Why is martensite hard

Kikumoto, H. Saito, T. Sekine, T. Ogawa, S. Morito, and T. Tanaka, R. Konishi, T. Furuhara, and and T. ASM 60 : Benscoter, and G.

AIME 70, no. De Keijser, and E. View all posts by Larrin. Nice article. Thought you might like this paper. Keep up the good work. So hardness increases with carbon dissolved in BCC tetragonal iron, not the amount of carbon in the steel? Or does it once again harden more once you get to plate martensite only?

And if so do we just get more easily hardening steels when the carbon content is above 0. The carbon has to be present within the martensite to increase its hardness.

If the carbon is present as cementite or other carbides then it will not increase the hardness of the martensite. Plate martensite is not softer than lath martensite. So why the decrease in hardness noted by the experiment? And why is 0. And how does this relate to the comment that plate martensite is weaker than lath martensite and the combo between lath and plate martensite is also considered weaker because ithe boundary between lath and plate often thought to be weaker?

There was a drop in dislocation density but not in hardness. See the figure near the bottom of the article that shows hardness vs carbon content. Hardness does start to plateau around 0. You might mean 0. Hi, when the apex is overheated during sharpening, and loses a few points HRC, how does that happen? Hi, Are there any easier posts related to this one for me to start with? This is a bit too hard for me as I am still a high school student in UK.

Their lack of toughness meant that they could not absorb much of an impact before fracturing. Want to learn more about steel metallurgy? See our metallurgy courses page. Tempering is used to improve toughness in steel that has been through hardened by heating it to form austenite and then quenching it to form martensite.

At these temperatures the martensite decomposes to form iron carbide particles. The higher the temperature, the faster the decomposition for any given period of time. The micrograph shows a steel after substantial tempering. The black particles are iron carbide. Untempered martensite is a strong, hard, brittle material.

The stronger and harder it is, the more brittle it is. The large increase in volume that results creates a highly stressed structure. This is why Martensite has a higher hardness than Austenite for the exact same chemistry….

Blog at WordPress. Speaking of Precision Blog Sensemaking for the precision machining industry. Martensite- Five Facts March 15, 1 Martensite is the hardest and most brittle microstructure obtainable in a given steel. Miles Free. Click Here to Email Me.