Abstract
Chromium carbide films with different phase contents were deposited at 126±26°C by industrial high rate reactive magnetron sputtering, using both direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS). Film structure and properties were studied by SEM, XRD, TEM, XPS, NRA, Raman spectroscopy, nanoindentation, unlubricated reciprocating sliding experiments, and a laboratory setup to measure electrical contact resistance. The films consisted of amorphous a-CrCy, a nanocrystalline minority phase of metastable cubic nc-CrCx, and a hydrogenated graphite-like amorphous carbon matrix (a-C:H). The DCMS and HiPIMS processes yielded films with similar phase contents and microstructures, as well as similar functional properties. Low elastic modulus, down to 66GPa, indicated good wear properties via a hardness/elastic modulus (H/E) ratio of 0.087. Unlubricated steady-state friction coefficients down to 0.13 were obtained for films with 69 at.% carbon, while the electrical contact resistance could be reduced by two orders of magnitude by addition of a-C:H phase to purely carbidic films. The present films are promising candidates for sliding electrical contact applications.
Highlights
Sliding electrical contacts play an important part in everyday life
The aim of this study is to investigate the structural, mechanical, tribological, and electrical contact properties of Cr–C films deposited by high rate reactive magnetron sputtering at low substrate temperature
nuclear reaction analysis (NRA) was only performed for one direct current magnetron sputtering (DCMS) and one high power impulse magnetron sputtering (HiPIMS) sample, both with a C/Cr ratio of about 1.3
Summary
Sliding electrical contacts play an important part in everyday life. Most materials used today are expensive noble metals or alloys, like Au, Pd, and Au–Co, which are applied as thin films on a conductive substrate. More cost-effective alternatives are base metals and alloys, such as Ti and stainless steel, but they more form high resistance surface oxides [1], requiring high contact forces to break through. Such forces cause severe wear and are unsuitable in e.g. consumer electronics. This can be improved by using soft metals, such as Ag, but they will exhibit severe wear even at low contact force [2], leading to reduced reliability and shortened product life. There is a driving force to design new films with lower cost and improved material properties
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