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Corrosion properties of titanium based hard coatings on steel
Author(s) -
Hirschfeld M. K.,
Pfohl C.,
Rie K. T.,
Schultze J. W.
Publication year - 1998
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.19980290907
Subject(s) - materials science , corrosion , coating , titanium , tin , metallurgy , titanium nitride , tempering , microstructure , deposition (geology) , conversion coating , composite material , nitride , layer (electronics) , paleontology , sediment , biology
Titanium nitride TiN, titanium boronitride Ti(B,N) and titanium carbonitride Ti(C,N) coatings were deposited by PA‐CVD on tempering and stainless steel substrates. The deposition process can be supervised by OES. The coatings were characterized XRD, SEM and WDS as well as hardness, adhesion and friction tests. Electrochemical impedance measurements and cyclic voltammetry in praxis relevant media were carried out. Mechanical and corrosion properties of the coatings can be controlled by the PA‐CVD process parameters. The incorporation of chlorine in the coating can be varied by the process parameters with TiCl 4 or completely avoided using metallo‐organic precursors. No influence of the chlorine content on the corrosion behavior was observed. Even coatings with extremely high chlorine content still exhibit an excellent corrosion resistance. Thus, the microstructure of the coating is the key to the corrosion properties of hard coatings on steel. A new micro electrochemical scanning droplet technique with a lateral resolution of 150 μm allows the investigation of TiN‐coated substrates of complex geometry. The PA‐CVD technique permits the deposition of dense and pinhole free coatings. On structures with simulated aspect ratios less than 3, a dense protective coating is proved. However, if the formation of micro pores is not suppressed by the optimal choice of deposition parameters, low‐alloyed steel substrates corrode through pores, causing a detachment of the coating. On layers deposited on stainless steel, no sign of substrate corrosion could be detected. A model for the corrosion mechanism is given in Fig. 17.