Any Android device - be it Lenovo K3 Note or any other manufacturer - can have heating issues. Having such issues does not mean you have got a defective device. Most of the Android devices face the heating up because of the background processes running on your phone. Believe me, majority of these processes are just useless, yet cannot be stopped.
Follow the below mentioned tips to stop or reduce overheating of your phone -
1. Disable all the apps you do not use. Most of the bloat ware that comes with the phone is never used. Android has always earned a bad name due to a big number of unwanted apps. Since you have no way to uninstall them, just disable them.
2. Games - especially the resource hungry ones like Temple Run and the extensive prolonged Web browsing can cause the phone to heat up. Limit your time spent on such activities. After all, it does not have a fan like your PC.
3. Use better batteries. Do not go for cheaper third party batteries. They may not give you the kind of performance expected.
4. Use original chargers. Use only those meant for your phone. Avoid any activity while charging.
5. Use thinner covers for your phone. Bulky and heavy cases and covers may hinder the ventilation.
6. Avoid using higher brightness. It will cause more load on processor and thereby can heat your phone up. Use a anti glare screen protector instead.
Live....and Let Live!