33) The process of increasing carbon percentage on the surface of Low-carbon steel is known as

34) The process of producing a component with tough and ductile core and a hard outer surface is known as

35) The process of heating steel to about 40 Degree Centigrade above the upper critical temperature and cooling it in still air to room temperature is known as

36) Which one of the following heat treatment processes produces a scale-free surface on the component ?

37) In heat treatment process annealing is done to