Preparation And Properties Of Ni Based And Fe Based Clad Coating Using Ultrasonic Frequency Induction Cladding

Preparing coating with metallurgically bonding, excellent wear and corrosion resistance is one of the most attractive aspect in surface engineering. In this paper, ultrasonic frequency inductive cladding technique was used to prepare low cost Fe based and Ni based clad coatings. In addition, the coating preparing technique with the aim of metallurgically bonding, anti-wear and corrosion coating was studied as well. Systematically investigations concerning the following scientific questions were carried out.1. The formation and influence factors associated with the hard reinforced phase composite Fe based and Ni based clad coating.2. Microstructure and phase constituents impacted on the wear and corrosion resistance of the composite clad coating.3. The relationship between the wear resistance impacted on the transformation concerning the crystalline to amorphous transition, amorphous content of the coating in the friction process.FeCrNiCoMo, FeCrBSi, FeCrBMo alloy powders of Txxx alloys and NiCrBSi (Ni60A) alloy powders with excellent corrosion resistance as nature were selected to prepare Ni based and Fe based coatings by self-assembly ultrasonic frequency induction cladding system. The clad coatings with excellent anti-wear and corrosion resistance were metallurgically bonding to the substrate with low porosity, low dissolution rate. The experimental results showed that the porosity rate increased with the increasing working current and interaction time, the interface of coating and substrate showed ferrous metallurgy bonding and incomplete metallurgically bonding. Moreover, with the rising working current and interaction time, the porosity deduced while the dissolution rate increasing gradually, the inter-diffusion rate of varied elements from the interface of coating/substrate depended on the molten pool temperature.Ni based and Fe based coatings had a superior high density with non-equilibirum solidification structure. The microstructure of the interdiffusion zone had been shown to be epitaxial commencing with a very thin layer of planar front growth, which was ascribed to the high temperature gradient and low solidification rate at the molten pool. The bottom area of the coating was in the term of the dentritic structure. The difference of the microstructure and varied phases in the Ni and Fe based coatings mainly ascribed to the difference from the molten temperature and varied constituents. Meanwhile, pure crystalline structure of the as-clad Fe based coating was detected. The solidification sequence of the Ni and Fe based coatings could be speculated as followed, respectively:Lâ†'(γ+L)+CrB+Cr7C3â†'y+CrB+Cr7C3+γ-Ni/Ni3Si, Lâ†'(a/γ+L)+(Cr,Fe)2Bâ†'α/γ+(Cr,Fe)2B+(a/y)/(Cr,Fe)2B.Ni based and Fe based coatings displayed excellent wear resistance under dry sliding condition. Ni based and Fe based coatings microhardness presented graded distribution and raised from the bonding area to the upper side. Microhardness of the interdiffusion zone displayed over twice time higher than that of the substrate due to the eddy current and skin effect. The excellent wear resistance in room temperature of Ni based and Fe based coatings was ascribed to the dispersion strengthening of the hard phase, solid solution strengthening. With the rising of applied load, sliding time, sliding rate, the wear mechanisms of Ni based and Fe based coatings transformed from mild adhesion and abrasive wear to moderate mild adhesion and abrasive wear. The excellent high temperature wear resistance of Ni based and Fe based coatings was ascribed to the dispersion strengthening of the hard phase, solid solution strengthening as well as the protection of the self-lubricant oxide films. The wear mechanisms were adhesion, abrasive and oxidation wear. Microhardness and wear resistance of Fe based coatings were higher than that of the Ni based coating due to the higher content of hard precipitates and excellent toughness of solid solution.Ni based and Fe based composite coating showed excellent corrosion resistance. The immersion and electrochemical tests in a3.5wt.%NaCl solution showed that the corrosion mechanisms of the coatings were anodic dissolution and passive film protection. The oxide film consisted of Cr2O3, FeCr2O4, SiO2. Meanwhile, the excellent corrosion resistance of the coating was ascribed to the high density oxide film to resist the attack from the corrosion medium. In the high temperature and high pressure environment with H2S/CO2, the corrosive products of Ni based and Fe based coatings were FeS, CrS and FeS, FeCr2S4, respectively. The corrosive product deposition and high dense corrosive film enhanced the corrosion resistance of the coating with a certain high temperature. The oxidation dynamics curve of clad coatings took on para-curve. Due to the high dense oxides (Cr,Fe)2O3formed onto the clad coatings, the coatings showed good high temperature oxidation resistance.In the friction treatment, large plenty of dislocations lead to the metamorphic transformation of the crystalline-amorphous phase transition occurred within upper layer surfaces of the coatings FeCrNiCoMo and FeCrBSi. With continued friction, destabilization of the crystalline phase probably occurs when the free energy of the crystalline phase reaches to a level higher than that of the amorphous phase and consequently, thus resulting in the possibility for the formation of amorphization. The content of amorphous phase increased gradually and then tended to be stable around40%with the increment of sliding time and applied load. With the increasing solidification rate, the radius of the top dentritic phase reduced whilst the dentritic spacing decreased gradually. The austenite zone enlarged followed the high content of Ni element. The primary austenite phase showed ellipsoidal shape in high Ni element content and showed irregular shape in low content. The wear predictive mode based on the LS-SVM was proposed, the wear predictive mode displayed good results with relative small quantities of predictive samples.On the basis of the optimizing processing parameters, an efficient induction cladding method was established for the single preparation Ni based and Fe based coatings with precise controlling. The clad coatings with thickness of6,3.6mm were deposited onto the Q235steel and guide roll, respectively. Meanwhile, the exterior protective coating mainly composed of SiO2and Al2O3, leading to the transformation from mechanically bonding to metallurgically bonding concerning the as-sprayed coating after induction remelting. Hence, the coating porosity reduced to0.43%from5.74%whilst the corrosion resistance was remarkably improved2.74times in comparison to the as-sprayed coating.