It is difficult to make broad generalizations when it comes to lower bainite vs martensite. Lower bainite and martensite are actually incredibly similar from a microstructure standpoint, they can be difficult to distinguish without electron microscopy. During tempering of martensite small transition carbides are precipitated within the martensite which slowly transforms the martensite to a phase which looks more and more like ferrite, reducing strength and increasing toughness. With bainite, the carbides precipitate during formation. So the sheaves/laths look very similar but the carbides are randomly oriented in martensite but are ordered in the same orientation in bainite. In summary, the two phases would be expected to have similar properties, depending on the degree of tempering in the martensite.
Things become more complicated when it comes to different alloys, where composition will have an impact on bainite and martensite properties. Many journal articles compare bainite at lower hardness to tempered martensite where we would of course expect a toughness improvement with lower hardness. And temperature selection during bainite formation will affect the toughness and hardness as well. There are seemingly contradictory conclusions because of these complicating factors. For example, the article cited in the first post in this thread states that they found an improvement in yield stress by using bainite, while this paper states that they found lower yield stress with bainite:
http://www.sciencedirect.com/science/article/pii/S0254058407005081 Yield stress is the property that controls whether an edge rolls at low force. However, in general yield stress is high with bainite as it is with martensite. It's not the difference between very low yield stress and very high, the difference is smaller than that.
Without the ability to do impact testing, one would never know if a bainite heat treatment was leading to superior properties compared to quench and tempered.
A couple other things brought up in this thread:
1) Marquenching and austempering seem similar on the surface, but the purpose of the two treatments are different. Marquenching can be performed with no formation of bainite whatsoever. Marquenching is performed to equalize the temperature prior to martensite formation so that internal stresses are reduced. Because otherwise martensite forms first on the surface while austenite is contained internally. Martensite is a different size than austenite so this size differences leads to strain.
2) Austempering to achieve bainite is seen in the knife community as the "fancy," or expensive heat treatment. However in many industries austempering is performed to lower cost as it is a one step process instead of quenching and having separate multiple tempers.
3) Making statements about bainite versus martensite "lattice thickness" and therefore making conclusions about how fine an edge a knife can hold are pure speculation. First of all, "lattice thickness" can't be what is being referred to as 250 nm is much too large for atomic spacing. Furthermore, there is no evidence to indicate that bainite is in any way worse at supporting a fine edge. And claiming that the ferrite in lower bainite is less than 20Rc is a misunderstanding of how strengthening mechanisms work in materials.
