Supersolidus Sintering of Cr Prealloyed Steels by Inductive Heating

Abstract

For powder metallurgy products, high density is an essential requirements to obtain maximum mechanical properties. Here, supersolidus liquid phase sintering (SSPLS) is an effective means to attain high sintered density, as known from PM high speed steels. In the present work it is shown that this technique can also be applied to Cr prealloyed low alloy steel grades. Supersolidus sintering through indirect heating requires precise control of temperature and also the atmosphere, to avoid uncontrolled changes of the carbon level. Higher C contents are beneficial here since they enable lower temperatures and result in wider temperature windows for sintering. The temperatures necessary for SSLPS at moderate C levels are fairly high for standard sintering furnaces, therefore induction sintering was studied in this work. It showed that, as was to be expected, also here precise temperature control is required, but for any carbon level tested a sintering temperature could be identified that yielded high sintered density and good shape retention. The high density attained, in combination with the very high temperatures, results in pronounced grain growth, this process no more being inhibited by the presence of pores, which is undesirable but can however be remedied by suitable heat treatment.

Manganese – a promising element also in high alloy sintered steels

“…Today, such parts are produced by sintering, surface rolling and then thermochemical heat treatment such as carburising or carbonitriding [47]. When using the TRIP effect it might be feasible to combine densification and surface hardening by using the transformation to martensite occurring during deformation to increase the surface hardness [48].…”

Archives of Metallurgy and Materials

“…During last 70 years, sintered manganese steels, especially structural PM steels, have been the interests of scientists from all over the world. The main objects of the researches concerned: a) the effect of Mn concentration and other alloying elements on the mechanical properties of PM structural parts, b) the effect of alloying elements, on the microstructure and mechanical properties of sintered Mn steels and c) elimination of Ni and Cu by introducing in sintered steels Mn and Cr causing to increase the mechanical properties of PM Mn steels [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”