Sliding wear properties of 60NiTi as compared to 440C steel

What is it about?

60NiTi has a similar Rockwell C hardness and a lower elastic modulus, about half that of 440C steel. Moreover, both 60NiTi and 440C steel show similar high tensile strengths. Consequently based on conventional wear theories such as Archard’s theory or Oberle’s model that take account of macroscopic mechanical properties (macro hardness and elastic modulus), 60NiTi is expected to show similar or even superior sliding wear properties than 440C steel. However, results of the current studies, comparing the sliding wear properties of 60NiTi and 440C steel plates mating with WC balls, show that 60NiTi displays a very much inferior wear resistance than 440C steel under unlubricated conditions. In particular, 60NiTi exhibited ~42, ~133 and ~121 times higher specific wear rates than 440C steel under 2, 5 and 10N loads, respectively. On the other hand, under good lubricated conditions, 60NiTi was able to form a perfect lubricating film causing a significant drop in the CoF values. Under such conditions, 60NiTi showed a similar behavior to 440C steel and did not wear. However, the occurrence of this wear-free condition was limited to reduced loads and good lubricated conditions. The reasons behind these observations and the differences in the sliding wear behavior of 60NiTi and 440C steel are investigated in this article. In addition, using a stress model and experimentation, the precise conditions under which 60NiTi shows a proper sliding behavior for sliding applications are defined.

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Why is it important?

This research, in addition to introducing 60NiTi as a material having the potential for use in load bearing applications other than rolling, will help the engineering community to properly apply 60NiTi in situations where materials slide over each other.

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