Cobalt substitution in PCD cutting tool materials

Transcription

1 Cobalt substitution in PCD cutting tool materials Piotr Klimczyk 1, Lucyna Jaworska 1, Magdalena Szutkowska 1, Sławomir Cygan 1, Maciej Sitarz 2 1 Institute of Advanced Manufacturing Technology, Poland 2 AGH University of Science and Technology, Faculty of Materials Science and Ceramics, Poland

2 Introduction material properties Reliable material for cutting inserts high: hardness, wear resistance, flexural strength, fracture toughness, thermal stability, thermal shock resistance, thermal conductivity, chemical stability, low: coefficient of thermal expansion, coefficient of friction.

3 Introduction diamond, a metastable allotrope of carbon Diamond has the highest hardness and thermal conductivity of any bulk material The oxidation process occurs during heat treatment of diamond in oxygen at elevated temperatures

4 Introduction PCD materials Polycrystalline diamond PCD is a two phase product in which the diamond crystals are sintered together in the presence of metal catalyst phase Cobalt belongs to the iron group of materials, which are known to be good solvents/catalysts for diamond synthesis and also for the binder phase during the diamond powder sintering process. Unfortunately, cobalt belongs also to the group of critical raw materials.

5 Introduction PCD materials Sintered polycrystalline diamond compacts (PCD) are widely used for: cutting tools wire drawing dies and rock drill bits sintered compact cutting brazing finishing final product

6 The aim diamond based materials with high thermal resistance and without CRM Cobalt promotes graphitisation of diamond and decreases thermal stability of sintered PCD parts (e.g. cutting tools) One of the possibilities to increase the thermal resistance of PCD materials is to reduce the cobalt bonding phase content Typical PCD cutting tool material PCD + Co (12-18%) working layer WC (~90%) + Co (~10%) substrate layer CRM (WC, Co) substitution Innovative PCD composite AMBITION: down to 0% WC, 0% Co) no substrate layer necessary

7 Experimental details samples preparation diamond + 10% TiB 2 diamond + 5% TiB 2 + 2% Co Starting powders diamond (Element Six, Micron+MDA, 3-6 µm,) titanium diboride (American Elements, <100 nm ) cobalt (ABCR, µm) Preparation of material for sintering mixing: Planetary mill PULVERISETTE 6, WC grinding balls φ 5 mm, acetone, 200 rpm / 2h, drying, compaction: manual hydraulic press, ~200 MPa, discs φ 15 x 5mm

8 Experimental details HPHT sintering High pressure hydraulic press equipped with Bridgman s type toroidal anvils pressure up to ~8 GPa, temperature up to ~2400 C, duration of typical sintering process ~1 min

9 Experimental details HPHT sintering Sintering batch assemble 1 ceramic gasket (outside part) 2 ceramic gasket (inside part) 3 ceramic disc 4 molybdenum disc 5 sample 6 graphite disc 7 graphite tube 8 thermocouple (only for T-calibration)

10 Experimental details HPHT sintering Pressure distribution in the sample during plastic deformation of gasket in Bridgman's anvils system

11 P [kw] R International Days in Critical Raw Materials Experimental details HPHT sintering Sintering process takes only one minute!!! 5 5 P (Power of heating) R (Resistance) T [s]

12 Experimental details HPHT sintering Sample in the gasket before sintering Sample in the gasket after sintering Sintered compacts after grinding process Sintered compact (raw sample)

13 Results microstructure Diamond TiB 2 Co composite: SEM image and X-ray maps of C, Ti and W

14 Results microstructure Diamond Co (commercial): SEM image and X-ray maps of C, Co and W

15 Results physical and mechanical properties Composition Density Hardness Young s modulus wt.% g/cm 3 GPa GPa diamond + 10% TiB ± ± ±14 diamond + 5% TiB 2 + 2% Co 4.04 ± ± ±23 diamond + 10 Co + 2 WC (commercial) 4.14 ± ± ±34

16 Investigations tribological tests Ball-On-Disc: coefficient of friction ball material: Al 2 O 3 ball diameter: mm applied load: 4 N sliding speed: 0.1 m/s radius of the sliding circle: 4 mm sliding distance: 200 m number of cycles: ~ μ F F f n F n - applied normal force (load) F f - measured friction force

17 Investigations tribological tests Friction coefficient of diamond TiB 2 composite during sliding against Al 2 O 3 ball at 25, 200, 400, 600, 700 and 800 C

18 Investigations tribological tests Friction coefficient of diamond TiB 2 Co composite during sliding against Al 2 O 3 ball at 25, 200, 400, 600, 700 and 800 C

19 Investigations tribological tests Friction coefficient of diamond Co commercial material during sliding against Al 2 O 3 ball at 25, 200, 400, 600 and 700 C

20 Investigations hardness Hardness of diamond composites as function of heat treatment temperature (air atmosphere)

21 Investigations XRD XRD pattern of diamond - TiB 2 composite after HPHT sintering and after HT tribotests

22 Conclusions Diamond with 10 wt.% of TiB 2 and diamond with 5% TiB 2 and 2% Co composites were sintered using HPHT apparatus under the pressure of 8GPa at the temperature of 2000 C. The composites were compared with PCD commercial material The composites are homogeneous their ingredients are uniformly distributed in the volume of material The friction coefficient of all materials is the lowest ( ) at lower temperatures and rise up to about at highest temperatures RT mechanical properties of diamond composites are lower in comparison with PCD commercial material Diamond composite with addition 5% TiB 2 and 2% Co is the most resistant to the hardness changes at elevated temperatures. This material maintains the high hardness value up to 800 C

23 The research activities carried out by Institute of Advanced Manufacturing Technology scientists are supported by the European Commission under the FP7 Specific Programme 'Capacities' Development of a sintering center and know-how exchange for non equilibrium sintering methods of advanced ceramic composite materials SINTERCER REGPOT EU FP7 Research Potential SINTERCER - project no duration: