The prime objective of this project is to develop and evaluate advanced composite (ceramic and ceramic/metal) coatings, deposited by ionisation assisted PVD techniques specifically for tribological applications in industry. Two main PVD methods are used: reactive evaporation and magnetron sputtering. Generic research on the processes is combined with specific coating development programmes (e.g. on single, bi- and multiphase layer structures, such as Ti-B-N compounds). This is supported by a three stage assessment programme, classified as Characterization, Evaluation and Model Testing. Characterization includes determination of the basic properties of layers, including thickness, microstructure, chemical composition, preferred orientation, etc. Evaluation includes hardness, adhesion and basic tribological properties. Model tests are devised to simulate real industrial contact conditions, including metal cutting, high and low stress adhesion and abrasion.
Titanium aluminium nitride, titanium boride plus boron nitride and titanium boride plus nitrogen coatings have been developed as replacements for titanium nitride to improve wear resistance in cutting tools. Early tests using standard evaluation methods revealed that these coatings had promising characteristics. The coatings, when evaluated in model cutting tests revealed most interesting results. Firstly the deposition method can critically influence the performance of real components as a result of thickness variations and internal stress effects in the film. Secondly the behaviour of the coating differs considerably depending on the tribological contact conditions. This applies when different tests are used and even on different faces on the same tool in metal cutting. Thus titanium aluminium nitride coatings showed particularly good wear resistance on the flank face but rate face performance and nose fracture behaviour were critical to tool failure. Although the best of the titanium boride with nitrogen coatings could match exisiting titanium nitride coating performance the results were critically dependent on the deposition method and on the coating thickness. For maximum benefit it is advisable to develop specific coatings for specific applications and tribological contact conditions.
THE TWO MAIN PVD TECHNIQUES APPLIED WILL BE IONISATION ASSISTED REACTIVE EVAPORATION AND MAGNETRON SPUTTERING.
THE APPROACH ADOPTED WILL BE BY "SURFACE ENGINEERING" WHEREBY COATINGS ARE TAILORED TO HAVE SPECIFIC PROPERTIES SO AS TO MEET SPECIFIC NEEDS.
THE RESEARCH IS DIVIDED INTO 3 PHASES :
- LAYER DEVELOPMENT AND PRODUCTION; INCLUDING SINGLE, BI- AND MULTIPHASED LAYER STRUCTURES (SUCH AS HFN AND TIBN);
-BASIC PROPERTIES OF LAYERS, INCLUDING THICKNESS, MICROSTRUCTIVE, CHEMICAL COMPOSITION, HARDNESS, ADHESION, ETC.
- MODEL WEAR TESTING AND CUTTING TESTS; ABRASIVE AND ADHESIVE WEAR BEHAVIOUR, STRESS SIMULATIONS, SLICKING FRICTION TESTS UNDER LABORATORY AND INDUSTRIAL CONDITIONS.
THE DEVELOPMENT OF NEW TAILORED MULTIPHASE COATINGS WILL LEAD TO PRODUCTS HAVING SUPERIOR SURFACE PROPERTIES WITH RESPECT TO ABRASIVE AND ADHESIVE WEAR RESISTANCE AND CUTTING CAPABILITIES. FOR EXAMPLE, IT SHOULD ALLOW SURFACES OF HARD CERAMICS TO BE TOUGHENED THEREBY IMPROVING IMPACT PROPERTIES.
ECONOMIC BENEFITS WILL ACCRUE FROM THE EXTENDED TOOL LOFE PERFORMANCES, IMPROVED PRODUCTIVITY AND REDUCED "DOWN-TIME". REDUCTION OF COATING TEMPERATURES WILL ALLOW CHEAP LOW ALLOY STEELS TO BE USED WITH CONSEQUENT COST AND RESOURCE SAVINGS, THEREBY REDUCING THE EEC'S RELIANCE ON STRATEGIC MATERIALS, SUCH AS CHROMIUM AND COBALT.
Funding SchemeCSC - Cost-sharing contracts