Some equipment in the game can have their attack or defense raised as high as 100 (but no higher). It requires certain skill ranks (13 casting for the halberd, for example) and recipe books to attempt this feat, and the higher you raise the equipment's stats, the greater the chance of it simply breaking and being removed from your inventory entirely.
Certain Oxford skills (Increase Production Success Rate 1 through 4, Item Improvement Techniques), the Workship skill on your ship, as well an aide with 100 Paymaster traits, can help increase the likelihood of your success. There is also the
Master's Secret item from the Astro Shop which guarantees a great success to avoid breaking the equipment at higher levels of attack/defense; they cost 59 Astros, or you can buy them from players (who always set their own prices).