Deposition and characterization of plasma sprayed NiTi powder on stainless steel and graphite substrate

The surface behavior of the NiTi coating has been studied by composition analysis, microstructure, and interface diffusion. The shape memory effect was investigated by thermal recovery of the indented surface at various loads. Near the theoretical density (99.3%), high Vickers hardness 244-310 HV, was measured by applying various loads of 1961-98 mN for NiTi samples separated from graphite substrate. However, samples prepared from stainless steel substrate display more homogenous hardness at various loads from 214 to 238 HV with applied load from 98 to 490 mN. Phase transformation temperatures indicated that above 105 degrees C, the alloy transforms and is saturated in the austenite stage. Both samples exhibited a hysteresis effect of shape memory effect on bending mode in thermal cycles. Both samples were indented at various loads from 98 to 1961 mN load for 10 s, and residual indent points are imaged. Recovery in the depth of indent points was analyzed after heating samples above austenite finish temperature at 150 degrees C for 10 min. A maximum recovery of 77% is achieved in the sample retrieved from stainless steel substrate at 245 mN load.

Automated summary

The surface behavior of NiTi coating was studied through composition analysis, microstructure, and interface diffusion. The shape memory effect was investigated by thermal recovery of the indented surface at different loads. Samples from graphite substrate showed high Vickers hardness near theoretical density and varied with different loads, while samples from stainless steel substrate displayed more homogeneous hardness at various loads. Both samples exhibited a hysteresis effect of shape memory effect on bending mode in thermal cycles. Recovery in the depth of indent points was analyzed after heating samples above austenite finish temperature, with a maximum recovery of 77%.