HAYNES® 556™ alloy - Haynes International, Inc.

CARBURIZATION RESISTANCEHAYNES ® 556 alloy hasexcellent resistance to carburization,as measured in bothmixed gas exposure tests andpacked graphite exposure tests.Results for these tests arepresented in the followingpages.All results are presented interms of the mass of carbonabsorption per unit area, whichwas obtained from the equationM = C(W/A) where M = themass of carbon absorption perunit area (mg/cm 2 ). C = differencein carbon (weightfraction) before and afterexposure , W = weight of theunexposed specimen (mg) andA = surface area of the specimenexposed to the test environment(cm 2 ).Packed Carburization ResistanceCarbon absorption observed for556 alloy following 500 hourexposure in packed graphite at1800°F (980°C) was negligible,as shown below. Similarresistance was exhibited byHAYNES HR-120 ® alloy. Thisis in contrast to other alloystested, all of which exhibitedmeasurable carbon absorption.In particular, the resistanceto carburization of 556alloy was significantly betterthan that for the stainless steeltype materials.1210500 Hours @ 1800°F (980°C)in packed graphiteCarbon Absorption (mg/cm 2 )86420HR-120 ®alloy556 TMalloy230 ®alloyalloy601RA330 ®alloy310Stainless253 MA ®alloyMixed Gas Carburization TestsCarbon absorption observed for556 alloy following exposure atboth 1700°F (925°C) and1800°F (980°C) to a carburizinggas mixture was significantlylower than that for most othermaterials tested. This is shownin the graphs on the followingpages. For these tests, theexposure was performed in agas environment consisting of(by volume %) 5.0% H 2, 5.0%CO, 5.0% CH 4and the balanceargon. The calculated equilibriumcomposition (volume %) at1800°F (980°C) and one atmwas 14.2% H 2, 4.8%CO,0.003% CO 2, 0.026% CH 4,0.011% H 2O and the balanceargon. The activity of carbonwas 1.0 and the partial pressureof oxygen was 9 x 10 -22 atm at1800°F (980°C).HAYNES ® 556 TM alloy 6