Advanced Surface Coatings: a Handbook of Surface Engineering

The past decade has seen a rapid development in the range of techniques which are available to modify the surfaces of engineering components. This in tum has led to the emergence of the new field of surface engineering­ the design of a composite system (coating plus substrate) that produces a performance which cannot be achieved by either the coating or substrate alone. With this expansion comes the problem of deciding on the correct surfacing technology for a given application. Clearly, to take full advantage of the benefits which surface engineering offers, there is a need to explain, in a structured way, the basic features and interrelationships of the most recently developed coatings and treatments. Advanced Surface Coatings satisfies this need by providing a concise and authoritative state-of-the art review of surface engineering. In chapter 1 the reader is provided with an insight into the surfacing technology appropriate for a given function. Chapter 2 reviews the principles of plasma generation (a theme which is central to many of the advanced surface treatments and coatings) and forms a solid foundation for the chap­ ters which follow. Chapters 3 to 10 each discuss the general principles on which the technology is based, followed by an appreciation of specific properties and application areas for materials treated by each particular method. These chapters cover ion implantation, ion-assisted coatings, evaporation, sputtering, physical vapour deposition, chemical vapour deposi­ tion, thermal spraying, and laser treatments.

1 Introduction.- 1.1 Surface engineering: the key to optimised performance.- 1.2 The main surface engineering technologies.- 1.2.1 Traditional surface engineering processes.- 1.2.2 Advanced surface engineering processes.- 1.3 Coating structure and characterisation.- References.- 2 Use of plasmas in deposition technologies.- 2.1 Introduction.- 2.2 Processing plasmas.- 2.2.1 DC-diode plasmas.- 2.2.2 RF discharges.- 2.3 Plasmas in the presence of magnetic fields.- 2.3.1 Applications of magnetic fields to plasmas.- 2.4 Microstructure of sputter deposited films.- 2.5 Conclusions.- References.- 3 Ion implantation and ion-assisted coating.- 3.1 Introduction.- 3.2 Beam-induced processes.- 3.3 Tribological applications.- 3.4 Applications to corrosion resistance.- 3.5 Equipment.- 3.6 The economics of ion beam processing.- 3.7 Conclusions.- References.- 4 Evaporation.- 4.1 Introduction.- 4.2 Practical aspects of evaporation processes.- 4.2.1 Resistively heated sources.- 4.2.2 Inductively heated sources.- 4.2.3 Electron beam evaporation.- 4.2.4 Arc evaporation.- 4.2.5 Laser-induced evaporation.- 4.3 Coating thickness distributions and uniformity.- 4.3.1 Lateral thickness uniformity.- 4.3.2 Front to back thickness uniformity.- 4.3.3 Absolute thickness fall-off.- 4.4 Evaporation principles.- 4.4.1 Evaporation of pure metals.- 4.4.2 Evaporation of alloys and compounds.- 4.5 Further considerations in electron beam evaporation.- 4.6 Selected applications for evaporative techniques.- 4.6.1 Large-area sheet coating.- 4.6.2 Bond coats and thermal barriers.- 4.7 Conclusions.- References.- 5 Sputter deposition.- 5.1 Introduction and historical perspective.- 5.2 Basic aspects of sputtering.- 5.2.1 Interactions on the target surface.- 5.2.2 Target considerations.- 5.2.3 Process parameter effects.- 5.3 Sputtering techniques.- 5.3.1 Reactive vs non-reactive processes.- 5.3.2 Diode sputtering.- 5.3.3 RF sputtering.- 5.3.4 Triode sputtering.- 5.3.5 Magnetron sputtering.- 5.3.6 ‘Unbalanced’ magnetron sputtering.- 5.4 Plasma characteristics and ion bombardment.- 5.5 Process control.- 5.6 Applications of sputtered hard coatings.- 5.6.1 Hard coatings on cutting tools.- 5.6.2 Sputtered decorative coatings.- 5.6.3 Engineering components.- 5.7 Industrial coating systems.- 5.8 Future trends.- References.- 6 Plasma-assisted physical vapour deposition.- 6.1 Introduction.- 6.2 The DC-diode argon discharge.- 6.2.1 The negative glow.- 6.2.2 The sheath regions.- 6.2.3 The basic mechanisms.- 6.3 Bombardment of the cathode in argon discharges.- 6.3.1 Ion and neutral energy distributions.- 6.3.2 Further ionisation considerations.- 6.4 Practical ion-plating discharges.- 6.4.1 Metal species.- 6.4.2 Reactive gas.- 6.4.3 Impurities.- 6.5 Practical considerations and system details.- 6.5.1 Commercial PAPVD systems.- 6.5.2 Coating variability.- 6.5.3 Process control.- 6.5.4 Adhesion.- 6.5.5 Other process factors.- 6.6 Applications and case studies.- 6.6.1 Industrial applications of PAPVD coatings.- 6.6.2 PAPVD vs CVD coatings in metal-cutting applications.- 6.6.3 Other applications.- 6.7 Conclusions.- References.- 7 Thermally activated chemical vapour deposition.- 7.1 Introduction.- 7.2 Principles of CVD.- 7.3 The CVD system.- 7.3.1 Gas-dispensing system.- 7.4 CVD reactors.- 7.4.1 Exhaust system.- 7.5 Design of a CVD process.- 7.5.1 Thermodynamics.- 7.5.2 Selection of precursors.- 7.6 Adhesion.- 7.6.1 Substrate.- 7.6.2 Gas flow dynamics.- 7.7 Rate-limiting steps.- 7.8 Nucleation.- 7.9 Deposition mechanisms.- 7.10 Morphology and microstructure.- 7.11 Applications of the CVD technique.- 7.12 Summary and concluding remarks.- References.- 8 Plasma-assisted chemical vapour deposition.- 8.1 Introduction.- 8.2 Discharge chemistry and physics.- 8.2.1 Basic processes occurring in a glow discharge plasma.- 8.2.2 Kinetic and thermodynamic factors.- 8.2.3 Plasma―surface interactions.- 8.3 PACVD equipment requirements.- 8.4 Applications of PACVD.- 8.4.1 Wear-resistance coatings.- 8.4.2 Thermochemical processing.- 8.4.3 Deposition of mixtures and multilayer structures.- 8.5 Summary 215.- References.- 9 Thermal spraying.- 9.1 Introduction.- 9.2 Thermal spraying.- 9.2.1 Wire spraying.- 9.2.2 Electric arc spraying.- 9.2.3 Powder flame spraying.- 9.2.4 High-velocity combustion processes.- 9.2.5 Arc plasma processes.- 9.2.6 Other techniques.- 9.3 Substrates and surface preparation.- 9.4 Coating properties.- 9.5 Applications.- 9.6 Summary.- References.- 10 Laser surface treatment.- 10.1 Introduction.- 10.2 Practical aspects of laser processing.- 10.2.1 Types of laser and their operation.- 10.2.2 Surface condition.- 10.2.3 One-dimensional thermal heating and cooling.- 10.3 Laser techniques.- 10.3.1 Laser surface melting.- 10.3.2 Laser surface alloying.- 10.3.3 Laser cladding.- 10.3.4 Laser chemical vapour and physical vapour deposition.- 10.4 Current and future applications of laser processing.- 10.4.1 Surface texturing.- 10.4.2 Enhanced electroplating.- 10.4.3 Non-contact bending.- 10.4.4 Thermal deformation.- 10.4.5 Magnetic domain control.- 10.4.6 Particle injection.- 10.4.7 Stereolithography.- 10.5 Conclusions.- References.- 11 Characterisation of coatings and interfaces.- 11.1 Introduction.- 11.2 Electron spectroscopies.- 11.2.1 Photoelectron spectroscopy.- 11.2.2 Auger electron spectroscopy.- 11.3 Electron microscopies.- 11.4 Ion spectrometry and microscopy.- 11.4.1 Secondary ion mass spectrometry.- 11.4.2 Rutherford backscattering.- 11.5 Photospectroscopies and microscopies.- 11.5.1 Infrared spectroscopy.- 11.5.2 Raman spectroscopy.- 11.5.3 X-ray diffraction analysis.- 11.6 Conclusions.- References.- 12 Evaluation of coatings.- 12.1 Introduction.- 12.2 Mechanical property assessment.- 12.2.1 Assessment of coating hardness.- 12.2.2 Measurement of coating adhesion.- 12.2.3 Tribological assessment of coatings.- 12.3 Summary and future developments.- References.- 13 Market perspective and future trends.- 13.1 Introduction.- 13.2 Future directions in surface engineering.- 13.2.1 Future developments in process technology.- 13.2.2 Developments in process understanding.- 13.2.3 Design-related factors.- 13.3 New materials and future markets for surface engineering.- 13.3.1 Composite materials.- 13.3.2 High-temperature superconducting ceramics.- 13.3.3 Diamond and DLC films.- 13.3.4 Business opportunities.- References.