Improved wear properties of GCr15 steel balls by fabricating a surface Ti diffusion layer using mechanical alloying and NH3·H2O treatment

Abstract

This work used mechanical alloying combined with NH3·H2O treatment to strengthen GCr15 steel balls. First, GCr15 steel balls with a Ti coating were fabricated by mechanical alloy considering two structures of jars: one is the ordinary jar and the second is self-made special jar (SMA). Then, the deposited Ti coatings were removed by dropping NH3·H2O during the ball milling process. Surprisingly, a Ti diffusion layer is obtained on the surface of GCr15 steel balls. In particular, the Ti diffusion layers in the samples processed by self-made special jars show a thickness of approximately 3.2 μm. Mechanical Properties, such as grain, dislocation, microhardness, and friction coefficient of the processed samples, were investigated. Results show that a hardening layer of approximately 120 μm is formed on the samples processed by self-made special jars, which increased by 129% than that of samples processed by ordinary jar. A microhardness as high as 895 HV is also realized on sample surface, where obvious grain refinement and larger dislocation density were observed. The possible working mechanism was discussed. This study demonstrated that the proposed method could significantly improve the fatigue life of some mechanical components, especially for steel balls.

Keywords

• GCr15 steel ball
• Mechanical alloy
• Ti coating
• Hardening layer
• Microhardness