| Title |
Surface hardening and Microstructural Refinement of M2 tool Steel by Laser Melting and Electron Bean melting and Subsequent heat Treatments |
| Abstract |
The tool steel M-2 was laser surface melted and the microstructures characterized both in the as-melted and subsequently heat-treated condition. The laser melting resulted in the formation of extremely fine microstructures and nearly complete dissolution of carbides. Electron diffraction studies, when compared with previous X-ray analysis, show that the melt region consists of δ-ferrite and austenite formed by nonequilibrium peritectic reaction. The relative amounts of δ and γ vary with position, the top melt region being mostly of δ and the lower melt region predominantly γ. A most important finding is the microstructural change giving rise to a substantial increase in hardness by subsequent conventional heat treatment: ultra-fine carbide particles are formed throughout the melt region which gives a uniform microstructure with a maximum hardness of 1,070 V.H.N. Prelimenary experiments show that electron beam melting may lend itself to the sauce results. |