Ni/CrAl Composite Coatings Produced By Particle Electro-Codeposition

Nowadays MCrAlY coatings are mainly made by EB-PVD, LPPS or VPS in production field. But those equipments and constructions are expensive. Ni/CrAl composite coatings have been studied by low-cost particle electro codeposition.And the properties of the CrAl alloy powder have been explored. The effects of different milling time in a planetary ball mill on the powder size,the effects of different surface addition agent on wetting properties and the dispersity of the CrAl powder in solutions have been explored. And design a relatively simple device in order to analysis the dispersity of the CrAl alloy powder in solution. The mechanism of codeposition of Ni and CrAl particles and the effects of different technological parameters on the CrAl particle embedding in the coatings have been studied. And the deposition mechanism and corrosion behavior of the coatings have been studied by electrochemical workstations.The main results are as follows:1. The experimental results show that relationship between the particle size distribution of diameter and center milling time is d50 =34.61-22.90lglg(T/hour). the mechanical milling process parameters520round per minute and commutation per half hour.2. The contact angle between deionized water and CrAl alloy powder which increase with the temperature decrease is bigger than it between anhydrous alcohol and CrAl alloy powder which increase with the temperature increase at the same tenmpetature. but anhydrous alcohol is better. CrAl particles can adsorb some ions in solution. When the solution pH<7,it can adsorb positive ions especially pH value is about4. When the solution pH>7,it can adsorb negative ions ions especially pH value is about11. but solution pH=7,it can adsorb little ions ions.3. The influence of technological conditions parameters, such as stirring intensity, pH value, current density and temperature,on the content of CrAl particles in the composite coating were studied elementally.The resalts showed that the CrAl particles in coatings firstly increased and then decreased,The content of CrAl particles decreased obviously with pH increase,else changed a little the temperature increase, but could increase with the increase of current density or with decrease pH The optimum technological parameters:current density2.5-4.5A/dm2, pH=4-4.5temperature30℃.4. According to the properties of CrAl powder and the influence of different electro process parameters on the content of CrAl particles in the composite coating. Analysis shows that among the weak adsorption of composite particle is very important5. The oxidation kinetic curves of Ni/CrAl coatings at900℃in the air.The results show that oxidation mass gain of Ni/CrAl coating in the base of T91steel increase obviously less than Ni/CrAl coating that in the base ot A3steel. Afrer48hour oxidation at900℃, Through EDS test,found that Oxidation film is mainly A12O3and little iron...