THE EFFECTS OF SURFACE HARDENING ON FRACTURE TOUGHNESS OF CARBURIZED STEEL,

Abstract:
AISI 8620 STEEL WAS MACHINED INTO COMPACT-TENSION (CT) SPECIMENS. THE SPECIMENS WERE PACK CARBURIZED AT 930 C FOR DIFFERENT PERIODS OF TIME, COOLED TO AMBIENT TEMPERATURE AND SUBSEQUENTLY TEMPERED AT VARIOUS TEMPERATURES FOR ONE HOUR. THE FRACTURED SPECIMENS WERE EXAMINED BY HARDNESS TESTS, METALLOGRAPHY, X-RAY DIFFRACTION ANALYSIS FOR RETAINED AUSTENITE IN THE CASE, AND SCANNING ELECTRON MICROSCOPY FRACTOGRAPHIC ANALYSIS OF THE FRACTURE SURFACES. THE EXPERIMENTAL RESULTS REVEALED THAT THE K(SUB IC) VALUES OF THE CARBURIZED AISI 8620 STEELS WERE IMPROVED BY THE INCREASE IN CASE DEPTH. MARTENSITIC/TEMPERED-MARTENSITIC STRUCTURE IN THE CASE WAS THE MAJOR CONSTITUENT CONTRIBUTING TO THE IMPROVED TOUGHNESS. THE AMOUNT OF RETAINED AUSTENITE AT THE CASE INCREASED AS THE THICKNESS OF THE HARDENED LAYER INCREASED. BUT RETAINED AUSTENITE AS WELL AS LARGE GRAIN SIZE WERE FOUND TO HAVE ADVERSE EFFECTS ON FRACTURE TOUGHNESS OF THE CARBURIZED STEEL. THE TEMPERING TEMPERATURE OF 500 C PROVIDED MAXIMUM K(SUB IC) VALUES. HIGHER TEMPERING TEMPERATURES RESULTED IN SHARP DECREASE OF FRACTURE TOUGHNESS VALUES. TERMS: M--(U)COUNTRY TAIWAN, CARBURIZING, FRACTURE MCIC--JOURNAL ARTICLES TOUGHNESS, HARDENING, SURFACE LAYERS, AISI 8620, ENGINEERING STEEL, TEMPERING, OIL QUENCHING, HARDNESS, AUSTENITE, SCANNING ELECTRON MICROSCOPY, X-RAY DIFFRACTION, FRACTOGRAPHY, K(SUB IC), CASE HARDENING, MARTENSITE, TEMPERATURE EFFECT.;

  • PUBLICATION DATE:  01 Jan 1989
  • AUTHORS:  LEE, S-C. HO, W-Y
  • AD/LD ORDER NO:  AD-D140870
  • LOCATION/DAN:  MCIC /B135294  (For Internal Use)

[from Advanced Materials, Manufacturing, and Testing Information Analysis Center]
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