17526 - Surface Treatments and Ceramic Coatings

Learning outcomes

The aim of the course is to illustrate the materials surface properties and the main surface modification techniques, in order the student is able to:

a)  select the most suitable surface treatment for a given application,

b) individuate the best surface technologies as a function of the substrate type and   functional requirements,

c)  know the main available techniques for analysis and testing of coated products.

Course contents

Surface properties of materials: chemical and mechanical interactions with the environment and countermaterials. Wet and dry corrosion of metals: Pourbaix and Evans diagrams.  Techinques of active protection. Passive protection by surface treatments and coatings. Friction and wear. Surface modifications for tribological applications.
 
Conversion treatments of metals. Structure and  properties of the phosphate concersion layers. Composition and protectiveness of the chromate films. Cr-III based and Cr-free passivations. Anodic oxidation of Al, Mg and Ti alloys. Formation, coloration and sealing of the anodic layers. Plasma electrolytic oxidation.
 
Thermochemical surface treatments of steels: carburizing, nitriding and nitro-carburizing. Strusture and properties of the reaction and diffusion layers. Boriding and diffusive metallization. Chromization and alluminizing.
 
Coating deposition by thermal spray. Microstructure of the thermally sprayed coatings. Applications of thermal spray: corrosion and wear resistant, abradable, thermal barrier and biocompatible coatings.
 
Vapor phase deposition. Conventional and innnovative CVD techniques. PVD processes: evaporation, sputtering and ion plating. Microstructure of the vapor deposited films. Ceramic thin coatings for tribological, optical and electronic applications. Ceramic films deposited by sol-gel techniques.
 
Enameling of metals. Composition and properties of porcelain enamels. Metals suitable to enameling. Enameling techinques: electrostatic and electrophoretic deposition. Firing of the enameled articles, Application fields of the porcelain enameling.   

Readings/Bibliography

Set of lectures edited by Prof.Lanzoni
1) J.R.Davis (edited by) “SURFACE EBGINEERING”   ASM International 2001
2) S.Grainger  (edited by) “ENGINEERING COATINGS”  Abington Publ. 1989
3) K.Stevens “SURFACE ENGINEERING TO COMBAT WEAR AND CORROSION”   IOM Publ. 1997

Teaching methods

Lectures are, at first, devoted to the study of the chemical and physico-mechanical properties of a material surface. Some treatments aimed to transform  the surface of a metal into a ceramic or composite layer are then illustrated. But the main part of the course in concerned with the ceramic coatings deposited by PVD, CVD, sol-gel, thermal spray and enamelling.

 

Assessment methods

The learning level will be assessed by a oral exam, with the aim  to verify the student capacity to  explain a coating property on the basis of its structure and composition, and to devise a surface treatment most suited to a given application.

 

Teaching tools

Video-projector, PC and light-board.

Office hours

See the website of Elio Lanzoni