Nitriding of hardfaced layers as a method of improving wear resistance of hot forging tools

The article deals with novel hybrid layers combining hard facing and nitriding to improve forging tool durability. It includes a study of the nitriding capabilities of hard facings made of typical materials used to repair key groups of hot forging tools. Tests were conducted on samples and on tools in forging processes. Tests on samples included hard facing, nitriding, microstructure, micro hardness, XRF phase analysis and abrasive wear tests. Experimental tests on forging tools included operational tests and comprehensive wear analysis by scanning, macroscopic and microscopic observations by light and scanning microscopy, and analysis of wear mechanisms. Tests on the samples confirmed the positive effect of nitriding on performance properties at room and elevated temperatures. They revealed the reduced susceptibility to nitriding of some welds and the variable composition of nitrides present on the surface of the samples, which has a key effect on the observed wear mechanisms in the ball-on-disc test. Operational tests showed the effect of improved durability, which is greatest for the DO*15 (Fe–Cr– Mo–W)+nitriding layer which is due to the increased hardness of the weld itself and the increased susceptibility to nitriding.