Growth Kinetics of CoB–Co2B Layers Using the Powder-Pack Boriding Process Assisted by a Direct Current Field

Abstract

New results about the growth kinetics of CoB–Co2B layers developed at the surface of CoCrMo alloy using the powder-pack boriding process assisted by a direct current field (PBDCF) were estimated in this work. The PBDCF was conducted at temperatures of 1048 – 1148 K with different exposure times for each temperature, whereas the growth kinetics of the cobalt boride layers was modelled using a system of two differential equations. In addition, indentation properties such as hardness, Young’s modulus and residual stresses were estimated along the depth of the borided CoCrMo surface. The growth kinetics of the cobalt boride layers developed by PBDCF indicated that thicker boride layers were formed on the material’s surface which was in contact to the current field at the anode, in contrast to the surface exposed at the cathode. The kinetics of cobalt boride layers were compared with those obtained by conventional powder-pack boriding process.

Keywords

• powder-pack boriding
• direct current field
• cobalt boride layer
• growth kinetics
• depth-sensing indentation
• (2010)
• 64.10.+h
• 64.30.+t
• 68.35.fx
• 72.15.eb
• 62.20.-x