Component or coupon for being used under high thermal and stress load and method for manufacturing such component or coupon

The invention relates to a component or coupon (26), which component or coupon (26) is used in a thermal machine under extreme thermal and mechanical conditions, whereby said component or coupon (26) is made of an alloy material with a controllable grain size (d), and is in service subjected to an expected temperature and/or stress and/or strain distribution (T(X,Y,Z); Ã(X,Y,Z); µ(X,Y,Z)), which varies with the geometrical coordinates (X,Y,Z) of the component or coupon (26). The component or coupon (26) is improved by having a grain size distribution (d(X,Y,Z)), which depends on said expected temperature and/or stress and/or strain distribution (T(X,Y,Z); Ã(X,Y,Z); µ(X,Y,Z)) such that the lifetime of the component (26) is improved with respect to a similar component with a substantially uniform grain size.