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THE DEVELOPMENT OF A NEW MULTILAYER HARD MATERIAL COATING FOR HIGH SPEED STEEL CUTTING TOOLS

Objective

The aim of the project is to optimize the production of multilayer coating for HSS inserts; by using different kinds of coating materials and by a variety of different deposition processes. The scientific and technical benefits will be the development of a new multilayer hard material coating for improving the cutting performance of cutting tools. Directly compacted and sintered high-speed steel was the substate employed. The coating consists essentially of two layers: an inner Al2O3 thermal barrier coating layer (TBCL) and an outer WC wear-resistant coating layer (WRCL). The adhesion between substrate and coating should determine the presence of absence of intermediate coating layers.
Investigations were carried out to improve the cutting performance of high speed steel cutting tools and to find the optimised deposition process.
The research demonstrated the ability to produce A1203 coatings by chemical vapour deposition (CVD) technique on high speed cutting tools as well as tungsten carbon by nonreactive sputtering and plasma arc. Coatings tested result in a high increase of the useful life of the high speed steel cutting tools. A CVD reactor was developed and built to successfully operate with what seems to be the optimal technique to produce and deposit A1203 coatings.

An extensive research programme regarding the achievement of a new multilayer hard material coating for high speed steel (HSS) cutting tools was performed.
The multilayer was selected to be composed of an alumina coating, to prevent excessive heating and consequent softening of the HSS substrate, with an outer tungsten carbide (cobalt) coating to improve the cutting performance of the tools.
Both chemical vapour deposition (CVD) and physical vapour deposition (PVD) techniques and respective operating parameters were investigated in an attempt to obtain optimum values for the coatings. It was found that suitable alumina coatings could be produced on the HSS cutting inserts using the CVD technique. Tungsten carbide (cobalt) films having a good chemical, physical and mechanical properties for cutting purposes could be obtained by nonreactive sputtering PVD.
THE RESEARCH WILL FOLLOW 4 PHASES :

- COATINGS DEVELOPED BY CVD (AL2O3 TBCL ON HSS INSERTS), PVD (AL2O3 ON HSS), DC AND RF SPUTTERING (WC AND AL2O3 ON HSS).
- COATINGS EVALUATIONS USING X-RAY DIFFRACTION, HIGH MAGNIFICATION OPTICAL MICROSCOPY, MICROHARDNESS TESTING, PROFILOMETRY, SCRATCH-ADHESION TESTS, AUGER ELECTRON SPECTROSCOPY FOR CHEMICAL ANALYSIS, RUTHERFORD BACKSCATTERING, SCANNING AND TRANSMISSION ELECTRONIC MICROSCOPY.
- CUTTING TESTS WITH AL2O3 AND AL2O3/WC COATED INSERTS.
- INDUSTRIAL CUTTING TRIALS WILL BE CARRIED OUT ON THE OPTIMISED AL2O3/WC COATED INSERTS, UNDER A VARIETY OF CUTTING CONDITIONS.

SCIENTIFIC AND TECHNICAL BENEFITS WILL BE THE DEVELOPMENT OF A NEW MULTILAYER HARD MATERIAL COATING FOR HSS CUTTING TOOLS, WITH A VIEW TO OBTAIN IMPROVEMENT IN CUTTING PERFORMANCE, PARTICULARLY USEABLE CUTTING SPEED, ABOVE THOSE CURRENTLY ACHIEVABLE. DIRECTLY COMPACTED AND SINTERED M2, T15 AND T42 GRADE HSS INDEXABLE CUTTING TOOL INSERTS WILL BE THE HSS CUTTING TOOLS EMPLOYED. THE COATING WILL CONSIST OF TWO LAYERS AS AN INNER AL2O3 THERMAL BARRIER COATING LAYER (TBCL) AND AN OUTER WC WEAR RESISTANCE COATING LAYER (WRCL).

THE ECONOMIC POTENTIAL OF THE WORK WILL BE CONSIDERABLE. MOST DIRECTLY, IT WILL CONSIDERABLY EXTEND THE RANGE OF APPLICATION OF THE HSS CUTTING TOOLS AND LEAD TO IMPROVEMENT IN PRODUCTIVITY AND REDUCTIONS IN TOOLING AND MANUFACTURING COSTS. ALSO, THE STUDY OF THE EFFECT OF HSS SUBSTRATE COMPOSITION/PROPERTIES ON THE CUTTING PERFORMANCE OF COATED INSERTS COULD LEAD TO A REDUCTION IN THE CONTENT OF STRATEGIC METALS IN THE SUBSTRATE OF COATED HSS TOOLS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

FACULDADE DE CIENCIASE TECHNOLOGIA DA UNIV. DE COIMBRA
Address
Largo D. Dinish
3000 Coimbra
Portugal

Participants (5)

INNOVATIQUE
France
INSTITUTO SUPERIOR TECNICO. LISBOA
Portugal
LABORATORIO NACIONAL DE ENGENHARIA E TECNOLOGIA INDUSTRIAL
Portugal
Loughborough University of Technology
United Kingdom
Address
Ashby Road
LE11 3TU Loughborough
UNIVERSITE DE NANTES
France
Address

Nantes