2015 Volume 60 Issue 1 Pages 75-83
Experiments have been carried out to clarify the roles of matrix and dispersed NbC particles on the reinforcement of tool surface. It was at the end of the last century that outstanding performance in hot metal rolling was reported of the surface layer of tool reinforced with coarse NbC particles by Plasma-Transferred-Arc (PTA) welding but little has been investigated on the roles of matrix and optimum dispersion of NbC particles. In the present work specimens manufactured by PTA welding using NbC particles with different sizes and different fractions were subjected to hot sliding test against medium carbon steel in order to investigate the roles of matrix and the NbC particles held in the matrix. The result showed that the matrix is reinforced as soon as a small amount of NbC is injected into the welded layer and keeps the constant strength regardless of the increase in the fraction of NbC particles. With the increase in the fraction of NbC particles in the welded layer the performance of the surface increases linearly. In the previous use of coarse NbC powder was recommended but present result showed that the effect does not depend upon the size of NbC powder to be PTA-welded.
