Abstract
Carbide dispersed overlay weld alloys with the Ni–Cr–Fe matrix phase containing various amounts of NbC particles were prepared by a plasma powder welding process. Effects of the dispersion of NbC particles on wear characteristics of the alloys were investigated at sliding speeds of 0.12 to 4.39 m/s under the unlubricated condition, using Ogoshi wear tester.
The wear resistance of the alloys containing NbC particles less than 10 vol% was not remarkably improved. But it was found that the wear rate of the alloys with NbC contents more than 25 vol% was about 1⁄10∼1⁄100 times that of the NbC-free alloys and the wear loss of counter material was also very small. Especially the wear rate of the alloy with 30 vol% NbC was smaller than that of Stellite No. 6 alloy at any sliding speeds in the range of measurement.
It is considered that these excellent characteristics of wear resistance of the alloys were due to the following phenomena caused by dipersed NbC particles. Thus, at the high sliding speed (above 3.53 m/s) the coefficient of friction could be decreased with the result that the unmelted NbC particles became the true contact surface for counter material. On the other hand, at the intermidiate and low sliding speed (below 3.53 m/s) the unmelted NbC particles prevented the plastic flow of the matrix phase and the adhesion could be depressed by fine NbC powder made from the pulverized unmelted NbC particles.
