the thickness was less than 3mm. Cracks appeared earlier in the oxyacetylene flame spraying coating than in the plasma transferred arc surfacing coating and the quantity was more than that of plasma tansferred arc surfacing coating, the spreading speed was more quickly.