Oxidation Of Fe-based Particles In Arc Spraying Process

The oxidation of spray particles is very common in arc spray, and it isdetrimental for coatings. Since the oxidation of spray particles, a series of researchwere carried out from material and process aspect. Fe-based alloy3Cr13with otherlight elements were selected as spray material, the influence of arc spray processparameter, Boron and Silicon on oxidation of spray particles was researched toestablish relationship. Furthermore, the effect on particles oxidation on wear behaviorand immersion corrosion of the3Cr13coating was investigated. The major results aresummarized as follows:Oxide phases are FeO, Fe3O4and FeCr2O4phase exhibit3Cr13coatings, withthe main phase are Fe-Cr solid solution. As spray distance increases, the number ofoxides and porosity increases, the splat extent of particles reduces, the number ofspherical particles increases. When3Cr13solid cored wire and3Cr13cored wire weresprayed, the coating corresponding to3Cr13solid cored wire contains identicalcomposition with the coating corresponding to3Cr13solid cored wire. The splatparticles’or in-flight particles’’dimension of3Cr13solid cored wire are more uniformcompared with3Cr13cored wire. The in-flight oxidation is the main oxidationmechanism during the total oxidation of arc spray oxidation when Fe-based coating isprepared. The number of oxides in coatings atomized by compressed N2gasdecreases compared with the coatings atomized by compressed air.The in-flight particles’ size of Cr13alloy sprayed increases by adding B or Sielement. The reason is possible that viscosity of Cr13alloy increases when B or Sielement is added, hence the size of particles atomized increases. Furthermore,particles with small size are oxidized strongly by simulated establish oxidation model.The content of oxides in the Cr13coatings adding B or Si element is less than thecontent of oxides in the Cr13coatings without any elements. The oxides reducerapidly when Cr13alloy is added into more content of B or Si. The reason that oxidesin Cr13coatings are decreased when B or Si is added is discussed. The first possiblereason is that more big particles is produced, what’s more, B or Si is more active, theprior oxidation of B or Si is prior to oxidation of Fe or Cr when Fe-based alloy addingB or Si element is sprayed. When Si is added into Cr13alloy, the dense Si-O oxidesare produced on the surface of fluid particles to prevent oxidation of metal. The influence of oxides on wear resistance or corrosion resistance is complex.The oxides or porosity increase with the spray distance, the micro-hardness ofcoatings decreases when oxides or porosity is increased. The weight loss of wearingincrease when micro-hardness of coatings drops. The abrasive mechanism is brittleflaking when large number of oxides exhibit in coating. When the oxides in coatingare little, the wear resistance of coatings depends on the splat particles. Theimmersion corrosion of Cr13coatings was carried out to investigate the influence ofoxides on corrosion resistance. The surface of coating is destroyed strongly whenspray distance is increased. The oxide is the defect in the coating, so the corrosion isstronger when more oxides exist in coating. The immersion corrosion production ofCr13coatings is oxides of Fe or Cr, and the number of immersion corrosionproduction increase with the oxides and porosities.