As regard a valid marriage as per law, there arises n exists (express n implied) consent of a wife for all marital rights of a hub over her once she consented to contract marriage with him and she cannot retract that back unless she gets divorce r judicially separated. As this the position, there is no question of forced s*x unless there is an order of judicially separated. So u cannot be charged for rape (provided wife must not be under 15 years of age).
And now regarding S.498A, act of s*x without consent of wife does not come within the meaning of cruelty unless it is coupled with any wilful act of causing injury to her while consummation. it is marital duty of wife n marital right of hub to consummate. Once marriage tie exists, there is consent of wife to consummate with her hub even if she not desire to have intercourse. But if hub r his relatives cause any physical r mental cruelty to wife, then S.498A is attracted.
Summarily, consummation without consent of wife is not cruelty but if it is done with any bodily injury r mental injury (for eg., insisting r taunting her prior conduct before marriage n thereby having r forcing to have s*x r while havin s*x ) amounts to cruelty u/s.498A.