Abstract
The chemical vapor deposition of diamond film on steel substrate remains with main drawbacks demanding a proper solution. Some proposed interlayers tackled with the high carbon diffusivity into steel and with the graphitic sp2 bonds catalyzed by transition metal. However, the large mismatch of the coefficient of thermal expansion between steel and diamond produces cracked and delaminated diamond films. Thermodiffused vanadium carbide (TDVC) interlayer for straight CVD diamond deposition on steel, showed disruptive results; nevertheless, the coating thickening is limited to substrate with high carbon content and low alloy steel. This work introduces the use of laser cladding (LC) to form an intermediate layer of vanadium carbide (VC) from V4C3 powder. The LC process has a short cycle time and a high VC growth rate (5.6 μm/min). Comparing with TDVC, it represents a reduction of approximately 26 times in the process cycle time. We used AISI D6 steel as substrate and overlapped VC layers to raise the coat thickness up to 25 μm. The layers showed good adherence, low porosity, and the formation of V8C7 phase. Diamond films 2.8 μm thick were deposited by hot filament chemical vapor deposition (HFCVD) at 700 °C. The Raman spectroscopy of the diamond film on four overlapped VC layers (25 μm thick) showed a compressive residual stress of 2.7 GPa. The residual stress reduction was 1.8 GPa, when compared with the 7 μm thick single cladded VC layer.
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