HYDROGEN EMBRITTLEMENT OF HIGH DUCTILITY CAST IRONS 
W.L. Guesser, L.C. Guedes, I. Baumer, A. Pieske 
Industria de Fundigao Tupy Ltda — Joinville - SC — Brazil 
Abstract 
THE EFFECT OF HYDROGEN ON THE MECHANICAL PROPERTIES AND FRACTURE BEHAVIOR OF FERRI~- 
TIC MALLEABLE AND DUCTILE IRONS WERE INVESTIGATED. 
IT WAS VERIFIED. THAT HYDROGEN CAUSES A LOSS IN DUCTILITY AND A CHANGE IN THE FRACTU- 
RE MODE, FROM DIMPLES TO CLEAVAGE. THE CLEAVAGE FACETS INDUCED RY THE HYDROGEN DIFFE- 
RENTTIATES FROM THE CLEAVAGE WHICH OCCURS IN IMPACT TESTS, SHOWING A HIGHER RIVER MAR~ 
KING ASPECT. THESE CLEAVAGE FACETS ARE NUCLEATED MAINLY FROM DIMPLES DEVELOPED AROUND 
THE GRAPHITE NODULES. IT WAS ALSO OBSERVED THAT INCREASING THE GRAPHITE NODULE NUM- 
BER LEAD TO A DECREASE IN THE HYDROGEN EMBRITTLEMENT TENDENCY. 
Zusammenfassung 
DER EINFLUSS VON WASSERSTOFF AUF DIE MECHANISCHEN EIGENSCHAFTEN UND AUF DAS 
BRUCHVERHALTEN VON FERRITISCHEM, SCHWARZEM TEMPERGUSS UND GUSSEISEN MIT KUGELGRAPHIT 
WURDE UNTERSUCHT. DABEI WURDEN EINE DURCH WASSERSTOFFVERSPRUDUNG VERURSACHTE 
VERMINDERUNG DER BRUCHDEHNUNG SOWIE DIE ÄNDERUNG DER BRUCHSTRUKTUR VOM WABENBRUCH ZUM 
SPALTBRUCH FESTGESTELLT. DIE DURCH WASSERSTOFFVERSPRODUNG INDUZIERTEN SPALTFLECHEN 
UNTERSCHEIDEN SICH VON KERBSCHLAG-BRUCHFLACHEN, INDEM SIE MEHR SPALTLINIEN AUFWEISEN; 
DABEI VERLAUFEN DIE BRUCHVERLAUFSLINIEN STERNFURMI .G VON GRAPHITSPHEROLITHEN NACH 
AUSSEN. BEI ERHUHUNG DER GRAPHITTEILCHEN-ANZAHL WURDE EINE VERMINDERUNG DER NEIGUNG 
ZUR WASSERSTOFFVERSPRUDUNG BEOBACHTET. 
1. Introduction 
The increased need for weight reduction has led to great efforts being made in cas- 
ting product developments. Outstanding examples of these improvements are reported 
(1-2), mainly in cast iron foundry industry. For example, the so-called "high ducti- 
lity cast irons", (blackheart malleable iron and ductile iron) are progressively 
substituting forged and cast steels in many applications, with both technical and 
economic benefits. Specially for safety-critical components of high ductility cast 
irons it is important to know the embrittlement mechanisms of these alloys, in order 
to prevent these occurrences during manufacturing or in use. Several studies were de- 
veloped concerning this subject, investigating different embrittlement mechanisms in 
blackheart malleable iron and in ductile iron (3-5). 
Prakt. Met. Sonderbd. 21 (1990) 
121