Which of the following powder production methods produces spongy and porous particles?

During turning of a low carbon steel bar with TiN coated carbide insert, one needs to improve surface finish without sacrificing material removal rate. To achieve improved surface finish one should

During open die forging process using two flat and parallel dies, a solid steel disc of initial radius $$({R_{IN}})\,\,200mm$$ and Initial height $$({H_{IN}})\,\,50mm$$ attains a height $$({H_{FN}})$$ of $$30mm$$ and radius of $${R_{FN}}$$. Along the die-disc interfaces

(i) The coefficient of friction $$\left( \mu \right)$$ is :
$$\,\,\,\,\,\,\,\mu = 0.35\left[ {1 + {e^{ - {R_{IN}}/{R_{FN}}}}} \right]$$

(ii) In the region $${R_{SS}}\,\, \le \,\,r\,\, \le \,\,{R_{FN}},$$ sliding friction prevails and
$$\,\,\,\,\,\,P = \sqrt 3 .K.{e^{2\mu \left( {{R_{IN}} - r} \right)/{H_{FN}}}}$$ and $$\tau = \mu \,p$$

Where $$p$$ and $$\tau $$ are the normal and the shear stress respectively; $$K$$ is the shear yield strength of steel and $$r$$ is the radial distance of any point
(i) In the region $$0\, \le \,r\, \le \,{R_{IN}}.$$ sticking condition prevails

The value of $$RSS$$ (in $$mm$$ ), where sticking condition changes to sliding friction is

In a rolling process, the roll separating force can be decreased by