Influence of alloying elements and heat treatment on impact toughness of chromium steel surface deposits

Abstract

By means of Charpy impact tests, the impact toughness of chromium steels (nominally, 5% and 14% chromium) has been evaluated after the surfacing process and postheating at 350, 450 and 550 ° C. It has been found that impact toughness is primarily affected by the ratio between the nickel and chromium contents of the filler metals. The amount of energy required for impact fracture increases as the nickel to chromium ratio increases from 0.01 to 0.29. A metallographic analysis has shown that the nickel: chromium parameter affects the impact toughness, in that a different microstructure is obtained as this ratio varies. A marked susceptibility to temper embrittlement has been noticed for all types of filler metals examined. All materials are embrittled by postheating at 450 ° C; for some of them, temper embrittlement also occurs at postheating temperatures of 550 ° C. A decrease in toughness results in a larger number of brittle-fracture regions on the impact fracture surfaces. The brittle regions were observed to proceed primarily by a cleavage rupture mechanism.