a1 The Timken Company, Canton, Ohio 44706; and Case Western Reserve University, Cleveland, Ohio 44106
a2 The Timken Company, Canton, Ohio 44706
a3 Duke University, Durham, North Carolina 27708
Hardness, elastic modulus, and stress directly influence the ability of tantalum carbide/amorphous hydrocarbon (TaC/a-C:H) thin films to enhance the wear-resistance of steel tribological component surfaces. Designed factorial experiments enabled an evaluation of the effects of acetylene flow rate (QC2H2), direct current bias voltage level (Vb), and substrate rotation rate (ωRot) during deposition on the mechanical properties of reactively sputtered TaC/a-C:H films. Significant relationships were found between compressive stress level and Vb, whereas hardness and elastic modulus were dependent primarily on Vb and secondarily on QC2H2 within the studied parameter space. It is proposed that effects of ion bombardment on the a-C:H phase during growth are responsible for property dependencies on Vb. Decreases in hardness and elastic modulus with increasing QC2H2 are attributed to increased hydrogen concentration and a concomitant decreased volume fraction of TaC crystallites in the films.
(Received December 21 2005)
(Accepted March 09 2006)
(Online publication June 2006)