Surface hardening of age-hardenable Cu–Ti alloy by plasma carburization

• Published in: Surface & coatings technology Vol. 283; pp. 262 - 267
• Main Authors: Semboshi, S., Iwase, Akihiro, Takasugi, T.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-12-2015
• Subjects: Age hardening; Carburizing; COPPER ALLOYS (40 TO 99.3 CU); Copper base alloys; COPPER TITANIUM ALLOYS; Cu–Ti alloy; Formations; HARDENABILITY; HARDNESS; Plasma carburization; PLASMAS; Surface hardening; TiC; Titanium base alloys; Titanium carbide; Wear; WEAR MECHANISMS; Wear toughness; BF; Surface hardening; Wear toughness; fcc; SAED; Hardness; GIXD; TiC; Plasma carburization; Cu–Ti alloy; EDS; TEM; DC
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2015.11.003

Plasma carburization was performed on specimens of a commercially used age-hardenable Cu–Ti alloy, in order to improve its surface hardness and wear toughness. Specimens of a Cu–4mol% Ti alloy were carburized in a methane gas glow discharge plasma at temperatures of 1073K and 1123K for 6h. The plasma-carburization treatment resulted in the formation of two layers of crystalline compounds on the surfaces of the Cu–4mol% Ti alloy specimens: (i) a TiC top layer containing 11at.% oxygen and (ii) a Cu3Ti3O sublayer. The thicknesses of the TiC and Cu3Ti3O layers were approximately 100nm and 900nm, respectively, in the case of the specimen plasma-carburized at 1073K. This led to significant improvements in the surface hardness and wear toughness of the specimen. It was interesting to note that the presence of a carbon-friendly alloying element (Ti) at a concentration of only 4mol% resulted in the formation of a hard TiC layer, leading to the surface hardening of the Cu-based alloy. Furthermore, plasma carburization at a higher temperature of 1123K resulted in the formation of thicker layers of hard TiC and Cu3Ti3O, causing a greater degree of surface hardening. Thus, it was demonstrated that plasma carburization is highly suitable for the surface modification of age-hardenable Cu–Ti dilute alloys.
•Specimens of a commercially used age-hardenable Cu–Ti alloy are plasma carburized.•The resulting changes in their surface hardness and wear toughness are determined.•A TiC surface layer and a Cu3Ti3O sublayer are formed after carburization.•These layers improve the surface hardness and wear toughness significantly.•The thicknesses of the layers increase with the carburization temperature.