Hot filament chemical vapour deposition and wear resistance of diamond films on WC-Co substrates coated using PVD-arc deposition technique

Ferramentas diamantadas para usinagem de madeira

“…Este tipo de problema em geral é solucionado de duas formas: remoção do Co por ataque químico ou deposição de intercamadas de metais refratários na superfície do substrato [6,11,22,23,44,45]. …”

On the use of CrN/Cr and CrN interlayers in hot filament chemical vapour deposition (HF-CVD) of diamond films onto WC-Co substrates

“…Details of the experimental apparatus are elsewhere reported [28]. Here, it is worth remarking that the employed experimental apparatus consists of: i) a fluidization column, 1.2 m long and 2.5 mm thick, made from AISI 304 stainless steel and equipped with glass portholes for inspection; ii) a rotary screw compressor Quincy model QGB 15 maximum powder 15 kW, flow rate 0-130 m 3 /h, pressure ranging 0-10 bar used to feed purified air lacking in moisture and oil to the fluidized bed unit; iii) flowmeters, pressure probes, hygrometers and thermocouples to monitor the process and ensure the stability of the fluidization regime.…”

“…The impacts also generated small diamond debris, which were in part retained inside the ductile Cr-layer (i.e., embedding phenomenon [28]), thus providing anchors for the following CVD diamond coating. This way, a significant improvement of the adhesion between the diamond film and the underlying layers was promoted by FBP, whereas unpeened CrN/Cr interlayer onto WC-Co substrate led to the almost spontaneous delamination of the diamond film after CVD.…”

“…More recently, new procedures based on the use of interlayers and/or mechanical pre-treatments of the WC-Co substrates have been proposed to improve the adhesion between WC-Co and CVD diamond [28][29][30]: i) the use of PVD-arc CrN coatings as effective interlayers [28]; ii) the micro-roughening of the WC-Co surface morphology by peening at moderate pressure with a fluidized bed of brittle diamond powders joined with the chemical dissolution of surface Co [29]; iii) the microroughening of CrN/Cr coated WC-Co substrates at moderate pressure with sand blasting equipment, whereas unpeened CrN/ Cr interlayers exhibited inadequate adhesion levels of the superimposed diamond films [30]. Nonetheless, comparative evaluations among the latest pre-treatments used to improve the adhesion of diamond coatings onto WC-Co substrates do still miss.…”

“…The proposed pre-treatment was compared with the use of unpeened CrN/Cr interlayer, as well as with the wellestablished two-step chemical etching with Murakami's reagent and Caro's acid [26] and the effective CrN interlayer deposited by PVD-arc technique [28].…”